/Users/deen/code/yugabyte-db/src/postgres/src/backend/optimizer/path/indxpath.c

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/*-------------------------------------------------------------------------
 *
 * indxpath.c
 *    Routines to determine which indexes are usable for scanning a
 *    given relation, and create Paths accordingly.
 *
 * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/path/indxpath.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <math.h>

#include "access/stratnum.h"
#include "access/sysattr.h"
#include "catalog/pg_am.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_opfamily.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "pg_yb_utils.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/predtest.h"
#include "optimizer/prep.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/var.h"
#include "utils/builtins.h"
#include "utils/bytea.h"
#include "utils/lsyscache.h"
#include "utils/pg_locale.h"
#include "utils/rel.h"
#include "utils/selfuncs.h"


/* XXX see PartCollMatchesExprColl */
#define IndexCollMatchesExprColl(idxcollation, exprcollation) \
  ((idxcollation) == 148kInvalidOid148k || (idxcollation) == (exprcollation)7.71k)

/* Whether we are looking for plain indexscan, bitmap scan, or either */
typedef enum
{
  ST_INDEXSCAN,       /* must support amgettuple */
  ST_BITMAPSCAN,        /* must support amgetbitmap */
  ST_ANYSCAN          /* either is okay */
} ScanTypeControl;

/* Data structure for collecting qual clauses that match an index */
typedef struct
{
  bool    nonempty;   /* True if lists are not all empty */
  /* Lists of RestrictInfos, one per index column */
  List     *indexclauses[INDEX_MAX_KEYS];
} IndexClauseSet;

/* Per-path data used within choose_bitmap_and() */
typedef struct
{
  Path     *path;     /* IndexPath, BitmapAndPath, or BitmapOrPath */
  List     *quals;      /* the WHERE clauses it uses */
  List     *preds;      /* predicates of its partial index(es) */
  Bitmapset  *clauseids;    /* quals+preds represented as a bitmapset */
  bool    unclassifiable; /* has too many quals+preds to process? */
} PathClauseUsage;

/* Callback argument for ec_member_matches_indexcol */
typedef struct
{
  IndexOptInfo *index;    /* index we're considering */
  int     indexcol;   /* index column we want to match to */
} ec_member_matches_arg;


static void consider_index_join_clauses(PlannerInfo *root, RelOptInfo *rel,
              IndexOptInfo *index,
              IndexClauseSet *rclauseset,
              IndexClauseSet *jclauseset,
              IndexClauseSet *eclauseset,
              List **bitindexpaths);
static void consider_index_join_outer_rels(PlannerInfo *root, RelOptInfo *rel,
                 IndexOptInfo *index,
                 IndexClauseSet *rclauseset,
                 IndexClauseSet *jclauseset,
                 IndexClauseSet *eclauseset,
                 List **bitindexpaths,
                 List *indexjoinclauses,
                 int considered_clauses,
                 List **considered_relids);
static void get_join_index_paths(PlannerInfo *root, RelOptInfo *rel,
           IndexOptInfo *index,
           IndexClauseSet *rclauseset,
           IndexClauseSet *jclauseset,
           IndexClauseSet *eclauseset,
           List **bitindexpaths,
           Relids relids,
           List **considered_relids);
static bool eclass_already_used(EquivalenceClass *parent_ec, Relids oldrelids,
          List *indexjoinclauses);
static bool bms_equal_any(Relids relids, List *relids_list);
static void get_index_paths(PlannerInfo *root, RelOptInfo *rel,
        IndexOptInfo *index, IndexClauseSet *clauses,
        List **bitindexpaths);
static List *build_index_paths(PlannerInfo *root, RelOptInfo *rel,
          IndexOptInfo *index, IndexClauseSet *clauses,
          bool useful_predicate,
          ScanTypeControl scantype,
          bool *skip_nonnative_saop,
          bool *skip_lower_saop);
static List *build_paths_for_OR(PlannerInfo *root, RelOptInfo *rel,
           List *clauses, List *other_clauses);
static List *generate_bitmap_or_paths(PlannerInfo *root, RelOptInfo *rel,
             List *clauses, List *other_clauses);
static Path *choose_bitmap_and(PlannerInfo *root, RelOptInfo *rel,
          List *paths);
static int  path_usage_comparator(const void *a, const void *b);
static Cost bitmap_scan_cost_est(PlannerInfo *root, RelOptInfo *rel,
           Path *ipath);
static Cost bitmap_and_cost_est(PlannerInfo *root, RelOptInfo *rel,
          List *paths);
static PathClauseUsage *classify_index_clause_usage(Path *path,
              List **clauselist);
static void find_indexpath_quals(Path *bitmapqual, List **quals, List **preds);
static int  find_list_position(Node *node, List **nodelist);
static bool check_index_only(RelOptInfo *rel, IndexOptInfo *index);
static double get_loop_count(PlannerInfo *root, Index cur_relid, Relids outer_relids);
static double adjust_rowcount_for_semijoins(PlannerInfo *root,
                Index cur_relid,
                Index outer_relid,
                double rowcount);
static double approximate_joinrel_size(PlannerInfo *root, Relids relids);
static void match_restriction_clauses_to_index(RelOptInfo *rel,
                   IndexOptInfo *index,
                   IndexClauseSet *clauseset);
static void match_join_clauses_to_index(PlannerInfo *root,
              RelOptInfo *rel, IndexOptInfo *index,
              IndexClauseSet *clauseset,
              List **joinorclauses);
static void match_eclass_clauses_to_index(PlannerInfo *root,
                IndexOptInfo *index,
                IndexClauseSet *clauseset);
static void match_clauses_to_index(IndexOptInfo *index,
             List *clauses,
             IndexClauseSet *clauseset);
static void match_clause_to_index(IndexOptInfo *index,
            RestrictInfo *rinfo,
            IndexClauseSet *clauseset);
static bool match_clause_to_indexcol(IndexOptInfo *index,
             int indexcol,
             RestrictInfo *rinfo);
static bool is_indexable_operator(Oid expr_op, Oid opfamily,
            bool indexkey_on_left);
static bool match_rowcompare_to_indexcol(IndexOptInfo *index,
               int indexcol,
               Oid opfamily,
               Oid idxcollation,
               RowCompareExpr *clause);
static void match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
            List **orderby_clauses_p,
            List **clause_columns_p);
static Expr *match_clause_to_ordering_op(IndexOptInfo *index,
              int indexcol, Expr *clause, Oid pk_opfamily);
static bool ec_member_matches_indexcol(PlannerInfo *root, RelOptInfo *rel,
               EquivalenceClass *ec, EquivalenceMember *em,
               void *arg);
static bool match_boolean_index_clause(Node *clause, int indexcol,
               IndexOptInfo *index);
static bool match_special_index_operator(Expr *clause,
               Oid opfamily, Oid idxcollation,
               bool indexkey_on_left);
static Expr *expand_boolean_index_clause(Node *clause, int indexcol,
              IndexOptInfo *index);
static List *expand_indexqual_opclause(RestrictInfo *rinfo,
              Oid opfamily, Oid idxcollation);
static RestrictInfo *expand_indexqual_rowcompare(RestrictInfo *rinfo,
              IndexOptInfo *index,
              int indexcol);
static List *prefix_quals(Node *leftop, Oid opfamily, Oid collation,
       Const *prefix, Pattern_Prefix_Status pstatus);
static List *network_prefix_quals(Node *leftop, Oid expr_op, Oid opfamily,
           Datum rightop);
static Datum string_to_datum(const char *str, Oid datatype);
static Const *string_to_const(const char *str, Oid datatype);


/*
 * create_index_paths()
 *    Generate all interesting index paths for the given relation.
 *    Candidate paths are added to the rel's pathlist (using add_path).
 *
 * To be considered for an index scan, an index must match one or more
 * restriction clauses or join clauses from the query's qual condition,
 * or match the query's ORDER BY condition, or have a predicate that
 * matches the query's qual condition.
 *
 * There are two basic kinds of index scans.  A "plain" index scan uses
 * only restriction clauses (possibly none at all) in its indexqual,
 * so it can be applied in any context.  A "parameterized" index scan uses
 * join clauses (plus restriction clauses, if available) in its indexqual.
 * When joining such a scan to one of the relations supplying the other
 * variables used in its indexqual, the parameterized scan must appear as
 * the inner relation of a nestloop join; it can't be used on the outer side,
 * nor in a merge or hash join.  In that context, values for the other rels'
 * attributes are available and fixed during any one scan of the indexpath.
 *
 * An IndexPath is generated and submitted to add_path() for each plain or
 * parameterized index scan this routine deems potentially interesting for
 * the current query.
 *
 * 'rel' is the relation for which we want to generate index paths
 *
 * Note: check_index_predicates() must have been run previously for this rel.
 *
 * Note: in cases involving LATERAL references in the relation's tlist, it's
 * possible that rel->lateral_relids is nonempty.  Currently, we include
 * lateral_relids into the parameterization reported for each path, but don't
 * take it into account otherwise.  The fact that any such rels *must* be
 * available as parameter sources perhaps should influence our choices of
 * index quals ... but for now, it doesn't seem worth troubling over.
 * In particular, comments below about "unparameterized" paths should be read
 * as meaning "unparameterized so far as the indexquals are concerned".
 */
void
create_index_paths(PlannerInfo *root, RelOptInfo *rel)
{
  List     *indexpaths;
  List     *bitindexpaths;
  List     *bitjoinpaths;
  List     *joinorclauses;
  IndexClauseSet rclauseset;
  IndexClauseSet jclauseset;
  IndexClauseSet eclauseset;
  ListCell   *lc;

  /* Skip the whole mess if no indexes */
  if (rel->indexlist == NIL)
    return;

  /* Bitmap paths are collected and then dealt with at the end */
  bitindexpaths = bitjoinpaths = joinorclauses = NIL;

  /* Examine each index in turn */
  foreach(lc, rel->indexlist)
  {
    IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);

    /* Protect limited-size array in IndexClauseSets */
    Assert(index->ncolumns <= INDEX_MAX_KEYS);

    /*
     * Ignore partial indexes that do not match the query.
     * (generate_bitmap_or_paths() might be able to do something with
     * them, but that's of no concern here.)
     */
    if (index->indpred != NIL && !index->predOK321)
      continue;

    /*
     * Identify the restriction clauses that can match the index.
     */
    MemSet(&rclauseset, 0, sizeof(rclauseset));
    match_restriction_clauses_to_index(rel, index, &rclauseset);

    /*
     * Build index paths from the restriction clauses.  These will be
     * non-parameterized paths.  Plain paths go directly to add_path(),
     * bitmap paths are added to bitindexpaths to be handled below.
     */
    get_index_paths(root, rel, index, &rclauseset,
            &bitindexpaths);

    /*
     * Identify the join clauses that can match the index.  For the moment
     * we keep them separate from the restriction clauses.  Note that this
     * step finds only "loose" join clauses that have not been merged into
     * EquivalenceClasses.  Also, collect join OR clauses for later.
     */
    MemSet(&jclauseset, 0, sizeof(jclauseset));
    match_join_clauses_to_index(root, rel, index,
                  &jclauseset, &joinorclauses);

    /*
     * Look for EquivalenceClasses that can generate joinclauses matching
     * the index.
     */
    MemSet(&eclauseset, 0, sizeof(eclauseset));
    match_eclass_clauses_to_index(root, index,
                    &eclauseset);

    /*
     * If we found any plain or eclass join clauses, build parameterized
     * index paths using them.
     */
    if (jclauseset.nonempty || eclauseset.nonempty218k)
      consider_index_join_clauses(root, rel, index,
                    &rclauseset,
                    &jclauseset,
                    &eclauseset,
                    &bitjoinpaths);
  }

  /*
   * Generate BitmapOrPaths for any suitable OR-clauses present in the
   * restriction list.  Add these to bitindexpaths.
   */
  indexpaths = generate_bitmap_or_paths(root, rel,
                      rel->baserestrictinfo, NIL);
  bitindexpaths = list_concat(bitindexpaths, indexpaths);

  /*
   * Likewise, generate BitmapOrPaths for any suitable OR-clauses present in
   * the joinclause list.  Add these to bitjoinpaths.
   */
  indexpaths = generate_bitmap_or_paths(root, rel,
                      joinorclauses, rel->baserestrictinfo);
  bitjoinpaths = list_concat(bitjoinpaths, indexpaths);

  /*
   * If we found anything usable, generate a BitmapHeapPath for the most
   * promising combination of restriction bitmap index paths.  Note there
   * will be only one such path no matter how many indexes exist.  This
   * should be sufficient since there's basically only one figure of merit
   * (total cost) for such a path.
   */
  if (bitindexpaths != NIL)
  {
    Path     *bitmapqual;
    BitmapHeapPath *bpath;

    bitmapqual = choose_bitmap_and(root, rel, bitindexpaths);
    bpath = create_bitmap_heap_path(root, rel, bitmapqual,
                    rel->lateral_relids, 1.0, 0);
    add_path(rel, (Path *) bpath);

    /* create a partial bitmap heap path */
    if (rel->consider_parallel && rel->lateral_relids == NULL0)
      create_partial_bitmap_paths(root, rel, bitmapqual);
  }

  /*
   * Likewise, if we found anything usable, generate BitmapHeapPaths for the
   * most promising combinations of join bitmap index paths.  Our strategy
   * is to generate one such path for each distinct parameterization seen
   * among the available bitmap index paths.  This may look pretty
   * expensive, but usually there won't be very many distinct
   * parameterizations.  (This logic is quite similar to that in
   * consider_index_join_clauses, but we're working with whole paths not
   * individual clauses.)
   */
  if (bitjoinpaths != NIL)
  {
    List     *all_path_outers;
    ListCell   *lc;

    /* Identify each distinct parameterization seen in bitjoinpaths */
    all_path_outers = NIL;
    foreach(lc, bitjoinpaths)
    {
      Path     *path = (Path *) lfirst(lc);
      Relids    required_outer = PATH_REQ_OUTER(path);

      if (!bms_equal_any(required_outer, all_path_outers))
        all_path_outers = lappend(all_path_outers, required_outer);
    }

    /* Now, for each distinct parameterization set ... */
    foreach(lc, all_path_outers)
    {
      Relids    max_outers = (Relids) lfirst(lc);
      List     *this_path_set;
      Path     *bitmapqual;
      Relids    required_outer;
      double    loop_count;
      BitmapHeapPath *bpath;
      ListCell   *lcp;

      /* Identify all the bitmap join paths needing no more than that */
      this_path_set = NIL;
      foreach(lcp, bitjoinpaths)
      {
        Path     *path = (Path *) lfirst(lcp);

        if (bms_is_subset(PATH_REQ_OUTER(path), max_outers))
          this_path_set = lappend(this_path_set, path);
      }

      /*
       * Add in restriction bitmap paths, since they can be used
       * together with any join paths.
       */
      this_path_set = list_concat(this_path_set, bitindexpaths);

      /* Select best AND combination for this parameterization */
      bitmapqual = choose_bitmap_and(root, rel, this_path_set);

      /* And push that path into the mix */
      required_outer = PATH_REQ_OUTER(bitmapqual);
      loop_count = get_loop_count(root, rel->relid, required_outer);
      bpath = create_bitmap_heap_path(root, rel, bitmapqual,
                      required_outer, loop_count, 0);
      add_path(rel, (Path *) bpath);
    }
  }
}

/*
 * consider_index_join_clauses
 *    Given sets of join clauses for an index, decide which parameterized
 *    index paths to build.
 *
 * Plain indexpaths are sent directly to add_path, while potential
 * bitmap indexpaths are added to *bitindexpaths for later processing.
 *
 * 'rel' is the index's heap relation
 * 'index' is the index for which we want to generate paths
 * 'rclauseset' is the collection of indexable restriction clauses
 * 'jclauseset' is the collection of indexable simple join clauses
 * 'eclauseset' is the collection of indexable clauses from EquivalenceClasses
 * '*bitindexpaths' is the list to add bitmap paths to
 */
static void
consider_index_join_clauses(PlannerInfo *root, RelOptInfo *rel,
              IndexOptInfo *index,
              IndexClauseSet *rclauseset,
              IndexClauseSet *jclauseset,
              IndexClauseSet *eclauseset,
              List **bitindexpaths)
{
  int     considered_clauses = 0;
  List     *considered_relids = NIL;
  int     indexcol;

  /*
   * The strategy here is to identify every potentially useful set of outer
   * rels that can provide indexable join clauses.  For each such set,
   * select all the join clauses available from those outer rels, add on all
   * the indexable restriction clauses, and generate plain and/or bitmap
   * index paths for that set of clauses.  This is based on the assumption
   * that it's always better to apply a clause as an indexqual than as a
   * filter (qpqual); which is where an available clause would end up being
   * applied if we omit it from the indexquals.
   *
   * This looks expensive, but in most practical cases there won't be very
   * many distinct sets of outer rels to consider.  As a safety valve when
   * that's not true, we use a heuristic: limit the number of outer rel sets
   * considered to a multiple of the number of clauses considered.  (We'll
   * always consider using each individual join clause, though.)
   *
   * For simplicity in selecting relevant clauses, we represent each set of
   * outer rels as a maximum set of clause_relids --- that is, the indexed
   * relation itself is also included in the relids set.  considered_relids
   * lists all relids sets we've already tried.
   */
  for (indexcol = 0; indexcol < index->ncolumns; indexcol++13.3k)
  {
    /* Consider each applicable simple join clause */
    considered_clauses += list_length(jclauseset->indexclauses[indexcol]);
    consider_index_join_outer_rels(root, rel, index,
                     rclauseset, jclauseset, eclauseset,
                     bitindexpaths,
                     jclauseset->indexclauses[indexcol],
                     considered_clauses,
                     &considered_relids);
    /* Consider each applicable eclass join clause */
    considered_clauses += list_length(eclauseset->indexclauses[indexcol]);
    consider_index_join_outer_rels(root, rel, index,
                     rclauseset, jclauseset, eclauseset,
                     bitindexpaths,
                     eclauseset->indexclauses[indexcol],
                     considered_clauses,
                     &considered_relids);
  }
}

/*
 * consider_index_join_outer_rels
 *    Generate parameterized paths based on clause relids in the clause list.
 *
 * Workhorse for consider_index_join_clauses; see notes therein for rationale.
 *
 * 'rel', 'index', 'rclauseset', 'jclauseset', 'eclauseset', and
 *    'bitindexpaths' as above
 * 'indexjoinclauses' is a list of RestrictInfos for join clauses
 * 'considered_clauses' is the total number of clauses considered (so far)
 * '*considered_relids' is a list of all relids sets already considered
 */
static void
consider_index_join_outer_rels(PlannerInfo *root, RelOptInfo *rel,
                 IndexOptInfo *index,
                 IndexClauseSet *rclauseset,
                 IndexClauseSet *jclauseset,
                 IndexClauseSet *eclauseset,
                 List **bitindexpaths,
                 List *indexjoinclauses,
                 int considered_clauses,
                 List **considered_relids)
{
  ListCell   *lc;

  /* Examine relids of each joinclause in the given list */
  foreach(lc, indexjoinclauses)
  {
    RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
    Relids    clause_relids = rinfo->clause_relids;
    ListCell   *lc2;

    /* If we already tried its relids set, no need to do so again */
    if (bms_equal_any(clause_relids, *considered_relids))
      continue;

    /*
     * Generate the union of this clause's relids set with each
     * previously-tried set.  This ensures we try this clause along with
     * every interesting subset of previous clauses.  However, to avoid
     * exponential growth of planning time when there are many clauses,
     * limit the number of relid sets accepted to 10 * considered_clauses.
     *
     * Note: get_join_index_paths adds entries to *considered_relids, but
     * it prepends them to the list, so that we won't visit new entries
     * during the inner foreach loop.  No real harm would be done if we
     * did, since the subset check would reject them; but it would waste
     * some cycles.
     */
    foreach(lc2, *considered_relids)
    {
      Relids    oldrelids = (Relids) lfirst(lc2);

      /*
       * If either is a subset of the other, no new set is possible.
       * This isn't a complete test for redundancy, but it's easy and
       * cheap.  get_join_index_paths will check more carefully if we
       * already generated the same relids set.
       */
      if (bms_subset_compare(clause_relids, oldrelids) != BMS_DIFFERENT)
        continue;

      /*
       * If this clause was derived from an equivalence class, the
       * clause list may contain other clauses derived from the same
       * eclass.  We should not consider that combining this clause with
       * one of those clauses generates a usefully different
       * parameterization; so skip if any clause derived from the same
       * eclass would already have been included when using oldrelids.
       */
      if (rinfo->parent_ec &&
        eclass_already_used(rinfo->parent_ec, oldrelids,
                  indexjoinclauses))
        continue;

      /*
       * If the number of relid sets considered exceeds our heuristic
       * limit, stop considering combinations of clauses.  We'll still
       * consider the current clause alone, though (below this loop).
       */
      if (list_length(*considered_relids) >= 10 * considered_clauses)
        break;

      /* OK, try the union set */
      get_join_index_paths(root, rel, index,
                 rclauseset, jclauseset, eclauseset,
                 bitindexpaths,
                 bms_union(clause_relids, oldrelids),
                 considered_relids);
    }

    /* Also try this set of relids by itself */
    get_join_index_paths(root, rel, index,
               rclauseset, jclauseset, eclauseset,
               bitindexpaths,
               clause_relids,
               considered_relids);
  }
}

/*
 * get_join_index_paths
 *    Generate index paths using clauses from the specified outer relations.
 *    In addition to generating paths, relids is added to *considered_relids
 *    if not already present.
 *
 * Workhorse for consider_index_join_clauses; see notes therein for rationale.
 *
 * 'rel', 'index', 'rclauseset', 'jclauseset', 'eclauseset',
 *    'bitindexpaths', 'considered_relids' as above
 * 'relids' is the current set of relids to consider (the target rel plus
 *    one or more outer rels)
 */
static void
get_join_index_paths(PlannerInfo *root, RelOptInfo *rel,
           IndexOptInfo *index,
           IndexClauseSet *rclauseset,
           IndexClauseSet *jclauseset,
           IndexClauseSet *eclauseset,
           List **bitindexpaths,
           Relids relids,
           List **considered_relids)
{
  IndexClauseSet clauseset;
  int     indexcol;

  /* If we already considered this relids set, don't repeat the work */
  if (bms_equal_any(relids, *considered_relids))
    return;

  /* Identify indexclauses usable with this relids set */
  MemSet(&clauseset, 0, sizeof(clauseset));

  for (indexcol = 0; indexcol < index->ncolumns; indexcol++13.9k)
  {
    ListCell   *lc;

    /* First find applicable simple join clauses */
    foreach(lc, jclauseset->indexclauses[indexcol])
    {
      RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

      if (bms_is_subset(rinfo->clause_relids, relids))
        clauseset.indexclauses[indexcol] =
          lappend(clauseset.indexclauses[indexcol], rinfo);
    }

    /*
     * Add applicable eclass join clauses.  The clauses generated for each
     * column are redundant (cf generate_implied_equalities_for_column),
     * so we need at most one.  This is the only exception to the general
     * rule of using all available index clauses.
     */
    foreach(lc, eclauseset->indexclauses[indexcol])
    {
      RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

      if (bms_is_subset(rinfo->clause_relids, relids))
      {
        clauseset.indexclauses[indexcol] =
          lappend(clauseset.indexclauses[indexcol], rinfo);
        break;
      }
    }

    /* Add restriction clauses (this is nondestructive to rclauseset) */
    clauseset.indexclauses[indexcol] =
      list_concat(clauseset.indexclauses[indexcol],
            rclauseset->indexclauses[indexcol]);

    if (clauseset.indexclauses[indexcol] != NIL)
      clauseset.nonempty = true;
  }

  /* We should have found something, else caller passed silly relids */
  Assert(clauseset.nonempty);

  /* Build index path(s) using the collected set of clauses */
  get_index_paths(root, rel, index, &clauseset, bitindexpaths);

  /*
   * Remember we considered paths for this set of relids.  We use lcons not
   * lappend to avoid confusing the loop in consider_index_join_outer_rels.
   */
  *considered_relids = lcons(relids, *considered_relids);
}

/*
 * eclass_already_used
 *    True if any join clause usable with oldrelids was generated from
 *    the specified equivalence class.
 */
static bool
eclass_already_used(EquivalenceClass *parent_ec, Relids oldrelids,
          List *indexjoinclauses)
{
  ListCell   *lc;

  foreach(lc, indexjoinclauses)
  {
    RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

    if (rinfo->parent_ec == parent_ec &&
      bms_is_subset(rinfo->clause_relids, oldrelids))
      return true;
  }
  return false;
}

/*
 * bms_equal_any
 *    True if relids is bms_equal to any member of relids_list
 *
 * Perhaps this should be in bitmapset.c someday.
 */
static bool
bms_equal_any(Relids relids, List *relids_list)
{
  ListCell   *lc;

  foreach(lc, relids_list)
  {
    if (bms_equal(relids, (Relids) lfirst(lc)))
      return true;
  }
  return false;
}


/*
 * get_index_paths
 *    Given an index and a set of index clauses for it, construct IndexPaths.
 *
 * Plain indexpaths are sent directly to add_path, while potential
 * bitmap indexpaths are added to *bitindexpaths for later processing.
 *
 * This is a fairly simple frontend to build_index_paths().  Its reason for
 * existence is mainly to handle ScalarArrayOpExpr quals properly.  If the
 * index AM supports them natively, we should just include them in simple
 * index paths.  If not, we should exclude them while building simple index
 * paths, and then make a separate attempt to include them in bitmap paths.
 * Furthermore, we should consider excluding lower-order ScalarArrayOpExpr
 * quals so as to create ordered paths.
 */
static void
get_index_paths(PlannerInfo *root, RelOptInfo *rel,
        IndexOptInfo *index, IndexClauseSet *clauses,
        List **bitindexpaths)
{
  List     *indexpaths;
  bool    skip_nonnative_saop = false;
  bool    skip_lower_saop = false;
  ListCell   *lc;

  /*
   * Build simple index paths using the clauses.  Allow ScalarArrayOpExpr
   * clauses only if the index AM supports them natively, and skip any such
   * clauses for index columns after the first (so that we produce ordered
   * paths if possible).
   */
  indexpaths = build_index_paths(root, rel,
                   index, clauses,
                   index->predOK,
                   ST_ANYSCAN,
                   &skip_nonnative_saop,
                   &skip_lower_saop);

  /*
   * If we skipped any lower-order ScalarArrayOpExprs on an index with an AM
   * that supports them, then try again including those clauses.  This will
   * produce paths with more selectivity but no ordering.
   */
  if (skip_lower_saop)
  {
    indexpaths = list_concat(indexpaths,
                 build_index_paths(root, rel,
                           index, clauses,
                           index->predOK,
                           ST_ANYSCAN,
                           &skip_nonnative_saop,
                           NULL));
  }

  /*
   * Submit all the ones that can form plain IndexScan plans to add_path. (A
   * plain IndexPath can represent either a plain IndexScan or an
   * IndexOnlyScan, but for our purposes here that distinction does not
   * matter.  However, some of the indexes might support only bitmap scans,
   * and those we mustn't submit to add_path here.)
   *
   * Also, pick out the ones that are usable as bitmap scans.  For that, we
   * must discard indexes that don't support bitmap scans, and we also are
   * only interested in paths that have some selectivity; we should discard
   * anything that was generated solely for ordering purposes.
   */
  foreach(lc, indexpaths)
  {
    IndexPath  *ipath = (IndexPath *) lfirst(lc);

    if (index->amhasgettuple)
      add_path(rel, (Path *) ipath);

    if (index->amhasgetbitmap &&
      (283ipath->path.pathkeys == 283NIL283 ||
       ipath->indexselectivity < 1.064))
      *bitindexpaths = lappend(*bitindexpaths, ipath);
  }

  /*
   * If there were ScalarArrayOpExpr clauses that the index can't handle
   * natively, generate bitmap scan paths relying on executor-managed
   * ScalarArrayOpExpr.
   */
  if (skip_nonnative_saop)
  {
    indexpaths = build_index_paths(root, rel,
                     index, clauses,
                     false,
                     ST_BITMAPSCAN,
                     NULL,
                     NULL);
    *bitindexpaths = list_concat(*bitindexpaths, indexpaths);
  }
}

/*
 * build_index_paths
 *    Given an index and a set of index clauses for it, construct zero
 *    or more IndexPaths. It also constructs zero or more partial IndexPaths.
 *
 * We return a list of paths because (1) this routine checks some cases
 * that should cause us to not generate any IndexPath, and (2) in some
 * cases we want to consider both a forward and a backward scan, so as
 * to obtain both sort orders.  Note that the paths are just returned
 * to the caller and not immediately fed to add_path().
 *
 * At top level, useful_predicate should be exactly the index's predOK flag
 * (ie, true if it has a predicate that was proven from the restriction
 * clauses).  When working on an arm of an OR clause, useful_predicate
 * should be true if the predicate required the current OR list to be proven.
 * Note that this routine should never be called at all if the index has an
 * unprovable predicate.
 *
 * scantype indicates whether we want to create plain indexscans, bitmap
 * indexscans, or both.  When it's ST_BITMAPSCAN, we will not consider
 * index ordering while deciding if a Path is worth generating.
 *
 * If skip_nonnative_saop is non-NULL, we ignore ScalarArrayOpExpr clauses
 * unless the index AM supports them directly, and we set *skip_nonnative_saop
 * to true if we found any such clauses (caller must initialize the variable
 * to false).  If it's NULL, we do not ignore ScalarArrayOpExpr clauses.
 *
 * If skip_lower_saop is non-NULL, we ignore ScalarArrayOpExpr clauses for
 * non-first index columns, and we set *skip_lower_saop to true if we found
 * any such clauses (caller must initialize the variable to false).  If it's
 * NULL, we do not ignore non-first ScalarArrayOpExpr clauses, but they will
 * result in considering the scan's output to be unordered.
 *
 * 'rel' is the index's heap relation
 * 'index' is the index for which we want to generate paths
 * 'clauses' is the collection of indexable clauses (RestrictInfo nodes)
 * 'useful_predicate' indicates whether the index has a useful predicate
 * 'scantype' indicates whether we need plain or bitmap scan support
 * 'skip_nonnative_saop' indicates whether to accept SAOP if index AM doesn't
 * 'skip_lower_saop' indicates whether to accept non-first-column SAOP
 */
static List *
build_index_paths(PlannerInfo *root, RelOptInfo *rel,
          IndexOptInfo *index, IndexClauseSet *clauses,
          bool useful_predicate,
          ScanTypeControl scantype,
          bool *skip_nonnative_saop,
          bool *skip_lower_saop)
{
  List     *result = NIL;
  IndexPath  *ipath;
  List     *index_clauses;
  List     *clause_columns;
  Relids    outer_relids;
  double    loop_count;
  List     *orderbyclauses;
  List     *orderbyclausecols;
  List     *index_pathkeys;
  List     *useful_pathkeys;
  bool    found_lower_saop_clause;
  bool    pathkeys_possibly_useful;
  bool    index_is_ordered;
  bool    index_only_scan;
  int     indexcol;

  /*
   * Check that index supports the desired scan type(s)
   */
  switch (scantype)
  {
    case ST_INDEXSCAN:
      if (!index->amhasgettuple)
        return NIL;
      break;
    case ST_BITMAPSCAN:
      if (!index->amhasgetbitmap)
        return NIL;
      break;
    case ST_ANYSCAN:
      /* either or both are OK */
      break;
  }

  /*
   * 1. Collect the index clauses into a single list.
   *
   * We build a list of RestrictInfo nodes for clauses to be used with this
   * index, along with an integer list of the index column numbers (zero
   * based) that each clause should be used with.  The clauses are ordered
   * by index key, so that the column numbers form a nondecreasing sequence.
   * (This order is depended on by btree and possibly other places.)  The
   * lists can be empty, if the index AM allows that.
   *
   * found_lower_saop_clause is set true if we accept a ScalarArrayOpExpr
   * index clause for a non-first index column.  This prevents us from
   * assuming that the scan result is ordered.  (Actually, the result is
   * still ordered if there are equality constraints for all earlier
   * columns, but it seems too expensive and non-modular for this code to be
   * aware of that refinement.)
   *
   * We also build a Relids set showing which outer rels are required by the
   * selected clauses.  Any lateral_relids are included in that, but not
   * otherwise accounted for.
   */
  index_clauses = NIL;
  clause_columns = NIL;
  found_lower_saop_clause = false;
  outer_relids = bms_copy(rel->lateral_relids);
  for (indexcol = 0; indexcol < index->ncolumns; indexcol++320k)
  {
    ListCell   *lc;

    foreach(lc, clauses->indexclauses[indexcol])
    {
      RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

      if (IsA(rinfo->clause, ScalarArrayOpExpr))
      {
        if (!index->amsearcharray)
        {
          if (skip_nonnative_saop)
          {
            /* Ignore because not supported by index */
            *skip_nonnative_saop = true;
            continue;
          }
          /* Caller had better intend this only for bitmap scan */
          Assert(scantype == ST_BITMAPSCAN);
        }
        if (indexcol > 0)
        {
          if (skip_lower_saop)
          {
            /* Caller doesn't want to lose index ordering */
            *skip_lower_saop = true;
            continue;
          }
          found_lower_saop_clause = true;
        }
      }
      index_clauses = lappend(index_clauses, rinfo);
      clause_columns = lappend_int(clause_columns, indexcol);
      outer_relids = bms_add_members(outer_relids,
                       rinfo->clause_relids);
    }

    /*
     * If no clauses match the first index column, check for amoptionalkey
     * restriction.  We can't generate a scan over an index with
     * amoptionalkey = false unless there's at least one index clause.
     * (When working on columns after the first, this test cannot fail. It
     * is always okay for columns after the first to not have any
     * clauses.)
     */
    if (index_clauses == NIL && !index->amoptionalkey134k)
      return NIL;
  }

  /* We do not want the index's rel itself listed in outer_relids */
  outer_relids = bms_del_member(outer_relids, rel->relid);
  /* Enforce convention that outer_relids is exactly NULL if empty */
  if (bms_is_empty(outer_relids))
    outer_relids = NULL;

  /* Compute loop_count for cost estimation purposes */
  loop_count = get_loop_count(root, rel->relid, outer_relids);

  /*
   * 2. Compute pathkeys describing index's ordering, if any, then see how
   * many of them are actually useful for this query.  This is not relevant
   * if we are only trying to build bitmap indexscans, nor if we have to
   * assume the scan is unordered.
   */
  pathkeys_possibly_useful = (scantype != ST_BITMAPSCAN &&
                !found_lower_saop_clause231k &&
                has_useful_pathkeys(root, rel)231k);
  index_is_ordered = (index->sortopfamily != NULL);
  if (index_is_ordered && pathkeys_possibly_useful230k)
  {
    index_pathkeys = build_index_pathkeys(root, index,
                        ForwardScanDirection);
    useful_pathkeys = truncate_useless_pathkeys(root, rel,
                          index_pathkeys);
    orderbyclauses = NIL;
    orderbyclausecols = NIL;
  }
  else if (index->amcanorderbyop && pathkeys_possibly_useful3)
  {
    /* see if we can generate ordering operators for query_pathkeys */
    match_pathkeys_to_index(index, root->query_pathkeys,
                &orderbyclauses,
                &orderbyclausecols);
    if (orderbyclauses)
      useful_pathkeys = root->query_pathkeys;
    else
      useful_pathkeys = NIL;
  }
  else
  {
    useful_pathkeys = NIL;
    orderbyclauses = NIL;
    orderbyclausecols = NIL;
  }

  /*
   * 3. Check if an index-only scan is possible.  If we're not building
   * plain indexscans, this isn't relevant since bitmap scans don't support
   * index data retrieval anyway.
   */
  index_only_scan = (scantype != ST_BITMAPSCAN &&
             check_index_only(rel, index)231k);

  /*
   * 4. Generate an indexscan path if there are relevant restriction clauses
   * in the current clauses, OR the index ordering is potentially useful for
   * later merging or final output ordering, OR the index has a useful
   * predicate, OR an index-only scan is possible.
   */
  if (index_clauses != NIL || useful_pathkeys != 118kNIL118k || useful_predicate113k ||
    index_only_scan113k)
  {
    ipath = create_index_path(root, index,
                  index_clauses,
                  clause_columns,
                  orderbyclauses,
                  orderbyclausecols,
                  useful_pathkeys,
                  index_is_ordered ?
                  ForwardScanDirection :
                  NoMovementScanDirection387,
                  index_only_scan,
                  outer_relids,
                  loop_count,
                  false);
    result = lappend(result, ipath);

    /*
     * If appropriate, consider parallel index scan.  We don't allow
     * parallel index scan for bitmap index scans.
     */
    if (index->amcanparallel &&
      rel->consider_parallel230 && outer_relids == NULL0 &&
      scantype != ST_BITMAPSCAN0)
    {
      ipath = create_index_path(root, index,
                    index_clauses,
                    clause_columns,
                    orderbyclauses,
                    orderbyclausecols,
                    useful_pathkeys,
                    index_is_ordered ?
                    ForwardScanDirection :
                    NoMovementScanDirection,
                    index_only_scan,
                    outer_relids,
                    loop_count,
                    true);

      /*
       * if, after costing the path, we find that it's not worth using
       * parallel workers, just free it.
       */
      if (ipath->path.parallel_workers > 0)
        add_partial_path(rel, (Path *) ipath);
      else
        pfree(ipath);
    }
  }

  /*
   * 5. If the index is ordered, a backwards scan might be interesting.
   */
  if (index_is_ordered && pathkeys_possibly_useful231k)
  {
    index_pathkeys = build_index_pathkeys(root, index,
                        BackwardScanDirection);
    useful_pathkeys = truncate_useless_pathkeys(root, rel,
                          index_pathkeys);
    if (useful_pathkeys != NIL)
    {
      ipath = create_index_path(root, index,
                    index_clauses,
                    clause_columns,
                    NIL,
                    NIL,
                    useful_pathkeys,
                    BackwardScanDirection,
                    index_only_scan,
                    outer_relids,
                    loop_count,
                    false);
      result = lappend(result, ipath);

      /* If appropriate, consider parallel index scan */
      if (index->amcanparallel &&
        rel->consider_parallel3 && outer_relids == NULL0 &&
        scantype != ST_BITMAPSCAN0)
      {
        ipath = create_index_path(root, index,
                      index_clauses,
                      clause_columns,
                      NIL,
                      NIL,
                      useful_pathkeys,
                      BackwardScanDirection,
                      index_only_scan,
                      outer_relids,
                      loop_count,
                      true);

        /*
         * if, after costing the path, we find that it's not worth
         * using parallel workers, just free it.
         */
        if (ipath->path.parallel_workers > 0)
          add_partial_path(rel, (Path *) ipath);
        else
          pfree(ipath);
      }
    }
  }

  return result;
}

/*
 * build_paths_for_OR
 *    Given a list of restriction clauses from one arm of an OR clause,
 *    construct all matching IndexPaths for the relation.
 *
 * Here we must scan all indexes of the relation, since a bitmap OR tree
 * can use multiple indexes.
 *
 * The caller actually supplies two lists of restriction clauses: some
 * "current" ones and some "other" ones.  Both lists can be used freely
 * to match keys of the index, but an index must use at least one of the
 * "current" clauses to be considered usable.  The motivation for this is
 * examples like
 *    WHERE (x = 42) AND (... OR (y = 52 AND z = 77) OR ....)
 * While we are considering the y/z subclause of the OR, we can use "x = 42"
 * as one of the available index conditions; but we shouldn't match the
 * subclause to any index on x alone, because such a Path would already have
 * been generated at the upper level.  So we could use an index on x,y,z
 * or an index on x,y for the OR subclause, but not an index on just x.
 * When dealing with a partial index, a match of the index predicate to
 * one of the "current" clauses also makes the index usable.
 *
 * 'rel' is the relation for which we want to generate index paths
 * 'clauses' is the current list of clauses (RestrictInfo nodes)
 * 'other_clauses' is the list of additional upper-level clauses
 */
static List *
build_paths_for_OR(PlannerInfo *root, RelOptInfo *rel,
           List *clauses, List *other_clauses)
{
  List     *result = NIL;
  List     *all_clauses = NIL; /* not computed till needed */
  ListCell   *lc;

  foreach(lc, rel->indexlist)
  {
    IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);
    IndexClauseSet clauseset;
    List     *indexpaths;
    bool    useful_predicate;

    /* Ignore index if it doesn't support bitmap scans */
    if (!index->amhasgetbitmap)
      continue;

    /*
     * Ignore partial indexes that do not match the query.  If a partial
     * index is marked predOK then we know it's OK.  Otherwise, we have to
     * test whether the added clauses are sufficient to imply the
     * predicate. If so, we can use the index in the current context.
     *
     * We set useful_predicate to true iff the predicate was proven using
     * the current set of clauses.  This is needed to prevent matching a
     * predOK index to an arm of an OR, which would be a legal but
     * pointlessly inefficient plan.  (A better plan will be generated by
     * just scanning the predOK index alone, no OR.)
     */
    useful_predicate = false;
    if (index->indpred != NIL)
    {
      if (index->predOK)
      {
        /* Usable, but don't set useful_predicate */
      }
      else
      {
        /* Form all_clauses if not done already */
        if (all_clauses == NIL)
          all_clauses = list_concat(list_copy(clauses),
                        other_clauses);

        if (!predicate_implied_by(index->indpred, all_clauses, false))
          continue; /* can't use it at all */

        if (!predicate_implied_by(index->indpred, other_clauses, false))
          useful_predicate = true;
      }
    }

    /*
     * Identify the restriction clauses that can match the index.
     */
    MemSet(&clauseset, 0, sizeof(clauseset));
    match_clauses_to_index(index, clauses, &clauseset);

    /*
     * If no matches so far, and the index predicate isn't useful, we
     * don't want it.
     */
    if (!clauseset.nonempty && !useful_predicate32)
      continue;

    /*
     * Add "other" restriction clauses to the clauseset.
     */
    match_clauses_to_index(index, other_clauses, &clauseset);

    /*
     * Construct paths if possible.
     */
    indexpaths = build_index_paths(root, rel,
                     index, &clauseset,
                     useful_predicate,
                     ST_BITMAPSCAN,
                     NULL,
                     NULL);
    result = list_concat(result, indexpaths);
  }

  return result;
}

/*
 * generate_bitmap_or_paths
 *    Look through the list of clauses to find OR clauses, and generate
 *    a BitmapOrPath for each one we can handle that way.  Return a list
 *    of the generated BitmapOrPaths.
 *
 * other_clauses is a list of additional clauses that can be assumed true
 * for the purpose of generating indexquals, but are not to be searched for
 * ORs.  (See build_paths_for_OR() for motivation.)
 */
static List *
generate_bitmap_or_paths(PlannerInfo *root, RelOptInfo *rel,
             List *clauses, List *other_clauses)
{
  List     *result = NIL;
  List     *all_clauses;
  ListCell   *lc;

  /*
   * We can use both the current and other clauses as context for
   * build_paths_for_OR; no need to remove ORs from the lists.
   */
  all_clauses = list_concat(list_copy(clauses), other_clauses);

  foreach(lc, clauses)
  {
    RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
    List     *pathlist;
    Path     *bitmapqual;
    ListCell   *j;

    /* Ignore RestrictInfos that aren't ORs */
    if (!restriction_is_or_clause(rinfo))
      continue;

    /*
     * We must be able to match at least one index to each of the arms of
     * the OR, else we can't use it.
     */
    pathlist = NIL;
    foreach(j, ((BoolExpr *) rinfo->orclause)->args)
    {
      Node     *orarg = (Node *) lfirst(j);
      List     *indlist;

      /* OR arguments should be ANDs or sub-RestrictInfos */
      if (and_clause(orarg))
      {
        List     *andargs = ((BoolExpr *) orarg)->args;

        indlist = build_paths_for_OR(root, rel,
                       andargs,
                       all_clauses);

        /* Recurse in case there are sub-ORs */
        indlist = list_concat(indlist,
                    generate_bitmap_or_paths(root, rel,
                                 andargs,
                                 all_clauses));
      }
      else
      {
        RestrictInfo *rinfo = castNode(RestrictInfo, orarg);
        List     *orargs;

        Assert(!restriction_is_or_clause(rinfo));
        orargs = list_make1(rinfo);

        indlist = build_paths_for_OR(root, rel,
                       orargs,
                       all_clauses);
      }

      /*
       * If nothing matched this arm, we can't do anything with this OR
       * clause.
       */
      if (indlist == NIL)
      {
        pathlist = NIL;
        break;
      }

      /*
       * OK, pick the most promising AND combination, and add it to
       * pathlist.
       */
      bitmapqual = choose_bitmap_and(root, rel, indlist);
      pathlist = lappend(pathlist, bitmapqual);
    }

    /*
     * If we have a match for every arm, then turn them into a
     * BitmapOrPath, and add to result list.
     */
    if (pathlist != NIL)
    {
      bitmapqual = (Path *) create_bitmap_or_path(root, rel, pathlist);
      result = lappend(result, bitmapqual);
    }
  }

  return result;
}


/*
 * choose_bitmap_and
 *    Given a nonempty list of bitmap paths, AND them into one path.
 *
 * This is a nontrivial decision since we can legally use any subset of the
 * given path set.  We want to choose a good tradeoff between selectivity
 * and cost of computing the bitmap.
 *
 * The result is either a single one of the inputs, or a BitmapAndPath
 * combining multiple inputs.
 */
static Path *
choose_bitmap_and(PlannerInfo *root, RelOptInfo *rel, List *paths)
{
  int     npaths = list_length(paths);
  PathClauseUsage **pathinfoarray;
  PathClauseUsage *pathinfo;
  List     *clauselist;
  List     *bestpaths = NIL;
  Cost    bestcost = 0;
  int     i,
        j;
  ListCell   *l;

  Assert(npaths > 0);     /* else caller error */
  if (npaths == 1)
    return (Path *) linitial(paths); /* easy case */

  /*
   * In theory we should consider every nonempty subset of the given paths.
   * In practice that seems like overkill, given the crude nature of the
   * estimates, not to mention the possible effects of higher-level AND and
   * OR clauses.  Moreover, it's completely impractical if there are a large
   * number of paths, since the work would grow as O(2^N).
   *
   * As a heuristic, we first check for paths using exactly the same sets of
   * WHERE clauses + index predicate conditions, and reject all but the
   * cheapest-to-scan in any such group.  This primarily gets rid of indexes
   * that include the interesting columns but also irrelevant columns.  (In
   * situations where the DBA has gone overboard on creating variant
   * indexes, this can make for a very large reduction in the number of
   * paths considered further.)
   *
   * We then sort the surviving paths with the cheapest-to-scan first, and
   * for each path, consider using that path alone as the basis for a bitmap
   * scan.  Then we consider bitmap AND scans formed from that path plus
   * each subsequent (higher-cost) path, adding on a subsequent path if it
   * results in a reduction in the estimated total scan cost. This means we
   * consider about O(N^2) rather than O(2^N) path combinations, which is
   * quite tolerable, especially given than N is usually reasonably small
   * because of the prefiltering step.  The cheapest of these is returned.
   *
   * We will only consider AND combinations in which no two indexes use the
   * same WHERE clause.  This is a bit of a kluge: it's needed because
   * costsize.c and clausesel.c aren't very smart about redundant clauses.
   * They will usually double-count the redundant clauses, producing a
   * too-small selectivity that makes a redundant AND step look like it
   * reduces the total cost.  Perhaps someday that code will be smarter and
   * we can remove this limitation.  (But note that this also defends
   * against flat-out duplicate input paths, which can happen because
   * match_join_clauses_to_index will find the same OR join clauses that
   * extract_restriction_or_clauses has pulled OR restriction clauses out
   * of.)
   *
   * For the same reason, we reject AND combinations in which an index
   * predicate clause duplicates another clause.  Here we find it necessary
   * to be even stricter: we'll reject a partial index if any of its
   * predicate clauses are implied by the set of WHERE clauses and predicate
   * clauses used so far.  This covers cases such as a condition "x = 42"
   * used with a plain index, followed by a clauseless scan of a partial
   * index "WHERE x >= 40 AND x < 50".  The partial index has been accepted
   * only because "x = 42" was present, and so allowing it would partially
   * double-count selectivity.  (We could use predicate_implied_by on
   * regular qual clauses too, to have a more intelligent, but much more
   * expensive, check for redundancy --- but in most cases simple equality
   * seems to suffice.)
   */

  /*
   * Extract clause usage info and detect any paths that use exactly the
   * same set of clauses; keep only the cheapest-to-scan of any such groups.
   * The surviving paths are put into an array for qsort'ing.
   */
  pathinfoarray = (PathClauseUsage **)
    palloc(npaths * sizeof(PathClauseUsage *));
  clauselist = NIL;
  npaths = 0;
  foreach(l, paths)
  {
    Path     *ipath = (Path *) lfirst(l);

    pathinfo = classify_index_clause_usage(ipath, &clauselist);

    /* If it's unclassifiable, treat it as distinct from all others */
    if (pathinfo->unclassifiable)
    {
      pathinfoarray[npaths++] = pathinfo;
      continue;
    }

    for (i = 0; 44i < npaths; i++26)
    {
      if (!pathinfoarray[i]->unclassifiable &&
        bms_equal(pathinfo->clauseids, pathinfoarray[i]->clauseids))
        break;
    }
    if (i < npaths)
    {
      /* duplicate clauseids, keep the cheaper one */
      Cost    ncost;
      Cost    ocost;
      Selectivity nselec;
      Selectivity oselec;

      cost_bitmap_tree_node(pathinfo->path, &ncost, &nselec);
      cost_bitmap_tree_node(pathinfoarray[i]->path, &ocost, &oselec);
      if (ncost < ocost)
        pathinfoarray[i] = pathinfo;
    }
    else
    {
      /* not duplicate clauseids, add to array */
      pathinfoarray[npaths++] = pathinfo;
    }
  }

  /* If only one surviving path, we're done */
  if (npaths == 1)
    return pathinfoarray[0]->path;

  /* Sort the surviving paths by index access cost */
  qsort(pathinfoarray, npaths, sizeof(PathClauseUsage *),
      path_usage_comparator);

  /*
   * For each surviving index, consider it as an "AND group leader", and see
   * whether adding on any of the later indexes results in an AND path with
   * cheaper total cost than before.  Then take the cheapest AND group.
   *
   * Note: paths that are either clauseless or unclassifiable will have
   * empty clauseids, so that they will not be rejected by the clauseids
   * filter here, nor will they cause later paths to be rejected by it.
   */
  for (i = 0; i < npaths; i++28)
  {
    Cost    costsofar;
    List     *qualsofar;
    Bitmapset  *clauseidsofar;
    ListCell   *lastcell;

    pathinfo = pathinfoarray[i];
    paths = list_make1(pathinfo->path);
    costsofar = bitmap_scan_cost_est(root, rel, pathinfo->path);
    qualsofar = list_concat(list_copy(pathinfo->quals),
                list_copy(pathinfo->preds));
    clauseidsofar = bms_copy(pathinfo->clauseids);
    lastcell = list_head(paths);  /* for quick deletions */

    for (j = i + 1; j < npaths; j++26)
    {
      Cost    newcost;

      pathinfo = pathinfoarray[j];
      /* Check for redundancy */
      if (bms_overlap(pathinfo->clauseids, clauseidsofar))
        continue;    /* consider it redundant */
      if (pathinfo->preds)
      {
        bool    redundant = false;

        /* we check each predicate clause separately */
        foreach(l, pathinfo->preds)
        {
          Node     *np = (Node *) lfirst(l);

          if (predicate_implied_by(list_make1(np), qualsofar, false))
          {
            redundant = true;
            break;  /* out of inner foreach loop */
          }
        }
        if (redundant)
          continue;
      }
      /* tentatively add new path to paths, so we can estimate cost */
      paths = lappend(paths, pathinfo->path);
      newcost = bitmap_and_cost_est(root, rel, paths);
      if (newcost < costsofar)
      {
        /* keep new path in paths, update subsidiary variables */
        costsofar = newcost;
        qualsofar = list_concat(qualsofar,
                    list_copy(pathinfo->quals));
        qualsofar = list_concat(qualsofar,
                    list_copy(pathinfo->preds));
        clauseidsofar = bms_add_members(clauseidsofar,
                        pathinfo->clauseids);
        lastcell = lnext(lastcell);
      }
      else
      {
        /* reject new path, remove it from paths list */
        paths = list_delete_cell(paths, lnext(lastcell), lastcell);
      }
      Assert(lnext(lastcell) == NULL);
    }

    /* Keep the cheapest AND-group (or singleton) */
    if (i == 0 || costsofar < bestcost17)
    {
      bestpaths = paths;
      bestcost = costsofar;
    }

    /* some easy cleanup (we don't try real hard though) */
    list_free(qualsofar);
  }

  if (list_length(bestpaths) == 1)
    return (Path *) linitial(bestpaths); /* no need for AND */
  return (Path *) create_bitmap_and_path(root, rel, bestpaths);
}

/* qsort comparator to sort in increasing index access cost order */
static int
path_usage_comparator(const void *a, const void *b)
{
  PathClauseUsage *pa = *(PathClauseUsage *const *) a;
  PathClauseUsage *pb = *(PathClauseUsage *const *) b;
  Cost    acost;
  Cost    bcost;
  Selectivity aselec;
  Selectivity bselec;

  cost_bitmap_tree_node(pa->path, &acost, &aselec);
  cost_bitmap_tree_node(pb->path, &bcost, &bselec);

  /*
   * If costs are the same, sort by selectivity.
   */
  if (acost < bcost)
    return -1;
  if (acost > bcost)
    return 1;

  if (aselec < bselec)
    return -1;
  if (aselec > bselec)
    return 1;

  return 0;
}

/*
 * Estimate the cost of actually executing a bitmap scan with a single
 * index path (which could be a BitmapAnd or BitmapOr node).
 */
static Cost
bitmap_scan_cost_est(PlannerInfo *root, RelOptInfo *rel, Path *ipath)
{
  BitmapHeapPath bpath;

  /* Set up a dummy BitmapHeapPath */
  bpath.path.type = T_BitmapHeapPath;
  bpath.path.pathtype = T_BitmapHeapScan;
  bpath.path.parent = rel;
  bpath.path.pathtarget = rel->reltarget;
  bpath.path.param_info = ipath->param_info;
  bpath.path.pathkeys = NIL;
  bpath.bitmapqual = ipath;

  /*
   * Check the cost of temporary path without considering parallelism.
   * Parallel bitmap heap path will be considered at later stage.
   */
  bpath.path.parallel_workers = 0;

  /* Now we can do cost_bitmap_heap_scan */
  cost_bitmap_heap_scan(&bpath.path, root, rel,
              bpath.path.param_info,
              ipath,
              get_loop_count(root, rel->relid,
                     PATH_REQ_OUTER(ipath)));

  return bpath.path.total_cost;
}

/*
 * Estimate the cost of actually executing a BitmapAnd scan with the given
 * inputs.
 */
static Cost
bitmap_and_cost_est(PlannerInfo *root, RelOptInfo *rel, List *paths)
{
  BitmapAndPath *apath;

  /*
   * Might as well build a real BitmapAndPath here, as the work is slightly
   * too complicated to be worth repeating just to save one palloc.
   */
  apath = create_bitmap_and_path(root, rel, paths);

  return bitmap_scan_cost_est(root, rel, (Path *) apath);
}


/*
 * classify_index_clause_usage
 *    Construct a PathClauseUsage struct describing the WHERE clauses and
 *    index predicate clauses used by the given indexscan path.
 *    We consider two clauses the same if they are equal().
 *
 * At some point we might want to migrate this info into the Path data
 * structure proper, but for the moment it's only needed within
 * choose_bitmap_and().
 *
 * *clauselist is used and expanded as needed to identify all the distinct
 * clauses seen across successive calls.  Caller must initialize it to NIL
 * before first call of a set.
 */
static PathClauseUsage *
classify_index_clause_usage(Path *path, List **clauselist)
{
  PathClauseUsage *result;
  Bitmapset  *clauseids;
  ListCell   *lc;

  result = (PathClauseUsage *) palloc(sizeof(PathClauseUsage));
  result->path = path;

  /* Recursively find the quals and preds used by the path */
  result->quals = NIL;
  result->preds = NIL;
  find_indexpath_quals(path, &result->quals, &result->preds);

  /*
   * Some machine-generated queries have outlandish numbers of qual clauses.
   * To avoid getting into O(N^2) behavior even in this preliminary
   * classification step, we want to limit the number of entries we can
   * accumulate in *clauselist.  Treat any path with more than 100 quals +
   * preds as unclassifiable, which will cause calling code to consider it
   * distinct from all other paths.
   */
  if (list_length(result->quals) + list_length(result->preds) > 100)
  {
    result->clauseids = NULL;
    result->unclassifiable = true;
    return result;
  }

  /* Build up a bitmapset representing the quals and preds */
  clauseids = NULL;
  foreach(lc, result->quals)
  {
    Node     *node = (Node *) lfirst(lc);

    clauseids = bms_add_member(clauseids,
                   find_list_position(node, clauselist));
  }
  foreach(lc, result->preds)
  {
    Node     *node = (Node *) lfirst(lc);

    clauseids = bms_add_member(clauseids,
                   find_list_position(node, clauselist));
  }
  result->clauseids = clauseids;
  result->unclassifiable = false;

  return result;
}


/*
 * find_indexpath_quals
 *
 * Given the Path structure for a plain or bitmap indexscan, extract lists
 * of all the indexquals and index predicate conditions used in the Path.
 * These are appended to the initial contents of *quals and *preds (hence
 * caller should initialize those to NIL).
 *
 * Note we are not trying to produce an accurate representation of the AND/OR
 * semantics of the Path, but just find out all the base conditions used.
 *
 * The result lists contain pointers to the expressions used in the Path,
 * but all the list cells are freshly built, so it's safe to destructively
 * modify the lists (eg, by concat'ing with other lists).
 */
static void
find_indexpath_quals(Path *bitmapqual, List **quals, List **preds)
{
  if (IsA(bitmapqual, BitmapAndPath))
  {
    BitmapAndPath *apath = (BitmapAndPath *) bitmapqual;
    ListCell   *l;

    foreach(l, apath->bitmapquals)
    {
      find_indexpath_quals((Path *) lfirst(l), quals, preds);
    }
  }
  else if (IsA(bitmapqual, BitmapOrPath))
  {
    BitmapOrPath *opath = (BitmapOrPath *) bitmapqual;
    ListCell   *l;

    foreach(l, opath->bitmapquals)
    {
      find_indexpath_quals((Path *) lfirst(l), quals, preds);
    }
  }
  else if (IsA(bitmapqual, IndexPath))
  {
    IndexPath  *ipath = (IndexPath *) bitmapqual;

    *quals = list_concat(*quals, get_actual_clauses(ipath->indexclauses));
    *preds = list_concat(*preds, list_copy(ipath->indexinfo->indpred));
  }
  else
    elog(ERROR, "unrecognized node type: %d", nodeTag(bitmapqual));
}


/*
 * find_list_position
 *    Return the given node's position (counting from 0) in the given
 *    list of nodes.  If it's not equal() to any existing list member,
 *    add it at the end, and return that position.
 */
static int
find_list_position(Node *node, List **nodelist)
{
  int     i;
  ListCell   *lc;

  i = 0;
  foreach(lc, *nodelist)
  {
    Node     *oldnode = (Node *) lfirst(lc);

    if (equal(node, oldnode))
      return i;
    i++;
  }

  *nodelist = lappend(*nodelist, node);

  return i;
}


/*
 * check_index_only
 *    Determine whether an index-only scan is possible for this index.
 */
static bool
check_index_only(RelOptInfo *rel, IndexOptInfo *index)
{
  bool    result;
  Bitmapset  *attrs_used = NULL;
  Bitmapset  *index_canreturn_attrs = NULL;
  Bitmapset  *index_cannotreturn_attrs = NULL;
  ListCell   *lc;
  int     i;

  /* Index-only scans must be enabled */
  if (!enable_indexonlyscan)
    return false;

  /*
   * Check that all needed attributes of the relation are available from the
   * index.
   */

  /*
   * First, identify all the attributes needed for joins or final output.
   * Note: we must look at rel's targetlist, not the attr_needed data,
   * because attr_needed isn't computed for inheritance child rels.
   */
  pull_varattnos((Node *) rel->reltarget->exprs, rel->relid, &attrs_used);

  /*
   * Add all the attributes used by restriction clauses; but consider only
   * those clauses not implied by the index predicate, since ones that are
   * so implied don't need to be checked explicitly in the plan.
   *
   * Note: attributes used only in index quals would not be needed at
   * runtime either, if we are certain that the index is not lossy.  However
   * it'd be complicated to account for that accurately, and it doesn't
   * matter in most cases, since we'd conclude that such attributes are
   * available from the index anyway.
   */
  foreach(lc, index->indrestrictinfo)
  {
    RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

    pull_varattnos((Node *) rinfo->clause, rel->relid, &attrs_used);
  }

  /*
   * Construct a bitmapset of columns that the index can return back in an
   * index-only scan.  If there are multiple index columns containing the
   * same attribute, all of them must be capable of returning the value,
   * since we might recheck operators on any of them.  (Potentially we could
   * be smarter about that, but it's such a weird situation that it doesn't
   * seem worth spending a lot of sweat on.)
   */
  for (i = 0; i < index->ncolumns; i++319k)
  {
    int     attno = index->indexkeys[i];

    /*
     * For the moment, we just ignore index expressions.  It might be nice
     * to do something with them, later.
     */
    if (attno == 0)
      continue;

    if (index->canreturn[i])
      index_canreturn_attrs =
        bms_add_member(index_canreturn_attrs,
                 attno - FirstLowInvalidHeapAttributeNumber);
    else
      index_cannotreturn_attrs =
        bms_add_member(index_cannotreturn_attrs,
                 attno - FirstLowInvalidHeapAttributeNumber);
  }

  index_canreturn_attrs = bms_del_members(index_canreturn_attrs,
                      index_cannotreturn_attrs);

  /* Do we have all the necessary attributes? */
  result = bms_is_subset(attrs_used, index_canreturn_attrs);

  bms_free(attrs_used);
  bms_free(index_canreturn_attrs);
  bms_free(index_cannotreturn_attrs);

  return result;
}

/*
 * get_loop_count
 *    Choose the loop count estimate to use for costing a parameterized path
 *    with the given set of outer relids.
 *
 * Since we produce parameterized paths before we've begun to generate join
 * relations, it's impossible to predict exactly how many times a parameterized
 * path will be iterated; we don't know the size of the relation that will be
 * on the outside of the nestloop.  However, we should try to account for
 * multiple iterations somehow in costing the path.  The heuristic embodied
 * here is to use the rowcount of the smallest other base relation needed in
 * the join clauses used by the path.  (We could alternatively consider the
 * largest one, but that seems too optimistic.)  This is of course the right
 * answer for single-other-relation cases, and it seems like a reasonable
 * zero-order approximation for multiway-join cases.
 *
 * In addition, we check to see if the other side of each join clause is on
 * the inside of some semijoin that the current relation is on the outside of.
 * If so, the only way that a parameterized path could be used is if the
 * semijoin RHS has been unique-ified, so we should use the number of unique
 * RHS rows rather than using the relation's raw rowcount.
 *
 * Note: for this to work, allpaths.c must establish all baserel size
 * estimates before it begins to compute paths, or at least before it
 * calls create_index_paths().
 */
static double
get_loop_count(PlannerInfo *root, Index cur_relid, Relids outer_relids)
{
  double    result;
  int     outer_relid;

  /* For a non-parameterized path, just return 1.0 quickly */
  if (outer_relids == NULL)
    return 1.0;

  result = 0.0;
  outer_relid = -1;
  while ((outer_relid = bms_next_member(outer_relids, outer_relid)) >= 0)
  {
    RelOptInfo *outer_rel;
    double    rowcount;

    /* Paranoia: ignore bogus relid indexes */
    if (outer_relid >= root->simple_rel_array_size)
      continue;
    outer_rel = root->simple_rel_array[outer_relid];
    if (outer_rel == NULL)
      continue;
    Assert(outer_rel->relid == outer_relid); /* sanity check on array */

    /* Other relation could be proven empty, if so ignore */
    if (IS_DUMMY_REL(outer_rel))
      continue;

    /* Otherwise, rel's rows estimate should be valid by now */
    Assert(outer_rel->rows > 0);

    /* Check to see if rel is on the inside of any semijoins */
    rowcount = adjust_rowcount_for_semijoins(root,
                         cur_relid,
                         outer_relid,
                         outer_rel->rows);

    /* Remember smallest row count estimate among the outer rels */
    if (result == 0.0 || result > rowcount32)
      result = rowcount;
  }
  /* Return 1.0 if we found no valid relations (shouldn't happen) */
  return (result > 0.0) ? result11.3k : 1.0229;
}

/*
 * Check to see if outer_relid is on the inside of any semijoin that cur_relid
 * is on the outside of.  If so, replace rowcount with the estimated number of
 * unique rows from the semijoin RHS (assuming that's smaller, which it might
 * not be).  The estimate is crude but it's the best we can do at this stage
 * of the proceedings.
 */
static double
adjust_rowcount_for_semijoins(PlannerInfo *root,
                Index cur_relid,
                Index outer_relid,
                double rowcount)
{
  ListCell   *lc;

  foreach(lc, root->join_info_list)
  {
    SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);

    if (sjinfo->jointype == JOIN_SEMI &&
      bms_is_member(cur_relid, sjinfo->syn_lefthand)105 &&
      bms_is_member(outer_relid, sjinfo->syn_righthand)3)
    {
      /* Estimate number of unique-ified rows */
      double    nraw;
      double    nunique;

      nraw = approximate_joinrel_size(root, sjinfo->syn_righthand);
      nunique = estimate_num_groups(root,
                      sjinfo->semi_rhs_exprs,
                      nraw,
                      NULL);
      if (rowcount > nunique)
        rowcount = nunique;
    }
  }
  return rowcount;
}

/*
 * Make an approximate estimate of the size of a joinrel.
 *
 * We don't have enough info at this point to get a good estimate, so we
 * just multiply the base relation sizes together.  Fortunately, this is
 * the right answer anyway for the most common case with a single relation
 * on the RHS of a semijoin.  Also, estimate_num_groups() has only a weak
 * dependency on its input_rows argument (it basically uses it as a clamp).
 * So we might be able to get a fairly decent end result even with a severe
 * overestimate of the RHS's raw size.
 */
static double
approximate_joinrel_size(PlannerInfo *root, Relids relids)
{
  double    rowcount = 1.0;
  int     relid;

  relid = -1;
  while ((relid = bms_next_member(relids, relid)) >= 0)
  {
    RelOptInfo *rel;

    /* Paranoia: ignore bogus relid indexes */
    if (relid >= root->simple_rel_array_size)
      continue;
    rel = root->simple_rel_array[relid];
    if (rel == NULL)
      continue;
    Assert(rel->relid == relid); /* sanity check on array */

    /* Relation could be proven empty, if so ignore */
    if (IS_DUMMY_REL(rel))
      continue;

    /* Otherwise, rel's rows estimate should be valid by now */
    Assert(rel->rows > 0);

    /* Accumulate product */
    rowcount *= rel->rows;
  }
  return rowcount;
}


/****************************************************************************
 *        ----  ROUTINES TO CHECK QUERY CLAUSES  ----
 ****************************************************************************/

/*
 * match_restriction_clauses_to_index
 *    Identify restriction clauses for the rel that match the index.
 *    Matching clauses are added to *clauseset.
 */
static void
match_restriction_clauses_to_index(RelOptInfo *rel, IndexOptInfo *index,
                   IndexClauseSet *clauseset)
{
  /* We can ignore clauses that are implied by the index predicate */
  match_clauses_to_index(index, index->indrestrictinfo, clauseset);
}

/*
 * match_join_clauses_to_index
 *    Identify join clauses for the rel that match the index.
 *    Matching clauses are added to *clauseset.
 *    Also, add any potentially usable join OR clauses to *joinorclauses.
 */
static void
match_join_clauses_to_index(PlannerInfo *root,
              RelOptInfo *rel, IndexOptInfo *index,
              IndexClauseSet *clauseset,
              List **joinorclauses)
{
  ListCell   *lc;

  /* Scan the rel's join clauses */
  foreach(lc, rel->joininfo)
  {
    RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

    /* Check if clause can be moved to this rel */
    if (!join_clause_is_movable_to(rinfo, rel))
      continue;

    /* Potentially usable, so see if it matches the index or is an OR */
    if (restriction_is_or_clause(rinfo))
      *joinorclauses = lappend(*joinorclauses, rinfo);
    else
      match_clause_to_index(index, rinfo, clauseset);
  }
}

/*
 * match_eclass_clauses_to_index
 *    Identify EquivalenceClass join clauses for the rel that match the index.
 *    Matching clauses are added to *clauseset.
 */
static void
match_eclass_clauses_to_index(PlannerInfo *root, IndexOptInfo *index,
                IndexClauseSet *clauseset)
{
  int     indexcol;

  /* No work if rel is not in any such ECs */
  if (!index->rel->has_eclass_joins)
    return;

  for (indexcol = 0; 16.9kindexcol < index->nkeycolumns; indexcol++22.7k)
  {
    ec_member_matches_arg arg;
    List     *clauses;

    /* Generate clauses, skipping any that join to lateral_referencers */
    arg.index = index;
    arg.indexcol = indexcol;
    clauses = generate_implied_equalities_for_column(root,
                             index->rel,
                             ec_member_matches_indexcol,
                             (void *) &arg,
                             index->rel->lateral_referencers);

    /*
     * We have to check whether the results actually do match the index,
     * since for non-btree indexes the EC's equality operators might not
     * be in the index opclass (cf ec_member_matches_indexcol).
     */
    match_clauses_to_index(index, clauses, clauseset);
  }
}

/*
 * match_clauses_to_index
 *    Perform match_clause_to_index() for each clause in a list.
 *    Matching clauses are added to *clauseset.
 */
static void
match_clauses_to_index(IndexOptInfo *index,
             List *clauses,
             IndexClauseSet *clauseset)
{
  ListCell   *lc;

  foreach(lc, clauses)
  {
    RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);

    match_clause_to_index(index, rinfo, clauseset);
  }
}

/*
 * match_clause_to_index
 *    Test whether a qual clause can be used with an index.
 *
 * If the clause is usable, add it to the appropriate list in *clauseset.
 * *clauseset must be initialized to zeroes before first call.
 *
 * Note: in some circumstances we may find the same RestrictInfos coming from
 * multiple places.  Defend against redundant outputs by refusing to add a
 * clause twice (pointer equality should be a good enough check for this).
 *
 * Note: it's possible that a badly-defined index could have multiple matching
 * columns.  We always select the first match if so; this avoids scenarios
 * wherein we get an inflated idea of the index's selectivity by using the
 * same clause multiple times with different index columns.
 */
static void
match_clause_to_index(IndexOptInfo *index,
            RestrictInfo *rinfo,
            IndexClauseSet *clauseset)
{
  int     indexcol;

  /*
   * Never match pseudoconstants to indexes.  (Normally a match could not
   * happen anyway, since a pseudoconstant clause couldn't contain a Var,
   * but what if someone builds an expression index on a constant? It's not
   * totally unreasonable to do so with a partial index, either.)
   */
  if (rinfo->pseudoconstant)
    return;

  /*
   * If clause can't be used as an indexqual because it must wait till after
   * some lower-security-level restriction clause, reject it.
   */
  if (!restriction_is_securely_promotable(rinfo, index->rel))
    return;

  /* OK, check each index key column for a match */
  for (indexcol = 0; 238kindexcol < index->nkeycolumns; indexcol++151k)
  {
    if (match_clause_to_indexcol(index,
                   indexcol,
                   rinfo))
    {
      clauseset->indexclauses[indexcol] =
        list_append_unique_ptr(clauseset->indexclauses[indexcol],
                     rinfo);
      clauseset->nonempty = true;
      return;
    }
  }
}

static bool is_yb_hash_code_call(Node *clause)
{
  return clause && IsA131k(clause, FuncExpr)
        && (((FuncExpr *) clause)->funcid == 154YB_HASH_CODE_OID154);
}

/*
 * match_clause_to_indexcol()
 *    Determines whether a restriction clause matches a column of an index.
 *
 *    To match an index normally, the clause:
 *
 *    (1)  must be in the form (indexkey op const) or (const op indexkey);
 *       and
 *    (2)  must contain an operator which is in the same family as the index
 *       operator for this column, or is a "special" operator as recognized
 *       by match_special_index_operator();
 *       and
 *    (3)  must match the collation of the index, if collation is relevant.
 *
 *    Our definition of "const" is exceedingly liberal: we allow anything that
 *    doesn't involve a volatile function or a Var of the index's relation.
 *    In particular, Vars belonging to other relations of the query are
 *    accepted here, since a clause of that form can be used in a
 *    parameterized indexscan.  It's the responsibility of higher code levels
 *    to manage restriction and join clauses appropriately.
 *
 *    Note: we do need to check for Vars of the index's relation on the
 *    "const" side of the clause, since clauses like (a.f1 OP (b.f2 OP a.f3))
 *    are not processable by a parameterized indexscan on a.f1, whereas
 *    something like (a.f1 OP (b.f2 OP c.f3)) is.
 *
 *    Presently, the executor can only deal with indexquals that have the
 *    indexkey on the left, so we can only use clauses that have the indexkey
 *    on the right if we can commute the clause to put the key on the left.
 *    We do not actually do the commuting here, but we check whether a
 *    suitable commutator operator is available.
 *
 *    If the index has a collation, the clause must have the same collation.
 *    For collation-less indexes, we assume it doesn't matter; this is
 *    necessary for cases like "hstore ? text", wherein hstore's operators
 *    don't care about collation but the clause will get marked with a
 *    collation anyway because of the text argument.  (This logic is
 *    embodied in the macro IndexCollMatchesExprColl.)
 *
 *    It is also possible to match RowCompareExpr clauses to indexes (but
 *    currently, only btree indexes handle this).  In this routine we will
 *    report a match if the first column of the row comparison matches the
 *    target index column.  This is sufficient to guarantee that some index
 *    condition can be constructed from the RowCompareExpr --- whether the
 *    remaining columns match the index too is considered in
 *    adjust_rowcompare_for_index().
 *
 *    It is also possible to match ScalarArrayOpExpr clauses to indexes, when
 *    the clause is of the form "indexkey op ANY (arrayconst)".
 *
 *    For boolean indexes, it is also possible to match the clause directly
 *    to the indexkey; or perhaps the clause is (NOT indexkey).
 *
 * 'index' is the index of interest.
 * 'indexcol' is a column number of 'index' (counting from 0).
 * 'rinfo' is the clause to be tested (as a RestrictInfo node).
 *
 * Returns true if the clause can be used with this index key.
 *
 * NOTE:  returns false if clause is an OR or AND clause; it is the
 * responsibility of higher-level routines to cope with those.
 */
static bool
match_clause_to_indexcol(IndexOptInfo *index,
             int indexcol,
             RestrictInfo *rinfo)
{
  Expr     *clause = rinfo->clause;
  Index   index_relid = index->rel->relid;
  Oid     opfamily;
  Oid     idxcollation;
  Node     *leftop,
         *rightop;
  Relids    left_relids;
  Relids    right_relids;
  Oid     expr_op;
  Oid     expr_coll;
  bool    plain_op;

  Assert(indexcol < index->nkeycolumns);

  opfamily = index->opfamily[indexcol];
  idxcollation = index->indexcollations[indexcol];

  /* First check for boolean-index cases. */
  if (IsBooleanOpfamily(opfamily))
  {
    if (match_boolean_index_clause((Node *) clause, indexcol, index))
      return true;
  }

  /*
   * Clause must be a binary opclause, or possibly a ScalarArrayOpExpr
   * (which is always binary, by definition).  Or it could be a
   * RowCompareExpr, which we pass off to match_rowcompare_to_indexcol().
   * Or, if the index supports it, we can handle IS NULL/NOT NULL clauses.
   */
  if (is_opclause(clause))
  {
    leftop = get_leftop(clause);
    rightop = get_rightop(clause);
    if (!leftop || !rightop)
      return false;
    left_relids = rinfo->left_relids;
    right_relids = rinfo->right_relids;
    expr_op = ((OpExpr *) clause)->opno;
    expr_coll = ((OpExpr *) clause)->inputcollid;
    plain_op = true;
  }
  else if (clause && IsA120k(clause, ScalarArrayOpExpr))
  {
    ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) clause;

    /* We only accept ANY clauses, not ALL */
    if (!saop->useOr)
      return false;
    leftop = (Node *) linitial(saop->args);
    rightop = (Node *) lsecond(saop->args);
    left_relids = NULL;   /* not actually needed */
    right_relids = pull_varnos(rightop);
    expr_op = saop->opno;
    expr_coll = saop->inputcollid;
    plain_op = false;
  }
  else if (clause && IsA8.12k(clause, RowCompareExpr))
  {
    return match_rowcompare_to_indexcol(index, indexcol,
                      opfamily, idxcollation,
                      (RowCompareExpr *) clause);
  }
  else if (index->amsearchnulls && IsA7.90k(clause, NullTest))
  {
    NullTest   *nt = (NullTest *) clause;

    if (!nt->argisrow &&
      match_index_to_operand((Node *) nt->arg, indexcol, index))
      return true;
    return false;
  }
  else
    return false;

  /*
   * Check for clauses of the form: (indexkey operator constant) or
   * (constant operator indexkey).  See above notes about const-ness.
   */
  if (match_index_to_operand(leftop, indexcol, index) &&
    !bms_is_member(index_relid, right_relids)130k &&
    !contain_volatile_functions(rightop)130k)
  {
    if (is_yb_hash_code_call(leftop)) {
        return is_indexable_operator(expr_op,
              INTEGER_LSM_FAM_OID, true)
            && is_opclause(clause);
    }

    if (IndexCollMatchesExprColl(idxcollation, expr_coll)
      && is_indexable_operator(expr_op, opfamily, true))
      return true;

    /*
     * If we didn't find a member of the index's opfamily, see whether it
     * is a "special" indexable operator.
     */
    if (plain_op &&
      match_special_index_operator(clause, opfamily,
                     idxcollation, true))
      return true;
    return false;
  }

  if (plain_op &&
    match_index_to_operand(rightop, indexcol, index)73.3k &&
    !bms_is_member(index_relid, left_relids)1.25k &&
    !contain_volatile_functions(leftop)1.25k)
  {
    if (is_yb_hash_code_call(rightop)) {
        return is_indexable_operator(expr_op,
              INTEGER_LSM_FAM_OID, true)
            && is_opclause(clause);
    }

    if (IndexCollMatchesExprColl(idxcollation, expr_coll) &&
      is_indexable_operator(expr_op, opfamily, false))
      return true;

    /*
     * If we didn't find a member of the index's opfamily, see whether it
     * is a "special" indexable operator.
     */
    if (match_special_index_operator(clause, opfamily,
                     idxcollation, false))
      return true;
    return false;
  }

  return false;
}

/*
 * is_indexable_operator
 *    Does the operator match the specified index opfamily?
 *
 * If the indexkey is on the right, what we actually want to know
 * is whether the operator has a commutator operator that matches
 * the opfamily.
 */
static bool
is_indexable_operator(Oid expr_op, Oid opfamily, bool indexkey_on_left)
{
  /* Get the commuted operator if necessary */
  if (!indexkey_on_left)
  {
    expr_op = get_commutator(expr_op);
    if (expr_op == InvalidOid)
      return false;
  }

  /* OK if the (commuted) operator is a member of the index's opfamily */
  return op_in_opfamily(expr_op, opfamily);
}

/*
 * match_rowcompare_to_indexcol()
 *    Handles the RowCompareExpr case for match_clause_to_indexcol(),
 *    which see for comments.
 */
static bool
match_rowcompare_to_indexcol(IndexOptInfo *index,
               int indexcol,
               Oid opfamily,
               Oid idxcollation,
               RowCompareExpr *clause)
{
  Index   index_relid = index->rel->relid;
  Node     *leftop,
         *rightop;
  Oid     expr_op;
  Oid     expr_coll;

  /* Forget it if we're not dealing with a btree or lsm index */
  if (index->relam != BTREE_AM_OID && index->relam != 197LSM_AM_OID197)
    return false;

  /*
   * We could do the matching on the basis of insisting that the opfamily
   * shown in the RowCompareExpr be the same as the index column's opfamily,
   * but that could fail in the presence of reverse-sort opfamilies: it'd be
   * a matter of chance whether RowCompareExpr had picked the forward or
   * reverse-sort family.  So look only at the operator, and match if it is
   * a member of the index's opfamily (after commutation, if the indexkey is
   * on the right).  We'll worry later about whether any additional
   * operators are matchable to the index.
   */
  leftop = (Node *) linitial(clause->largs);
  rightop = (Node *) linitial(clause->rargs);
  expr_op = linitial_oid(clause->opnos);
  expr_coll = linitial_oid(clause->inputcollids);

  /* Collations must match, if relevant */
  if (!IndexCollMatchesExprColl(idxcollation, expr_coll))
    return false;

  /*
   * These syntactic tests are the same as in match_clause_to_indexcol()
   */
  if (match_index_to_operand(leftop, indexcol, index) &&
    !bms_is_member(index_relid, pull_varnos(rightop))187 &&
    !contain_volatile_functions(rightop)187)
  {
    /* OK, indexkey is on left */
  }
  else if (match_index_to_operand(rightop, indexcol, index) &&
       !bms_is_member(index_relid, pull_varnos(leftop))0 &&
       !contain_volatile_functions(leftop)0)
  {
    /* indexkey is on right, so commute the operator */
    expr_op = get_commutator(expr_op);
    if (expr_op == InvalidOid)
      return false;
  }
  else
    return false;

  /* We're good if the operator is the right type of opfamily member */
  switch (get_op_opfamily_strategy(expr_op, opfamily))
  {
    case BTLessStrategyNumber:
    case BTLessEqualStrategyNumber:
    case BTGreaterEqualStrategyNumber:
    case BTGreaterStrategyNumber:
      return true;
  }

  return false;
}


/****************************************************************************
 *        ----  ROUTINES TO CHECK ORDERING OPERATORS  ----
 ****************************************************************************/

/*
 * match_pathkeys_to_index
 *    Test whether an index can produce output ordered according to the
 *    given pathkeys using "ordering operators".
 *
 * If it can, return a list of suitable ORDER BY expressions, each of the form
 * "indexedcol operator pseudoconstant", along with an integer list of the
 * index column numbers (zero based) that each clause would be used with.
 * NIL lists are returned if the ordering is not achievable this way.
 *
 * On success, the result list is ordered by pathkeys, and in fact is
 * one-to-one with the requested pathkeys.
 */
static void
match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
            List **orderby_clauses_p,
            List **clause_columns_p)
{
  List     *orderby_clauses = NIL;
  List     *clause_columns = NIL;
  ListCell   *lc1;

  *orderby_clauses_p = NIL; /* set default results */
  *clause_columns_p = NIL;

  /* Only indexes with the amcanorderbyop property are interesting here */
  if (!index->amcanorderbyop)
    return;

  foreach(lc1, pathkeys)
  {
    PathKey    *pathkey = (PathKey *) lfirst(lc1);
    bool    found = false;
    ListCell   *lc2;

    /*
     * Note: for any failure to match, we just return NIL immediately.
     * There is no value in matching just some of the pathkeys.
     */

    /* Pathkey must request default sort order for the target opfamily */
    if (pathkey->pk_strategy != BTLessStrategyNumber ||
      pathkey->pk_nulls_first)
      return;

    /* If eclass is volatile, no hope of using an indexscan */
    if (pathkey->pk_eclass->ec_has_volatile)
      return;

    /*
     * Try to match eclass member expression(s) to index.  Note that child
     * EC members are considered, but only when they belong to the target
     * relation.  (Unlike regular members, the same expression could be a
     * child member of more than one EC.  Therefore, the same index could
     * be considered to match more than one pathkey list, which is OK
     * here.  See also get_eclass_for_sort_expr.)
     */
    foreach(lc2, pathkey->pk_eclass->ec_members)
    {
      EquivalenceMember *member = (EquivalenceMember *) lfirst(lc2);
      int     indexcol;

      /* No possibility of match if it references other relations */
      if (!bms_equal(member->em_relids, index->rel->relids))
        continue;

      /*
       * We allow any column of the index to match each pathkey; they
       * don't have to match left-to-right as you might expect.  This is
       * correct for GiST, which is the sole existing AM supporting
       * amcanorderbyop.  We might need different logic in future for
       * other implementations.
       */
      for (indexcol = 0; 3indexcol < index->ncolumns; indexcol++3)
      {
        Expr     *expr;

        expr = match_clause_to_ordering_op(index,
                           indexcol,
                           member->em_expr,
                           pathkey->pk_opfamily);
        if (expr)
        {
          orderby_clauses = lappend(orderby_clauses, expr);
          clause_columns = lappend_int(clause_columns, indexcol);
          found = true;
          break;
        }
      }

      if (found)      /* don't want to look at remaining members */
        break;
    }

    if (!found)       /* fail if no match for this pathkey */
      return;
  }

  *orderby_clauses_p = orderby_clauses; /* success! */
  *clause_columns_p = clause_columns;
}

/*
 * match_clause_to_ordering_op
 *    Determines whether an ordering operator expression matches an
 *    index column.
 *
 *    This is similar to, but simpler than, match_clause_to_indexcol.
 *    We only care about simple OpExpr cases.  The input is a bare
 *    expression that is being ordered by, which must be of the form
 *    (indexkey op const) or (const op indexkey) where op is an ordering
 *    operator for the column's opfamily.
 *
 * 'index' is the index of interest.
 * 'indexcol' is a column number of 'index' (counting from 0).
 * 'clause' is the ordering expression to be tested.
 * 'pk_opfamily' is the btree opfamily describing the required sort order.
 *
 * Note that we currently do not consider the collation of the ordering
 * operator's result.  In practical cases the result type will be numeric
 * and thus have no collation, and it's not very clear what to match to
 * if it did have a collation.  The index's collation should match the
 * ordering operator's input collation, not its result.
 *
 * If successful, return 'clause' as-is if the indexkey is on the left,
 * otherwise a commuted copy of 'clause'.  If no match, return NULL.
 */
static Expr *
match_clause_to_ordering_op(IndexOptInfo *index,
              int indexcol,
              Expr *clause,
              Oid pk_opfamily)
{
  Oid     opfamily;
  Oid     idxcollation;
  Node     *leftop,
         *rightop;
  Oid     expr_op;
  Oid     expr_coll;
  Oid     sortfamily;
  bool    commuted;

  Assert(indexcol < index->nkeycolumns);

  opfamily = index->opfamily[indexcol];
  idxcollation = index->indexcollations[indexcol];

  /*
   * Clause must be a binary opclause.
   */
  if (!is_opclause(clause))
    return NULL;
  leftop = get_leftop(clause);
  rightop = get_rightop(clause);
  if (!leftop || !rightop)
    return NULL;
  expr_op = ((OpExpr *) clause)->opno;
  expr_coll = ((OpExpr *) clause)->inputcollid;

  /*
   * We can forget the whole thing right away if wrong collation.
   */
  if (!IndexCollMatchesExprColl(idxcollation, expr_coll))
    return NULL;

  /*
   * Check for clauses of the form: (indexkey operator constant) or
   * (constant operator indexkey).
   */
  if (match_index_to_operand(leftop, indexcol, index) &&
    !contain_var_clause(rightop) &&
    !contain_volatile_functions(rightop))
  {
    commuted = false;
  }
  else if (match_index_to_operand(rightop, indexcol, index) &&
       !contain_var_clause(leftop) &&
       !contain_volatile_functions(leftop))
  {
    /* Might match, but we need a commuted operator */
    expr_op = get_commutator(expr_op);
    if (expr_op == InvalidOid)
      return NULL;
    commuted = true;
  }
  else
    return NULL;

  /*
   * Is the (commuted) operator an ordering operator for the opfamily? And
   * if so, does it yield the right sorting semantics?
   */
  sortfamily = get_op_opfamily_sortfamily(expr_op, opfamily);
  if (sortfamily != pk_opfamily)
    return NULL;

  /* We have a match.  Return clause or a commuted version thereof. */
  if (commuted)
  {
    OpExpr     *newclause = makeNode(OpExpr);

    /* flat-copy all the fields of clause */
    memcpy(newclause, clause, sizeof(OpExpr));

    /* commute it */
    newclause->opno = expr_op;
    newclause->opfuncid = InvalidOid;
    newclause->args = list_make2(rightop, leftop);

    clause = (Expr *) newclause;
  }

  return clause;
}


/****************************************************************************
 *        ----  ROUTINES TO DO PARTIAL INDEX PREDICATE TESTS  ----
 ****************************************************************************/

/*
 * check_index_predicates
 *    Set the predicate-derived IndexOptInfo fields for each index
 *    of the specified relation.
 *
 * predOK is set true if the index is partial and its predicate is satisfied
 * for this query, ie the query's WHERE clauses imply the predicate.
 *
 * indrestrictinfo is set to the relation's baserestrictinfo list less any
 * conditions that are implied by the index's predicate.  (Obviously, for a
 * non-partial index, this is the same as baserestrictinfo.)  Such conditions
 * can be dropped from the plan when using the index, in certain cases.
 *
 * At one time it was possible for this to get re-run after adding more
 * restrictions to the rel, thus possibly letting us prove more indexes OK.
 * That doesn't happen any more (at least not in the core code's usage),
 * but this code still supports it in case extensions want to mess with the
 * baserestrictinfo list.  We assume that adding more restrictions can't make
 * an index not predOK.  We must recompute indrestrictinfo each time, though,
 * to make sure any newly-added restrictions get into it if needed.
 */
void
check_index_predicates(PlannerInfo *root, RelOptInfo *rel)
{
  List     *clauselist;
  bool    have_partial;
  bool    is_target_rel;
  Relids    otherrels;
  ListCell   *lc;

  /* Indexes are available only on base or "other" member relations. */
  Assert(IS_SIMPLE_REL(rel));

  /*
   * Initialize the indrestrictinfo lists to be identical to
   * baserestrictinfo, and check whether there are any partial indexes.  If
   * not, this is all we need to do.
   */
  have_partial = false;
  foreach(lc, rel->indexlist)
  {
    IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);

    index->indrestrictinfo = rel->baserestrictinfo;
    if (index->indpred)
      have_partial = true;
  }
  if (!have_partial)
    return;

  /*
   * Construct a list of clauses that we can assume true for the purpose of
   * proving the index(es) usable.  Restriction clauses for the rel are
   * always usable, and so are any join clauses that are "movable to" this
   * rel.  Also, we can consider any EC-derivable join clauses (which must
   * be "movable to" this rel, by definition).
   */
  clauselist = list_copy(rel->baserestrictinfo);

  /* Scan the rel's join clauses */
  foreach(lc, rel->joininfo)
  {
    RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

    /* Check if clause can be moved to this rel */
    if (!join_clause_is_movable_to(rinfo, rel))
      continue;

    clauselist = lappend(clauselist, rinfo);
  }

  /*
   * Add on any equivalence-derivable join clauses.  Computing the correct
   * relid sets for generate_join_implied_equalities is slightly tricky
   * because the rel could be a child rel rather than a true baserel, and in
   * that case we must remove its parents' relid(s) from all_baserels.
   */
  if (rel->reloptkind == RELOPT_OTHER_MEMBER_REL)
    otherrels = bms_difference(root->all_baserels,
                   find_childrel_parents(root, rel));
  else
    otherrels = bms_difference(root->all_baserels, rel->relids);

  if (!bms_is_empty(otherrels))
    clauselist =
      list_concat(clauselist,
            generate_join_implied_equalities(root,
                             bms_union(rel->relids,
                                   otherrels),
                             otherrels,
                             rel));

  /*
   * Normally we remove quals that are implied by a partial index's
   * predicate from indrestrictinfo, indicating that they need not be
   * checked explicitly by an indexscan plan using this index.  However, if
   * the rel is a target relation of UPDATE/DELETE/SELECT FOR UPDATE, we
   * cannot remove such quals from the plan, because they need to be in the
   * plan so that they will be properly rechecked by EvalPlanQual testing.
   * Some day we might want to remove such quals from the main plan anyway
   * and pass them through to EvalPlanQual via a side channel; but for now,
   * we just don't remove implied quals at all for target relations.
   */
  is_target_rel = (rel->relid == root->parse->resultRelation ||
           get_plan_rowmark(root->rowMarks, rel->relid) != NULL175);

  /*
   * Now try to prove each index predicate true, and compute the
   * indrestrictinfo lists for partial indexes.  Note that we compute the
   * indrestrictinfo list even for non-predOK indexes; this might seem
   * wasteful, but we may be able to use such indexes in OR clauses, cf
   * generate_bitmap_or_paths().
   */
  foreach(lc, rel->indexlist)
  {
    IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);
    ListCell   *lcr;

    if (index->indpred == NIL)
      continue;      /* ignore non-partial indexes here */

    if (!index->predOK)   /* don't repeat work if already proven OK */
      index->predOK = predicate_implied_by(index->indpred, clauselist,
                         false);

    /* If rel is an update target, leave indrestrictinfo as set above */
    if (is_target_rel)
      continue;

    /* Else compute indrestrictinfo as the non-implied quals */
    index->indrestrictinfo = NIL;
    foreach(lcr, rel->baserestrictinfo)
    {
      RestrictInfo *rinfo = (RestrictInfo *) lfirst(lcr);

      /* predicate_implied_by() assumes first arg is immutable */
      if (contain_mutable_functions((Node *) rinfo->clause) ||
        !predicate_implied_by(list_make1(rinfo->clause),
                    index->indpred, false))
        index->indrestrictinfo = lappend(index->indrestrictinfo, rinfo);
    }
  }
}

/****************************************************************************
 *        ----  ROUTINES TO CHECK EXTERNALLY-VISIBLE CONDITIONS  ----
 ****************************************************************************/

/*
 * ec_member_matches_indexcol
 *    Test whether an EquivalenceClass member matches an index column.
 *
 * This is a callback for use by generate_implied_equalities_for_column.
 */
static bool
ec_member_matches_indexcol(PlannerInfo *root, RelOptInfo *rel,
               EquivalenceClass *ec, EquivalenceMember *em,
               void *arg)
{
  IndexOptInfo *index = ((ec_member_matches_arg *) arg)->index;
  int     indexcol = ((ec_member_matches_arg *) arg)->indexcol;
  Oid     curFamily;
  Oid     curCollation;

  Assert(indexcol < index->nkeycolumns);

  curFamily = index->opfamily[indexcol];
  curCollation = index->indexcollations[indexcol];

  /*
   * If it's a btree or lsm index, we can reject it if its opfamily isn't
   * compatible with the EC, since no clause generated from the EC could be
   * used with the index.  For non-btree indexes, we can't easily tell
   * whether clauses generated from the EC could be used with the index, so
   * don't check the opfamily.  This might mean we return "true" for a
   * useless EC, so we have to recheck the results of
   * generate_implied_equalities_for_column; see
   * match_eclass_clauses_to_index.
   */
  if ((index->relam == BTREE_AM_OID || index->relam == 20.8kLSM_AM_OID20.8k) &&
    !list_member_oid(ec->ec_opfamilies, curFamily))
    return false;

  /* We insist on collation match for all index types, though */
  if (!IndexCollMatchesExprColl(curCollation, ec->ec_collation))
    return false;

  return match_index_to_operand((Node *) em->em_expr, indexcol, index);
}

/*
 * relation_has_unique_index_for
 *    Determine whether the relation provably has at most one row satisfying
 *    a set of equality conditions, because the conditions constrain all
 *    columns of some unique index.
 *
 * The conditions can be represented in either or both of two ways:
 * 1. A list of RestrictInfo nodes, where the caller has already determined
 * that each condition is a mergejoinable equality with an expression in
 * this relation on one side, and an expression not involving this relation
 * on the other.  The transient outer_is_left flag is used to identify which
 * side we should look at: left side if outer_is_left is false, right side
 * if it is true.
 * 2. A list of expressions in this relation, and a corresponding list of
 * equality operators. The caller must have already checked that the operators
 * represent equality.  (Note: the operators could be cross-type; the
 * expressions should correspond to their RHS inputs.)
 *
 * The caller need only supply equality conditions arising from joins;
 * this routine automatically adds in any usable baserestrictinfo clauses.
 * (Note that the passed-in restrictlist will be destructively modified!)
 */
bool
relation_has_unique_index_for(PlannerInfo *root, RelOptInfo *rel,
                List *restrictlist,
                List *exprlist, List *oprlist)
{
  ListCell   *ic;

  Assert(list_length(exprlist) == list_length(oprlist));

  /* Short-circuit if no indexes... */
  if (rel->indexlist == NIL)
    return false;

  /*
   * Examine the rel's restriction clauses for usable var = const clauses
   * that we can add to the restrictlist.
   */
  foreach(ic, rel->baserestrictinfo)
  {
    RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(ic);

    /*
     * Note: can_join won't be set for a restriction clause, but
     * mergeopfamilies will be if it has a mergejoinable operator and
     * doesn't contain volatile functions.
     */
    if (restrictinfo->mergeopfamilies == NIL)
      continue;      /* not mergejoinable */

    /*
     * The clause certainly doesn't refer to anything but the given rel.
     * If either side is pseudoconstant then we can use it.
     */
    if (bms_is_empty(restrictinfo->left_relids))
    {
      /* righthand side is inner */
      restrictinfo->outer_is_left = true;
    }
    else if (bms_is_empty(restrictinfo->right_relids))
    {
      /* lefthand side is inner */
      restrictinfo->outer_is_left = false;
    }
    else
      continue;

    /* OK, add to list */
    restrictlist = lappend(restrictlist, restrictinfo);
  }

  /* Short-circuit the easy case */
  if (restrictlist == NIL && exprlist == 54NIL54)
    return false;

  /* Examine each index of the relation ... */
  foreach(ic, rel->indexlist)
  {
    IndexOptInfo *ind = (IndexOptInfo *) lfirst(ic);
    int     c;

    /*
     * If the index is not unique, or not immediately enforced, or if it's
     * a partial index that doesn't match the query, it's useless here.
     */
    if (!ind->unique || !ind->immediate21.2k ||
      (21.2kind->indpred != 21.2kNIL21.2k && !ind->predOK0))
      continue;

    /*
     * Try to find each index column in the lists of conditions.  This is
     * O(N^2) or worse, but we expect all the lists to be short.
     */
    for (c = 0; 21.2kc < ind->ncolumns; c++18.8k)
    {
      bool    matched = false;
      ListCell   *lc;
      ListCell   *lc2;

      foreach(lc, restrictlist)
      {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
        Node     *rexpr;

        /*
         * The condition's equality operator must be a member of the
         * index opfamily, else it is not asserting the right kind of
         * equality behavior for this index.  We check this first
         * since it's probably cheaper than match_index_to_operand().
         */
        if (!list_member_oid(rinfo->mergeopfamilies, ind->opfamily[c]))
          continue;

        /*
         * XXX at some point we may need to check collations here too.
         * For the moment we assume all collations reduce to the same
         * notion of equality.
         */

        /* OK, see if the condition operand matches the index key */
        if (rinfo->outer_is_left)
          rexpr = get_rightop(rinfo->clause);
        else
          rexpr = get_leftop(rinfo->clause);

        if (match_index_to_operand(rexpr, c, ind))
        {
          matched = true; /* column is unique */
          break;
        }
      }

      if (matched)
        continue;

      forboth(lc, exprlist, lc2, oprlist)
      {
        Node     *expr = (Node *) lfirst(lc);
        Oid     opr = lfirst_oid(lc2);

        /* See if the expression matches the index key */
        if (!match_index_to_operand(expr, c, ind))
          continue;

        /*
         * The equality operator must be a member of the index
         * opfamily, else it is not asserting the right kind of
         * equality behavior for this index.  We assume the caller
         * determined it is an equality operator, so we don't need to
         * check any more tightly than this.
         */
        if (!op_in_opfamily(opr, ind->opfamily[c]))
          continue;

        /*
         * XXX at some point we may need to check collations here too.
         * For the moment we assume all collations reduce to the same
         * notion of equality.
         */

        matched = true; /* column is unique */
        break;
      }

      if (!matched)
        break;     /* no match; this index doesn't help us */
    }

    /* Matched all columns of this index? */
    if (c == ind->ncolumns)
      return true;
  }

  return false;
}

/*
 * indexcol_is_bool_constant_for_query
 *
 * If an index column is constrained to have a constant value by the query's
 * WHERE conditions, then it's irrelevant for sort-order considerations.
 * Usually that means we have a restriction clause WHERE indexcol = constant,
 * which gets turned into an EquivalenceClass containing a constant, which
 * is recognized as redundant by build_index_pathkeys().  But if the index
 * column is a boolean variable (or expression), then we are not going to
 * see WHERE indexcol = constant, because expression preprocessing will have
 * simplified that to "WHERE indexcol" or "WHERE NOT indexcol".  So we are not
 * going to have a matching EquivalenceClass (unless the query also contains
 * "ORDER BY indexcol").  To allow such cases to work the same as they would
 * for non-boolean values, this function is provided to detect whether the
 * specified index column matches a boolean restriction clause.
 */
bool
indexcol_is_bool_constant_for_query(IndexOptInfo *index, int indexcol)
{
  ListCell   *lc;

  /* If the index isn't boolean, we can't possibly get a match */
  if (!IsBooleanOpfamily(index->opfamily[indexcol]))
    return false;

  /* Check each restriction clause for the index's rel */
  foreach(lc, index->rel->baserestrictinfo)
  {
    RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

    /*
     * As in match_clause_to_indexcol, never match pseudoconstants to
     * indexes.  (It might be semantically okay to do so here, but the
     * odds of getting a match are negligible, so don't waste the cycles.)
     */
    if (rinfo->pseudoconstant)
      continue;

    /* See if we can match the clause's expression to the index column */
    if (match_boolean_index_clause((Node *) rinfo->clause, indexcol, index))
      return true;
  }

  return false;
}


/****************************************************************************
 *        ----  ROUTINES TO CHECK OPERANDS  ----
 ****************************************************************************/

/*
 * match_index_to_operand()
 *    Generalized test for a match between an index's key
 *    and the operand on one side of a restriction or join clause.
 *
 * operand: the nodetree to be compared to the index
 * indexcol: the column number of the index (counting from 0)
 * index: the index of interest
 *
 * Note that we aren't interested in collations here; the caller must check
 * for a collation match, if it's dealing with an operator where that matters.
 *
 * This is exported for use in selfuncs.c.
 */
bool
match_index_to_operand(Node *operand,
             int indexcol,
             IndexOptInfo *index)
{
  int     indkey;

  /*
   * Ignore any RelabelType node above the operand.   This is needed to be
   * able to apply indexscanning in binary-compatible-operator cases. Note:
   * we can assume there is at most one RelabelType node;
   * eval_const_expressions() will have simplified if more than one.
   */
  if (operand518k && IsA(operand, RelabelType))
    operand = (Node *) ((RelabelType *) operand)->arg;

  indkey = index->indexkeys[indexcol];
  if (indkey != 0)
  {

    if (operand518k && IsA(operand, FuncExpr))
    {
      /*
       * YB: Forming an estimate to see if this call can be pushed down
       * by assessing whether or not its parameters are all column
       * variables and whether or not the number of arguments to the call
       * is the same as the number of hash columns in the primary key
       * of the index in question
       */
      FuncExpr *fn = (FuncExpr *) operand;
      if (fn->funcid == YB_HASH_CODE_OID
        && fn->args->length > 0963
        && index->nhashcolumns == fn->args->length963)
      {
        Relation indrel = RelationIdGetRelation(index->indexoid);
        Bitmapset *hash_keys = NULL;
        for (int natt = 1;
            natt <= indrel->rd_index->indnkeyatts; natt++2.13k)
        {
          if (indrel->rd_indoption[natt - 1] & INDOPTION_HASH)
          {
            int table_att = index->indexkeys[natt - 1];
            hash_keys = bms_add_member(hash_keys,
                    YBAttnumToBmsIndex(indrel, table_att));
          }
        }
        ListCell *ls;
        bool can_pushdown_hash_call = true;
        Bitmapset *args_bms = NULL;
        int last_index_att = -1;
        foreach(ls, fn->args)
        {
          Expr *arg = (Expr *) lfirst(ls);
          if (!IsA(arg, Var))
          {
            can_pushdown_hash_call = false;
            break;
          }

          Var *var = (Var *) arg;

          if (index->rel->relid != var->varno)
          {
            can_pushdown_hash_call = false;
            break;
          }

          /* YB: Need to make sure that the arguments to
           * yb_hash_code are in the correct order
           * we can make this for loop to map from index att
           * to table att slightly more efficient by starting the
           * loop from last_index_att */
          int index_att = -1;
          for (int natt = 1;
            natt <= indrel->rd_index->indnkeyatts; natt++2.17k)
          {
            int cand_table_att = index->indexkeys[natt - 1];
            if (cand_table_att == var->varattno)
            {
              index_att = natt;
              break;
            }
          }

          if (index_att <= last_index_att) {
            can_pushdown_hash_call = false;
            break;
          } else {
            last_index_att = index_att;
          }

          int arg_bms_index = YBAttnumToBmsIndex(indrel,
                              var->varattno);
          args_bms = bms_add_member(args_bms, arg_bms_index);
        }
        can_pushdown_hash_call &= bms_equal(args_bms, hash_keys);

        RelationClose(indrel);
        bms_free(args_bms);
        bms_free(hash_keys);
        return can_pushdown_hash_call;
      }
    }
    /*
     * Simple index column; operand must be a matching Var.
     */
    if (517koperand517k && IsA(operand, Var) &&
      index->rel->relid == ((Var *) operand)->varno449k &&
      indkey == ((Var *) operand)->varattno441k)
      return true;
  }
  else
  {
    /*
     * Index expression; find the correct expression.  (This search could
     * be avoided, at the cost of complicating all the callers of this
     * routine; doesn't seem worth it.)
     */
    ListCell   *indexpr_item;
    int     i;
    Node     *indexkey;

    indexpr_item = list_head(index->indexprs);
    for (i = 0; i < indexcol; i++48)
    {
      if (index->indexkeys[i] == 0)
      {
        if (indexpr_item == NULL)
          elog(ERROR, "wrong number of index expressions");
        indexpr_item = lnext(indexpr_item);
      }
    }
    if (indexpr_item == NULL)
      elog(ERROR, "wrong number of index expressions");
    indexkey = (Node *) lfirst(indexpr_item);

    /*
     * Does it match the operand?  Again, strip any relabeling.
     */
    if (indexkey && IsA419(indexkey, RelabelType))
      indexkey = (Node *) ((RelabelType *) indexkey)->arg;

    if (equal(indexkey, operand))
      return true;
  }

  return false;
}

/****************************************************************************
 *      ----  ROUTINES FOR "SPECIAL" INDEXABLE OPERATORS  ----
 ****************************************************************************/

/*
 * These routines handle special optimization of operators that can be
 * used with index scans even though they are not known to the executor's
 * indexscan machinery.  The key idea is that these operators allow us
 * to derive approximate indexscan qual clauses, such that any tuples
 * that pass the operator clause itself must also satisfy the simpler
 * indexscan condition(s).  Then we can use the indexscan machinery
 * to avoid scanning as much of the table as we'd otherwise have to,
 * while applying the original operator as a qpqual condition to ensure
 * we deliver only the tuples we want.  (In essence, we're using a regular
 * index as if it were a lossy index.)
 *
 * An example of what we're doing is
 *      textfield LIKE 'abc%'
 * from which we can generate the indexscanable conditions
 *      textfield >= 'abc' AND textfield < 'abd'
 * which allow efficient scanning of an index on textfield.
 * (In reality, character set and collation issues make the transformation
 * from LIKE to indexscan limits rather harder than one might think ...
 * but that's the basic idea.)
 *
 * Another thing that we do with this machinery is to provide special
 * smarts for "boolean" indexes (that is, indexes on boolean columns
 * that support boolean equality).  We can transform a plain reference
 * to the indexkey into "indexkey = true", or "NOT indexkey" into
 * "indexkey = false", so as to make the expression indexable using the
 * regular index operators.  (As of Postgres 8.1, we must do this here
 * because constant simplification does the reverse transformation;
 * without this code there'd be no way to use such an index at all.)
 *
 * Three routines are provided here:
 *
 * match_special_index_operator() is just an auxiliary function for
 * match_clause_to_indexcol(); after the latter fails to recognize a
 * restriction opclause's operator as a member of an index's opfamily,
 * it asks match_special_index_operator() whether the clause should be
 * considered an indexqual anyway.
 *
 * match_boolean_index_clause() similarly detects clauses that can be
 * converted into boolean equality operators.
 *
 * expand_indexqual_conditions() converts a list of RestrictInfo nodes
 * (with implicit AND semantics across list elements) into a list of clauses
 * that the executor can actually handle.  For operators that are members of
 * the index's opfamily this transformation is a no-op, but clauses recognized
 * by match_special_index_operator() or match_boolean_index_clause() must be
 * converted into one or more "regular" indexqual conditions.
 */

/*
 * match_boolean_index_clause
 *    Recognize restriction clauses that can be matched to a boolean index.
 *
 * This should be called only when IsBooleanOpfamily() recognizes the
 * index's operator family.  We check to see if the clause matches the
 * index's key.
 */
static bool
match_boolean_index_clause(Node *clause,
               int indexcol,
               IndexOptInfo *index)
{
  /* Direct match? */
  if (match_index_to_operand(clause, indexcol, index))
    return true;
  /* NOT clause? */
  if (not_clause(clause))
  {
    if (match_index_to_operand((Node *) get_notclausearg((Expr *) clause),
                   indexcol, index))
      return true;
  }

  /*
   * Since we only consider clauses at top level of WHERE, we can convert
   * indexkey IS TRUE and indexkey IS FALSE to index searches as well. The
   * different meaning for NULL isn't important.
   */
  else if (clause && IsA(clause, BooleanTest))
  {
    BooleanTest *btest = (BooleanTest *) clause;

    if (btest->booltesttype == IS_TRUE ||
      btest->booltesttype == IS_FALSE)
      if (match_index_to_operand((Node *) btest->arg,
                     indexcol, index))
        return true;
  }
  return false;
}

/*
 * match_special_index_operator
 *    Recognize restriction clauses that can be used to generate
 *    additional indexscanable qualifications.
 *
 * The given clause is already known to be a binary opclause having
 * the form (indexkey OP pseudoconst) or (pseudoconst OP indexkey),
 * but the OP proved not to be one of the index's opfamily operators.
 * Return 'true' if we can do something with it anyway.
 */
static bool
match_special_index_operator(Expr *clause, Oid opfamily, Oid idxcollation,
               bool indexkey_on_left)
{
  bool    isIndexable = false;
  Node     *rightop;
  Oid     expr_op;
  Oid     expr_coll;
  Const    *patt;
  Const    *prefix = NULL;
  Pattern_Prefix_Status pstatus = Pattern_Prefix_None;

  /*
   * Currently, all known special operators require the indexkey on the
   * left, but this test could be pushed into the switch statement if some
   * are added that do not...
   */
  if (!indexkey_on_left)
    return false;

  /* we know these will succeed */
  rightop = get_rightop(clause);
  expr_op = ((OpExpr *) clause)->opno;
  expr_coll = ((OpExpr *) clause)->inputcollid;

  /* again, required for all current special ops: */
  if (!IsA(rightop, Const) ||
    ((Const *) rightop)->constisnull14.1k)
    return false;
  patt = (Const *) rightop;

  switch (expr_op)
  {
    case OID_TEXT_LIKE_OP:
    case OID_BPCHAR_LIKE_OP:
    case OID_NAME_LIKE_OP:
      /* the right-hand const is type text for all of these */
      pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like, expr_coll,
                       &prefix, NULL);
      isIndexable = (pstatus != Pattern_Prefix_None);
      break;

    case OID_BYTEA_LIKE_OP:
      pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like, expr_coll,
                       &prefix, NULL);
      isIndexable = (pstatus != Pattern_Prefix_None);
      break;

    case OID_TEXT_ICLIKE_OP:
    case OID_BPCHAR_ICLIKE_OP:
    case OID_NAME_ICLIKE_OP:
      /* the right-hand const is type text for all of these */
      pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like_IC, expr_coll,
                       &prefix, NULL);
      isIndexable = (pstatus != Pattern_Prefix_None);
      break;

    case OID_TEXT_REGEXEQ_OP:
    case OID_BPCHAR_REGEXEQ_OP:
    case OID_NAME_REGEXEQ_OP:
      /* the right-hand const is type text for all of these */
      pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex, expr_coll,
                       &prefix, NULL);
      isIndexable = (pstatus != Pattern_Prefix_None);
      break;

    case OID_TEXT_ICREGEXEQ_OP:
    case OID_BPCHAR_ICREGEXEQ_OP:
    case OID_NAME_ICREGEXEQ_OP:
      /* the right-hand const is type text for all of these */
      pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex_IC, expr_coll,
                       &prefix, NULL);
      isIndexable = (pstatus != Pattern_Prefix_None);
      break;

    case OID_INET_SUB_OP:
    case OID_INET_SUBEQ_OP:
      isIndexable = true;
      break;
  }

  if (prefix)
  {
    pfree(DatumGetPointer(prefix->constvalue));
    pfree(prefix);
  }

  /* done if the expression doesn't look indexable */
  if (!isIndexable)
    return false;

  /*
   * Must also check that index's opfamily supports the operators we will
   * want to apply.  (A hash index, for example, will not support ">=".)
   * Currently, only btree, lsm and spgist support the operators we need.
   *
   * Note: actually, in the Pattern_Prefix_Exact case, we only need "=" so a
   * hash index would work.  Currently it doesn't seem worth checking for
   * that, however.
   *
   * We insist on the opfamily being the specific one we expect, else we'd
   * do the wrong thing if someone were to make a reverse-sort opfamily with
   * the same operators.
   *
   * The non-pattern opclasses will not sort the way we need in most non-C
   * locales.  We can use such an index anyway for an exact match (simple
   * equality), but not for prefix-match cases.  Note that here we are
   * looking at the index's collation, not the expression's collation --
   * this test is *not* dependent on the LIKE/regex operator's collation.
   */
  switch (expr_op)
  {
    case OID_TEXT_LIKE_OP:
    case OID_TEXT_ICLIKE_OP:
    case OID_TEXT_REGEXEQ_OP:
    case OID_TEXT_ICREGEXEQ_OP:
      isIndexable =
        (opfamily == TEXT_PATTERN_BTREE_FAM_OID) ||
        (opfamily == TEXT_PATTERN_LSM_FAM_OID) ||
        (opfamily == TEXT_SPGIST_FAM_OID) ||
        ((opfamily == TEXT_BTREE_FAM_OID ||
          opfamily == TEXT_LSM_FAM_OID) &&
         (pstatus == Pattern_Prefix_Exact ||
          lc_collate_is_c(idxcollation)0));
      break;

    case OID_BPCHAR_LIKE_OP:
    case OID_BPCHAR_ICLIKE_OP:
    case OID_BPCHAR_REGEXEQ_OP:
    case OID_BPCHAR_ICREGEXEQ_OP:
      isIndexable =
        (opfamily == BPCHAR_PATTERN_BTREE_FAM_OID) ||
        (opfamily == BPCHAR_PATTERN_LSM_FAM_OID) ||
        ((opfamily == BPCHAR_BTREE_FAM_OID ||
          opfamily == BPCHAR_LSM_FAM_OID) &&
         (pstatus == Pattern_Prefix_Exact ||
          lc_collate_is_c(idxcollation)));
      break;

    case OID_NAME_LIKE_OP:
    case OID_NAME_ICLIKE_OP:
    case OID_NAME_REGEXEQ_OP:
    case OID_NAME_ICREGEXEQ_OP:
      /* name uses locale-insensitive sorting */
      isIndexable = (opfamily == NAME_BTREE_FAM_OID || opfamily == NAME_LSM_FAM_OID);
      break;

    case OID_BYTEA_LIKE_OP:
      isIndexable = (opfamily == BYTEA_BTREE_FAM_OID || opfamily == BYTEA_LSM_FAM_OID);
      break;

    case OID_INET_SUB_OP:
    case OID_INET_SUBEQ_OP:
      isIndexable = (opfamily == NETWORK_BTREE_FAM_OID || opfamily == NETWORK_LSM_FAM_OID);
      break;
  }

  return isIndexable;
}

/*
 * expand_indexqual_conditions
 *    Given a list of RestrictInfo nodes, produce a list of directly usable
 *    index qual clauses.
 *
 * Standard qual clauses (those in the index's opfamily) are passed through
 * unchanged.  Boolean clauses and "special" index operators are expanded
 * into clauses that the indexscan machinery will know what to do with.
 * RowCompare clauses are simplified if necessary to create a clause that is
 * fully checkable by the index.
 *
 * In addition to the expressions themselves, there are auxiliary lists
 * of the index column numbers that the clauses are meant to be used with;
 * we generate an updated column number list for the result.  (This is not
 * the identical list because one input clause sometimes produces more than
 * one output clause.)
 *
 * The input clauses are sorted by column number, and so the output is too.
 * (This is depended on in various places in both planner and executor.)
 */
void
expand_indexqual_conditions(IndexOptInfo *index,
              List *indexclauses, List *indexclausecols,
              List **indexquals_p, List **indexqualcols_p)
{
  List     *indexquals = NIL;
  List     *indexqualcols = NIL;
  ListCell   *lcc,
         *lci;

  forboth(lcc, indexclauses, lci, indexclausecols)
  {
    RestrictInfo *rinfo = (RestrictInfo *) lfirst(lcc);
    int     indexcol = lfirst_int(lci);
    Expr     *clause = rinfo->clause;
    Oid     curFamily;
    Oid     curCollation;

    Assert(indexcol < index->nkeycolumns);

    curFamily = index->opfamily[indexcol];
    curCollation = index->indexcollations[indexcol];

    /* First check for boolean cases */
    if (IsBooleanOpfamily(curFamily))
    {
      Expr     *boolqual;

      boolqual = expand_boolean_index_clause((Node *) clause,
                           indexcol,
                           index);
      if (boolqual)
      {
        indexquals = lappend(indexquals,
                   make_simple_restrictinfo(boolqual));
        indexqualcols = lappend_int(indexqualcols, indexcol);
        continue;
      }
    }

    /*
     * Else it must be an opclause (usual case), ScalarArrayOp,
     * RowCompare, or NullTest
     */
    if (is_opclause(clause))
    {
      indexquals = list_concat(indexquals,
                   expand_indexqual_opclause(rinfo,
                                 curFamily,
                                 curCollation));
      /* expand_indexqual_opclause can produce multiple clauses */
      while (list_length(indexqualcols) < list_length(indexquals))
        indexqualcols = lappend_int(indexqualcols, indexcol);
    }
    else if (IsA(clause, ScalarArrayOpExpr))
    {
      /* no extra work at this time */
      indexquals = lappend(indexquals, rinfo);
      indexqualcols = lappend_int(indexqualcols, indexcol);
    }
    else if (IsA(clause, RowCompareExpr))
    {
      indexquals = lappend(indexquals,
                 expand_indexqual_rowcompare(rinfo,
                               index,
                               indexcol));
      indexqualcols = lappend_int(indexqualcols, indexcol);
    }
    else if (IsA(clause, NullTest))
    {
      Assert(index->amsearchnulls);
      indexquals = lappend(indexquals, rinfo);
      indexqualcols = lappend_int(indexqualcols, indexcol);
    }
    else
      elog(ERROR, "unsupported indexqual type: %d",
         (int) nodeTag(clause));
  }

  *indexquals_p = indexquals;
  *indexqualcols_p = indexqualcols;
}

/*
 * expand_boolean_index_clause
 *    Convert a clause recognized by match_boolean_index_clause into
 *    a boolean equality operator clause.
 *
 * Returns NULL if the clause isn't a boolean index qual.
 */
static Expr *
expand_boolean_index_clause(Node *clause,
              int indexcol,
              IndexOptInfo *index)
{
  /* Direct match? */
  if (match_index_to_operand(clause, indexcol, index))
  {
    /* convert to indexkey = TRUE */
    return make_opclause(BooleanEqualOperator, BOOLOID, false,
               (Expr *) clause,
               (Expr *) makeBoolConst(true, false),
               InvalidOid, InvalidOid);
  }
  /* NOT clause? */
  if (not_clause(clause))
  {
    Node     *arg = (Node *) get_notclausearg((Expr *) clause);

    /* It must have matched the indexkey */
    Assert(match_index_to_operand(arg, indexcol, index));
    /* convert to indexkey = FALSE */
    return make_opclause(BooleanEqualOperator, BOOLOID, false,
               (Expr *) arg,
               (Expr *) makeBoolConst(false, false),
               InvalidOid, InvalidOid);
  }
  if (clause && IsA(clause, BooleanTest))
  {
    BooleanTest *btest = (BooleanTest *) clause;
    Node     *arg = (Node *) btest->arg;

    /* It must have matched the indexkey */
    Assert(match_index_to_operand(arg, indexcol, index));
    if (btest->booltesttype == IS_TRUE)
    {
      /* convert to indexkey = TRUE */
      return make_opclause(BooleanEqualOperator, BOOLOID, false,
                 (Expr *) arg,
                 (Expr *) makeBoolConst(true, false),
                 InvalidOid, InvalidOid);
    }
    if (btest->booltesttype == IS_FALSE)
    {
      /* convert to indexkey = FALSE */
      return make_opclause(BooleanEqualOperator, BOOLOID, false,
                 (Expr *) arg,
                 (Expr *) makeBoolConst(false, false),
                 InvalidOid, InvalidOid);
    }
    /* Oops */
    Assert(false);
  }

  return NULL;
}

/*
 * expand_indexqual_opclause --- expand a single indexqual condition
 *    that is an operator clause
 *
 * The input is a single RestrictInfo, the output a list of RestrictInfos.
 *
 * In the base case this is just list_make1(), but we have to be prepared to
 * expand special cases that were accepted by match_special_index_operator().
 */
static List *
expand_indexqual_opclause(RestrictInfo *rinfo, Oid opfamily, Oid idxcollation)
{
  Expr     *clause = rinfo->clause;

  /* we know these will succeed */
  Node     *leftop = get_leftop(clause);
  Node     *rightop = get_rightop(clause);
  Oid     expr_op = ((OpExpr *) clause)->opno;
  Oid     expr_coll = ((OpExpr *) clause)->inputcollid;
  Const    *patt = (Const *) rightop;
  Const    *prefix = NULL;
  Pattern_Prefix_Status pstatus;

  /*
   * LIKE and regex operators are not members of any btree index opfamily,
   * but they can be members of opfamilies for more exotic index types such
   * as GIN.  Therefore, we should only do expansion if the operator is
   * actually not in the opfamily.  But checking that requires a syscache
   * lookup, so it's best to first see if the operator is one we are
   * interested in.
   */
  switch (expr_op)
  {
    case OID_TEXT_LIKE_OP:
    case OID_BPCHAR_LIKE_OP:
    case OID_NAME_LIKE_OP:
    case OID_BYTEA_LIKE_OP:
      if (!op_in_opfamily(expr_op, opfamily))
      {
        pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like, expr_coll,
                         &prefix, NULL);
        return prefix_quals(leftop, opfamily, idxcollation, prefix, pstatus);
      }
      break;

    case 3OID_TEXT_ICLIKE_OP3:
    case OID_BPCHAR_ICLIKE_OP:
    case OID_NAME_ICLIKE_OP:
      if (!op_in_opfamily(expr_op, opfamily))
      {
        /* the right-hand const is type text for all of these */
        pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like_IC, expr_coll,
                         &prefix, NULL);
        return prefix_quals(leftop, opfamily, idxcollation, prefix, pstatus);
      }
      break;

    case OID_TEXT_REGEXEQ_OP:
    case OID_BPCHAR_REGEXEQ_OP:
    case OID_NAME_REGEXEQ_OP:
      if (!op_in_opfamily(expr_op, opfamily))
      {
        /* the right-hand const is type text for all of these */
        pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex, expr_coll,
                         &prefix, NULL);
        return prefix_quals(leftop, opfamily, idxcollation, prefix, pstatus);
      }
      break;

    case 7OID_TEXT_ICREGEXEQ_OP7:
    case OID_BPCHAR_ICREGEXEQ_OP:
    case OID_NAME_ICREGEXEQ_OP:
      if (!op_in_opfamily(expr_op, opfamily))
      {
        /* the right-hand const is type text for all of these */
        pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex_IC, expr_coll,
                         &prefix, NULL);
        return prefix_quals(leftop, opfamily, idxcollation, prefix, pstatus);
      }
      break;

    case 0OID_INET_SUB_OP0:
    case OID_INET_SUBEQ_OP:
      if (!op_in_opfamily(expr_op, opfamily))
      {
        return network_prefix_quals(leftop, expr_op, opfamily,
                      patt->constvalue);
      }
      break;
  }

  /* Default case: just make a list of the unmodified indexqual */
  return list_make1(rinfo);
}

/*
 * expand_indexqual_rowcompare --- expand a single indexqual condition
 *    that is a RowCompareExpr
 *
 * This is a thin wrapper around adjust_rowcompare_for_index; we export the
 * latter so that createplan.c can use it to re-discover which columns of the
 * index are used by a row comparison indexqual.
 */
static RestrictInfo *
expand_indexqual_rowcompare(RestrictInfo *rinfo,
              IndexOptInfo *index,
              int indexcol)
{
  RowCompareExpr *clause = (RowCompareExpr *) rinfo->clause;
  Expr     *newclause;
  List     *indexcolnos;
  bool    var_on_left;

  newclause = adjust_rowcompare_for_index(clause,
                      index,
                      indexcol,
                      &indexcolnos,
                      &var_on_left);

  /*
   * If we didn't have to change the RowCompareExpr, return the original
   * RestrictInfo.
   */
  if (newclause == (Expr *) clause)
    return rinfo;

  /* Else we need a new RestrictInfo */
  return make_simple_restrictinfo(newclause);
}

/*
 * adjust_rowcompare_for_index --- expand a single indexqual condition
 *    that is a RowCompareExpr
 *
 * It's already known that the first column of the row comparison matches
 * the specified column of the index.  We can use additional columns of the
 * row comparison as index qualifications, so long as they match the index
 * in the "same direction", ie, the indexkeys are all on the same side of the
 * clause and the operators are all the same-type members of the opfamilies.
 * If all the columns of the RowCompareExpr match in this way, we just use it
 * as-is.  Otherwise, we build a shortened RowCompareExpr (if more than one
 * column matches) or a simple OpExpr (if the first-column match is all
 * there is).  In these cases the modified clause is always "<=" or ">="
 * even when the original was "<" or ">" --- this is necessary to match all
 * the rows that could match the original.  (We are essentially building a
 * lossy version of the row comparison when we do this.)
 *
 * *indexcolnos receives an integer list of the index column numbers (zero
 * based) used in the resulting expression.  The reason we need to return
 * that is that if the index is selected for use, createplan.c will need to
 * call this again to extract that list.  (This is a bit grotty, but row
 * comparison indexquals aren't used enough to justify finding someplace to
 * keep the information in the Path representation.)  Since createplan.c
 * also needs to know which side of the RowCompareExpr is the index side,
 * we also return *var_on_left_p rather than re-deducing that there.
 */
Expr *
adjust_rowcompare_for_index(RowCompareExpr *clause,
              IndexOptInfo *index,
              int indexcol,
              List **indexcolnos,
              bool *var_on_left_p)
{
  bool    var_on_left;
  int     op_strategy;
  Oid     op_lefttype;
  Oid     op_righttype;
  int     matching_cols;
  Oid     expr_op;
  List     *opfamilies;
  List     *lefttypes;
  List     *righttypes;
  List     *new_ops;
  ListCell   *largs_cell;
  ListCell   *rargs_cell;
  ListCell   *opnos_cell;
  ListCell   *collids_cell;

  /* We have to figure out (again) how the first col matches */
  var_on_left = match_index_to_operand((Node *) linitial(clause->largs),
                     indexcol, index);
  Assert(var_on_left ||
       match_index_to_operand((Node *) linitial(clause->rargs),
                  indexcol, index));
  *var_on_left_p = var_on_left;

  expr_op = linitial_oid(clause->opnos);
  if (!var_on_left)
    expr_op = get_commutator(expr_op);
  get_op_opfamily_properties(expr_op, index->opfamily[indexcol], false,
                 &op_strategy,
                 &op_lefttype,
                 &op_righttype);

  /* Initialize returned list of which index columns are used */
  *indexcolnos = list_make1_int(indexcol);

  /* Build lists of the opfamilies and operator datatypes in case needed */
  opfamilies = list_make1_oid(index->opfamily[indexcol]);
  lefttypes = list_make1_oid(op_lefttype);
  righttypes = list_make1_oid(op_righttype);

  /*
   * See how many of the remaining columns match some index column in the
   * same way.  As in match_clause_to_indexcol(), the "other" side of any
   * potential index condition is OK as long as it doesn't use Vars from the
   * indexed relation.
   */
  matching_cols = 1;
  largs_cell = lnext(list_head(clause->largs));
  rargs_cell = lnext(list_head(clause->rargs));
  opnos_cell = lnext(list_head(clause->opnos));
  collids_cell = lnext(list_head(clause->inputcollids));

  while (largs_cell != NULL)
  {
    Node     *varop;
    Node     *constop;
    int     i;

    expr_op = lfirst_oid(opnos_cell);
    if (var_on_left)
    {
      varop = (Node *) lfirst(largs_cell);
      constop = (Node *) lfirst(rargs_cell);
    }
    else
    {
      varop = (Node *) lfirst(rargs_cell);
      constop = (Node *) lfirst(largs_cell);
      /* indexkey is on right, so commute the operator */
      expr_op = get_commutator(expr_op);
      if (expr_op == InvalidOid)
        break;     /* operator is not usable */
    }
    if (bms_is_member(index->rel->relid, pull_varnos(constop)))
      break;       /* no good, Var on wrong side */
    if (contain_volatile_functions(constop))
      break;       /* no good, volatile comparison value */

    /*
     * The Var side can match any key column of the index.
     */
    for (i = 0; 668i < index->nkeycolumns; i++986)
    {
      if (match_index_to_operand(varop, i, index) &&
        get_op_opfamily_strategy(expr_op,
                     index->opfamily[i]) == op_strategy &&
        IndexCollMatchesExprColl653(index->indexcollations[i],
                     lfirst_oid(collids_cell)))

        break;
    }
    if (i >= index->nkeycolumns)
      break;        /* no match found */

    /* Add column number to returned list */
    *indexcolnos = lappend_int(*indexcolnos, i);

    /* Add opfamily and datatypes to lists */
    get_op_opfamily_properties(expr_op, index->opfamily[i], false,
                   &op_strategy,
                   &op_lefttype,
                   &op_righttype);
    opfamilies = lappend_oid(opfamilies, index->opfamily[i]);
    lefttypes = lappend_oid(lefttypes, op_lefttype);
    righttypes = lappend_oid(righttypes, op_righttype);

    /* This column matches, keep scanning */
    matching_cols++;
    largs_cell = lnext(largs_cell);
    rargs_cell = lnext(rargs_cell);
    opnos_cell = lnext(opnos_cell);
    collids_cell = lnext(collids_cell);
  }

  /* Return clause as-is if it's all usable as index quals */
  if (matching_cols == list_length(clause->opnos))
    return (Expr *) clause;

  /*
   * We have to generate a subset rowcompare (possibly just one OpExpr). The
   * painful part of this is changing < to <= or > to >=, so deal with that
   * first.
   */
  if (op_strategy == BTLessEqualStrategyNumber ||
    op_strategy == 5BTGreaterEqualStrategyNumber5)
  {
    /* easy, just use the same operators */
    new_ops = list_truncate(list_copy(clause->opnos), matching_cols);
  }
  else
  {
    ListCell   *opfamilies_cell;
    ListCell   *lefttypes_cell;
    ListCell   *righttypes_cell;

    if (op_strategy == BTLessStrategyNumber)
      op_strategy = BTLessEqualStrategyNumber;
    else if (op_strategy == BTGreaterStrategyNumber)
      op_strategy = BTGreaterEqualStrategyNumber;
    else
      elog(ERROR, "unexpected strategy number %d", op_strategy);
    new_ops = NIL;
    lefttypes_cell = list_head(lefttypes);
    righttypes_cell = list_head(righttypes);
    foreach(opfamilies_cell, opfamilies)
    {
      Oid     opfam = lfirst_oid(opfamilies_cell);
      Oid     lefttype = lfirst_oid(lefttypes_cell);
      Oid     righttype = lfirst_oid(righttypes_cell);

      expr_op = get_opfamily_member(opfam, lefttype, righttype,
                      op_strategy);
      if (!OidIsValid(expr_op))  /* should not happen */
        elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
           op_strategy, lefttype, righttype, opfam);
      if (!var_on_left)
      {
        expr_op = get_commutator(expr_op);
        if (!OidIsValid(expr_op))  /* should not happen */
          elog(ERROR, "could not find commutator of operator %d(%u,%u) of opfamily %u",
             op_strategy, lefttype, righttype, opfam);
      }
      new_ops = lappend_oid(new_ops, expr_op);
      lefttypes_cell = lnext(lefttypes_cell);
      righttypes_cell = lnext(righttypes_cell);
    }
  }

  /* If we have more than one matching col, create a subset rowcompare */
  if (matching_cols > 1)
  {
    RowCompareExpr *rc = makeNode(RowCompareExpr);

    if (var_on_left)
      rc->rctype = (RowCompareType) op_strategy;
    else
      rc->rctype = (op_strategy == BTLessEqualStrategyNumber) ?
        ROWCOMPARE_GE : ROWCOMPARE_LE;
    rc->opnos = new_ops;
    rc->opfamilies = list_truncate(list_copy(clause->opfamilies),
                     matching_cols);
    rc->inputcollids = list_truncate(list_copy(clause->inputcollids),
                     matching_cols);
    rc->largs = list_truncate(copyObject(clause->largs),
                  matching_cols);
    rc->rargs = list_truncate(copyObject(clause->rargs),
                  matching_cols);
    return (Expr *) rc;
  }
  else
  {
    return make_opclause(linitial_oid(new_ops), BOOLOID, false,
               copyObject(linitial(clause->largs)),
               copyObject(linitial(clause->rargs)),
               InvalidOid,
               linitial_oid(clause->inputcollids));
  }
}

/*
 * Given a fixed prefix that all the "leftop" values must have,
 * generate suitable indexqual condition(s).  opfamily is the index
 * operator family; we use it to deduce the appropriate comparison
 * operators and operand datatypes.  collation is the input collation to use.
 */
static List *
prefix_quals(Node *leftop, Oid opfamily, Oid collation,
       Const *prefix_const, Pattern_Prefix_Status pstatus)
{
  List     *result;
  Oid     datatype;
  Oid     oproid;
  Expr     *expr;
  FmgrInfo  ltproc;
  Const    *greaterstr;

  Assert(pstatus != Pattern_Prefix_None);

  switch (opfamily)
  {
    case TEXT_BTREE_FAM_OID:
    case TEXT_LSM_FAM_OID:
    case TEXT_PATTERN_BTREE_FAM_OID:
    case TEXT_PATTERN_LSM_FAM_OID:
    case TEXT_SPGIST_FAM_OID:
      datatype = TEXTOID;
      break;

    case BPCHAR_BTREE_FAM_OID:
    case BPCHAR_LSM_FAM_OID:
    case BPCHAR_PATTERN_BTREE_FAM_OID:
    case BPCHAR_PATTERN_LSM_FAM_OID:
      datatype = BPCHAROID;
      break;

    case NAME_BTREE_FAM_OID:
    case NAME_LSM_FAM_OID:
      datatype = NAMEOID;
      break;

    case BYTEA_BTREE_FAM_OID:
    case BYTEA_LSM_FAM_OID:
      datatype = BYTEAOID;
      break;

    default:
      /* shouldn't get here */
      elog(ERROR, "unexpected opfamily: %u", opfamily);
      return NIL;
  }

  /*
   * If necessary, coerce the prefix constant to the right type. The given
   * prefix constant is either text or bytea type.
   */
  if (prefix_const->consttype != datatype)
  {
    char     *prefix;

    switch (prefix_const->consttype)
    {
      case TEXTOID:
        prefix = TextDatumGetCString(prefix_const->constvalue);
        break;
      case BYTEAOID:
        prefix = DatumGetCString(DirectFunctionCall1(byteaout,
                               prefix_const->constvalue));
        break;
      default:
        elog(ERROR, "unexpected const type: %u",
           prefix_const->consttype);
        return NIL;
    }
    prefix_const = string_to_const(prefix, datatype);
    pfree(prefix);
  }

  /*
   * If we found an exact-match pattern, generate an "=" indexqual.
   */
  if (pstatus == Pattern_Prefix_Exact)
  {
    oproid = get_opfamily_member(opfamily, datatype, datatype,
                   BTEqualStrategyNumber);
    if (oproid == InvalidOid)
      elog(ERROR, "no = operator for opfamily %u", opfamily);
    expr = make_opclause(oproid, BOOLOID, false,
               (Expr *) leftop, (Expr *) prefix_const,
               InvalidOid, collation);
    result = list_make1(make_simple_restrictinfo(expr));
    return result;
  }

  /*
   * Otherwise, we have a nonempty required prefix of the values.
   *
   * We can always say "x >= prefix".
   */
  oproid = get_opfamily_member(opfamily, datatype, datatype,
                 BTGreaterEqualStrategyNumber);
  if (oproid == InvalidOid)
    elog(ERROR, "no >= operator for opfamily %u", opfamily);
  expr = make_opclause(oproid, BOOLOID, false,
             (Expr *) leftop, (Expr *) prefix_const,
             InvalidOid, collation);
  result = list_make1(make_simple_restrictinfo(expr));

  /*-------
   * If we can create a string larger than the prefix, we can say
   * "x < greaterstr".  NB: we rely on make_greater_string() to generate
   * a guaranteed-greater string, not just a probably-greater string.
   * In general this is only guaranteed in C locale, so we'd better be
   * using a C-locale index collation.
   *-------
   */
  oproid = get_opfamily_member(opfamily, datatype, datatype,
                 BTLessStrategyNumber);
  if (oproid == InvalidOid)
    elog(ERROR, "no < operator for opfamily %u", opfamily);
  fmgr_info(get_opcode(oproid), &ltproc);
  greaterstr = make_greater_string(prefix_const, &ltproc, collation);
  if (greaterstr)
  {
    expr = make_opclause(oproid, BOOLOID, false,
               (Expr *) leftop, (Expr *) greaterstr,
               InvalidOid, collation);
    result = lappend(result, make_simple_restrictinfo(expr));
  }

  return result;
}

/*
 * Given a leftop and a rightop, and an inet-family sup/sub operator,
 * generate suitable indexqual condition(s).  expr_op is the original
 * operator, and opfamily is the index opfamily.
 */
static List *
network_prefix_quals(Node *leftop, Oid expr_op, Oid opfamily, Datum rightop)
{
  bool    is_eq;
  Oid     datatype;
  Oid     opr1oid;
  Oid     opr2oid;
  Datum   opr1right;
  Datum   opr2right;
  List     *result;
  Expr     *expr;

  switch (expr_op)
  {
    case OID_INET_SUB_OP:
      datatype = INETOID;
      is_eq = false;
      break;
    case OID_INET_SUBEQ_OP:
      datatype = INETOID;
      is_eq = true;
      break;
    default:
      elog(ERROR, "unexpected operator: %u", expr_op);
      return NIL;
  }

  /*
   * create clause "key >= network_scan_first( rightop )", or ">" if the
   * operator disallows equality.
   */
  if (is_eq)
  {
    opr1oid = get_opfamily_member(opfamily, datatype, datatype,
                    BTGreaterEqualStrategyNumber);
    if (opr1oid == InvalidOid)
      elog(ERROR, "no >= operator for opfamily %u", opfamily);
  }
  else
  {
    opr1oid = get_opfamily_member(opfamily, datatype, datatype,
                    BTGreaterStrategyNumber);
    if (opr1oid == InvalidOid)
      elog(ERROR, "no > operator for opfamily %u", opfamily);
  }

  opr1right = network_scan_first(rightop);

  expr = make_opclause(opr1oid, BOOLOID, false,
             (Expr *) leftop,
             (Expr *) makeConst(datatype, -1,
                      InvalidOid, /* not collatable */
                      -1, opr1right,
                      false, false),
             InvalidOid, InvalidOid);
  result = list_make1(make_simple_restrictinfo(expr));

  /* create clause "key <= network_scan_last( rightop )" */

  opr2oid = get_opfamily_member(opfamily, datatype, datatype,
                  BTLessEqualStrategyNumber);
  if (opr2oid == InvalidOid)
    elog(ERROR, "no <= operator for opfamily %u", opfamily);

  opr2right = network_scan_last(rightop);

  expr = make_opclause(opr2oid, BOOLOID, false,
             (Expr *) leftop,
             (Expr *) makeConst(datatype, -1,
                      InvalidOid, /* not collatable */
                      -1, opr2right,
                      false, false),
             InvalidOid, InvalidOid);
  result = lappend(result, make_simple_restrictinfo(expr));

  return result;
}

/*
 * Handy subroutines for match_special_index_operator() and friends.
 */

/*
 * Generate a Datum of the appropriate type from a C string.
 * Note that all of the supported types are pass-by-ref, so the
 * returned value should be pfree'd if no longer needed.
 */
static Datum
string_to_datum(const char *str, Oid datatype)
{
  /*
   * We cheat a little by assuming that CStringGetTextDatum() will do for
   * bpchar and varchar constants too...
   */
  if (datatype == NAMEOID)
    return DirectFunctionCall1(namein, CStringGetDatum(str));
  else if (datatype == BYTEAOID)
    return DirectFunctionCall1(byteain, CStringGetDatum(str));
  else
    return CStringGetTextDatum(str);
}

/*
 * Generate a Const node of the appropriate type from a C string.
 */
static Const *
string_to_const(const char *str, Oid datatype)
{
  Datum   conval = string_to_datum(str, datatype);
  Oid     collation;
  int     constlen;

  /*
   * We only need to support a few datatypes here, so hard-wire properties
   * instead of incurring the expense of catalog lookups.
   */
  switch (datatype)
  {
    case TEXTOID:
    case VARCHAROID:
    case BPCHAROID:
      collation = DEFAULT_COLLATION_OID;
      constlen = -1;
      break;

    case NAMEOID:
      collation = InvalidOid;
      constlen = NAMEDATALEN;
      break;

    case BYTEAOID:
      collation = InvalidOid;
      constlen = -1;
      break;

    default:
      elog(ERROR, "unexpected datatype in string_to_const: %u",
         datatype);
      return NULL;
  }

  return makeConst(datatype, -1, collation, constlen,
           conval, false, false);
}

YugabyteDB (2.13.1.0-b60, 21121d69985fbf76aa6958d8f04a9bfa936293b5)

Coverage Report

Created: 2022-03-22 16:43