YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

//--------------------------------------------------------------------------------------------------

// Copyright (c) YugaByte, Inc.

//

// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except

// in compliance with the License.  You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software distributed under the License

// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express

// or implied.  See the License for the specific language governing permissions and limitations

// under the License.

//

//--------------------------------------------------------------------------------------------------

#include "yb/yql/pggate/pg_select.h"

#include "yb/client/yb_op.h"

#include "yb/yql/pggate/pg_select_index.h"

#include "yb/yql/pggate/util/pg_doc_data.h"

namespace yb {

namespace pggate {

using std::make_shared;

//--------------------------------------------------------------------------------------------------

// PgSelect

//--------------------------------------------------------------------------------------------------

PgSelect::PgSelect(PgSession::ScopedRefPtr pg_session, const PgObjectId& table_id,

                   const PgObjectId& index_id, const PgPrepareParameters *prepare_params)

    : PgDmlRead(pg_session, table_id, index_id, prepare_params) {}

PgSelect::~PgSelect() {

}

Result<PgTableDescPtr> PgSelect::LoadTable() {

  return pg_session_->LoadTable(table_id_);

}

bool PgSelect::UseSecondaryIndex() const {

  return prepare_params_.use_secondary_index;

}

Status PgSelect::Prepare() {

  // Prepare target and bind descriptors.

  target_ = PgTable(VERIFY_RESULT(LoadTable()));

  if (!UseSecondaryIndex()) {

    bind_ = target_;

  } else {

    bind_ = PgTable(nullptr);

    // Create secondary index query.

    secondary_index_query_ =

      std::make_unique<PgSelectIndex>(pg_session_, table_id_, index_id_, &prepare_params_);

  }

  // Allocate READ requests to send to DocDB.

  auto read_op = std::make_shared<PgsqlReadOp>(*target_);

  read_req_ = std::shared_ptr<PgsqlReadRequestPB>(read_op, &read_op->read_request());

  auto doc_op = std::make_shared<PgDocReadOp>(pg_session_, &target_, std::move(read_op));

  // Prepare the index selection if this operation is using the index.

  RETURN_NOT_OK(PrepareSecondaryIndex());

  // Prepare binds for the request.

  PrepareBinds();

  doc_op_ = doc_op;

  return Status::OK();

}

Status PgSelect::PrepareSecondaryIndex() {

  if (!secondary_index_query_) {

    // This DML statement is not using secondary index.

    return Status::OK();

  }

  // Prepare the index operation to read ybctids from the index table. There are two different

  // scenarios on how ybctids are requested.

  // - Due to an optimization in DocDB, for colocated tables (both system and user colocated), index

  //   request is sent as a part of the actual read request using protobuf field

  //   "PgsqlReadRequestPB::index_request"

  //

  //   For this case, "mutable_index_request" is allocated here and passed to PgSelectIndex node to

  //   fill in with bind-values when necessary.

  //

  // - For regular tables, the index subquery will send separate request to tablet servers collect

  //   batches of ybctids which is then used by 'this' outer select to query actual data.

  std::shared_ptr<PgsqlReadRequestPB> index_req = nullptr;

  if (prepare_params_.querying_colocated_table) {

    // Allocate "index_request" and pass to PgSelectIndex.

    index_req = std::shared_ptr<PgsqlReadRequestPB>(read_req_, read_req_->mutable_index_request());

  }

  // Prepare subquery. When index_req is not null, it is part of 'this' SELECT request. When it

  // is nullptr, the subquery will create its own doc_op to run a separate read request.

  return secondary_index_query_->PrepareSubquery(index_req);

}

}  // namespace pggate

}  // namespace yb