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/docdb/intent.h"

#include <string>

#include <glog/logging.h>

#include "yb/common/row_mark.h"

#include "yb/common/transaction.h"

#include "yb/docdb/value_type.h"

#include "yb/gutil/endian.h"

#include "yb/util/result.h"

#include "yb/util/status_format.h"

namespace yb {

namespace docdb {

Result<DecodedIntentKey> DecodeIntentKey(const Slice &encoded_intent_key) {

  DecodedIntentKey result;

  auto& intent_prefix = result.intent_prefix;

  intent_prefix = encoded_intent_key;

  size_t doc_ht_size = 0;

  RETURN_NOT_OK(DocHybridTime::CheckAndGetEncodedSize(intent_prefix, &doc_ht_size));

  // There should always be 3 bytes present before teh start of the doc_ht:

  // 1. ValueType::kIntentTypeSet

  // 2. the corresponding value for ValueType::kIntentTypeSet

  // 3. ValueType::kHybridTime

  constexpr int kBytesBeforeDocHt = 3;

  if (intent_prefix.size() < doc_ht_size + kBytesBeforeDocHt) {

    return STATUS_FORMAT(

        Corruption, "Intent key is too short: $0 bytes", encoded_intent_key.size());

  }

  intent_prefix.remove_suffix(doc_ht_size + kBytesBeforeDocHt);

  RETURN_NOT_OK(result.doc_ht.FullyDecodeFrom(

      Slice(intent_prefix.data() + intent_prefix.size() + kBytesBeforeDocHt, doc_ht_size)));

  auto* prefix_end = intent_prefix.end();

  if (prefix_end[2] != ValueTypeAsChar::kHybridTime)

    return STATUS_FORMAT(Corruption, "Expecting hybrid time with ValueType $0, found $1",

        ValueType::kHybridTime, static_cast<ValueType>(prefix_end[2]));

  if (prefix_end[0] != ValueTypeAsChar::kIntentTypeSet) {

    if (prefix_end[0] == ValueTypeAsChar::kObsoleteIntentType) {

      result.intent_types = ObsoleteIntentTypeToSet(prefix_end[1]);

    } else if (prefix_end[0] == ValueTypeAsChar::kObsoleteIntentTypeSet) {

      result.intent_types = ObsoleteIntentTypeSetToNew(prefix_end[1]);

    } else {

      return STATUS_FORMAT(

          Corruption,

          "Expecting intent type set ($0) or intent type ($1) or obsolete intent type set ($2), "

              "found $3",

          ValueType::kIntentTypeSet, ValueType::kObsoleteIntentType,

          ValueType::kObsoleteIntentTypeSet, static_cast<ValueType>(prefix_end[0]));

    }

  } else {

    result.intent_types = IntentTypeSet(prefix_end[1]);

  }

  return result;

}

Result<TransactionId> DecodeTransactionIdFromIntentValue(Slice* intent_value) {

  if (intent_value->empty()) {

    return STATUS_FORMAT(Corruption, "Expecting intent value to start with ValueType $0, but it is "

        "empty", ValueType::kTransactionId);

  } else if (*intent_value->data() != ValueTypeAsChar::kTransactionId) {

    return STATUS_FORMAT(Corruption, "Expecting intent key to start with ValueType $0, found $1",

        ValueType::kTransactionId, static_cast<ValueType>(*intent_value->data()));

  } else {

    intent_value->consume_byte();

  }

  return DecodeTransactionId(intent_value);

}

IntentTypeSet AllStrongIntents() {

  return IntentTypeSet({IntentType::kStrongRead, IntentType::kStrongWrite});

}

IntentTypeSet GetStrongIntentTypeSet(

    IsolationLevel level,

    OperationKind operation_kind,

    RowMarkType row_mark) {

  if (IsValidRowMarkType(row_mark)) {

    // Mapping of postgres locking levels to DocDB intent types is described in details by the

    // following comment https://github.com/yugabyte/yugabyte-db/issues/1199#issuecomment-501041018

    switch (row_mark) {

      case RowMarkType::ROW_MARK_EXCLUSIVE:

        // FOR UPDATE: strong read + strong write lock on the DocKey,

        //             as if we're replacing or deleting the entire row in DocDB.

        return IntentTypeSet({IntentType::kStrongRead, IntentType::kStrongWrite});

      case RowMarkType::ROW_MARK_NOKEYEXCLUSIVE:

        // FOR NO KEY UPDATE: strong read + weak write lock on the DocKey, as if we're reading

        //                    the entire row and then writing only a subset of columns in DocDB.

        return IntentTypeSet({IntentType::kStrongRead, IntentType::kWeakWrite});

      case RowMarkType::ROW_MARK_SHARE:

        // FOR SHARE: strong read on the DocKey, as if we're reading the entire row in DocDB.

        return IntentTypeSet({IntentType::kStrongRead});

      case RowMarkType::ROW_MARK_KEYSHARE:

        // FOR KEY SHARE: weak read lock on the DocKey, preventing the entire row from being

        //               replaced / deleted, as if we're simply reading some of the column.

        //               This is the type of locking that is used by foreign keys, so this will

        //               prevent the referenced row from disappearing. The reason it does not

        //               conflict with the FOR NO KEY UPDATE above is conceptually the following:

        //               an operation that reads the entire row and then writes a subset of columns

        //               (FOR NO KEY UPDATE) does not have to conflict with an operation that could

        //               be reading a different subset of columns (FOR KEY SHARE).

        return IntentTypeSet({IntentType::kWeakRead});

      default:

        // We shouldn't get here because other row lock types are disabled at the postgres level.

        LOG(DFATAL) << "Unsupported row lock of type " << RowMarkType_Name(row_mark);

        break;

    }

  }

  switch (level) {

    case IsolationLevel::READ_COMMITTED:

    case IsolationLevel::SNAPSHOT_ISOLATION:

      return IntentTypeSet({IntentType::kStrongRead, IntentType::kStrongWrite});

    case IsolationLevel::SERIALIZABLE_ISOLATION:

      switch (operation_kind) {

        case OperationKind::kRead:

          return IntentTypeSet({IntentType::kStrongRead});

        case OperationKind::kWrite:

          return IntentTypeSet({IntentType::kStrongWrite});

      }

      FATAL_INVALID_ENUM_VALUE(OperationKind, operation_kind);

    case IsolationLevel::NON_TRANSACTIONAL:

      LOG(DFATAL) << "GetStrongIntentTypeSet invoked for non transactional isolation";

      return IntentTypeSet();

  }

  FATAL_INVALID_ENUM_VALUE(IsolationLevel, level);

}

bool HasStrong(IntentTypeSet inp) {

  return (inp & AllStrongIntents()).Any();

}

#define INTENT_VALUE_SCHECK(lhs, op, rhs, msg) \

  BOOST_PP_CAT(SCHECK_, op)(lhs, \

                            rhs, \

                            Corruption, \

                            Format("Bad intent value, $0 in $1, transaction: $2", \

                                   msg, \

                                   encoded_intent_value.ToDebugHexString(), \

                                   transaction_id_slice.ToDebugHexString()))

Result<DecodedIntentValue> DecodeIntentValue(

    const Slice& encoded_intent_value, const Slice* verify_transaction_id_slice,

    bool has_strong_intent) {

  DecodedIntentValue decoded_value;

  auto intent_value = encoded_intent_value;

  auto transaction_id_slice = Slice();

  if (verify_transaction_id_slice) {

    transaction_id_slice = *verify_transaction_id_slice;

    RETURN_NOT_OK(intent_value.consume_byte(ValueTypeAsChar::kTransactionId));

    INTENT_VALUE_SCHECK(intent_value.starts_with(transaction_id_slice), EQ, true,

        "wrong transaction id");

    intent_value.remove_prefix(TransactionId::StaticSize());

  } else {

    decoded_value.transaction_id = VERIFY_RESULT(DecodeTransactionIdFromIntentValue(&intent_value));

    transaction_id_slice = decoded_value.transaction_id.AsSlice();

  }

  if (intent_value.TryConsumeByte(ValueTypeAsChar::kSubTransactionId)) {

    decoded_value.subtransaction_id = Load<SubTransactionId, BigEndian>(intent_value.data());

    intent_value.remove_prefix(sizeof(SubTransactionId));

  } else {

    decoded_value.subtransaction_id = kMinSubTransactionId;

  }

  if (has_strong_intent) {

    RETURN_NOT_OK(intent_value.consume_byte(ValueTypeAsChar::kWriteId));

    INTENT_VALUE_SCHECK(intent_value.size(), GE, sizeof(IntraTxnWriteId), "write id expected");

    decoded_value.write_id = BigEndian::Load32(intent_value.data());

    intent_value.remove_prefix(sizeof(IntraTxnWriteId));

  }

  decoded_value.body = intent_value;

  return decoded_value;

}

IntentTypeSet ObsoleteIntentTypeToSet(uint8_t obsolete_intent_type) {

  constexpr int kWeakIntentFlag         = 0b000;

  constexpr int kStrongIntentFlag       = 0b001;

  constexpr int kWriteIntentFlag        = 0b010;

  constexpr int kSnapshotIntentFlag     = 0b100;

  // Actually we have only 2 types of obsolete intent types that could be present.

  // Strong and weak snapshot writes.

  if (obsolete_intent_type == (kStrongIntentFlag | kWriteIntentFlag | kSnapshotIntentFlag)) {

    return IntentTypeSet({IntentType::kStrongRead, IntentType::kStrongWrite});

  } else if (obsolete_intent_type == (kWeakIntentFlag | kWriteIntentFlag | kSnapshotIntentFlag)) {

    return IntentTypeSet({IntentType::kWeakRead, IntentType::kWeakWrite});

  }

  LOG(DFATAL) << "Unexpected obsolete intent type: " << static_cast<int>(obsolete_intent_type);

  return IntentTypeSet();

}

IntentTypeSet ObsoleteIntentTypeSetToNew(uint8_t obsolete_intent_type_set) {

  IntentTypeSet result;

  for (size_t idx = 0; idx != 4; ++idx) {

    if (obsolete_intent_type_set & (1 << idx)) {

      // We swap two bits in every index because their meanings have changed places between the

      // obsolete vs. new format.

      result.Set(static_cast<IntentType>(((idx >> 1) | (idx << 1)) & 3));

    }

  }

  return result;

}

bool IntentValueType(char ch) {

  return ch == ValueTypeAsChar::kIntentTypeSet ||

         ch == ValueTypeAsChar::kObsoleteIntentTypeSet ||

         ch == ValueTypeAsChar::kObsoleteIntentType;

}

}  // namespace docdb

}  // namespace yb