// Copyright 2025 Google LLC
//
// 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.

syntax = "proto3";

package google.spanner.v1;

import "google/api/field_behavior.proto";
import "google/protobuf/duration.proto";
import "google/protobuf/timestamp.proto";

option csharp_namespace = "Google.Cloud.Spanner.V1";
option go_package = "cloud.google.com/go/spanner/apiv1/spannerpb;spannerpb";
option java_multiple_files = true;
option java_outer_classname = "TransactionProto";
option java_package = "com.google.spanner.v1";
option php_namespace = "Google\\Cloud\\Spanner\\V1";
option ruby_package = "Google::Cloud::Spanner::V1";

// Options to use for transactions.
message TransactionOptions {
  // Message type to initiate a read-write transaction. Currently this
  // transaction type has no options.
  message ReadWrite {
    // `ReadLockMode` is used to set the read lock mode for read-write
    // transactions.
    enum ReadLockMode {
      // Default value.
      //
      // * If isolation level is
      //   [REPEATABLE_READ][google.spanner.v1.TransactionOptions.IsolationLevel.REPEATABLE_READ],
      //   then it is an error to specify `read_lock_mode`. Locking semantics
      //   default to `OPTIMISTIC`. No validation checks are done for reads,
      //   except to validate that the data that was served at the snapshot time
      //   is unchanged at commit time in the following cases:
      //     1. reads done as part of queries that use `SELECT FOR UPDATE`
      //     2. reads done as part of statements with a `LOCK_SCANNED_RANGES`
      //        hint
      //     3. reads done as part of DML statements
      // * At all other isolation levels, if `read_lock_mode` is the default
      //   value, then pessimistic read locks are used.
      READ_LOCK_MODE_UNSPECIFIED = 0;

      // Pessimistic lock mode.
      //
      // Read locks are acquired immediately on read.
      // Semantics described only applies to
      // [SERIALIZABLE][google.spanner.v1.TransactionOptions.IsolationLevel.SERIALIZABLE]
      // isolation.
      PESSIMISTIC = 1;

      // Optimistic lock mode.
      //
      // Locks for reads within the transaction are not acquired on read.
      // Instead the locks are acquired on a commit to validate that
      // read/queried data has not changed since the transaction started.
      // Semantics described only applies to
      // [SERIALIZABLE][google.spanner.v1.TransactionOptions.IsolationLevel.SERIALIZABLE]
      // isolation.
      OPTIMISTIC = 2;
    }

    // Read lock mode for the transaction.
    ReadLockMode read_lock_mode = 1;

    // Optional. Clients should pass the transaction ID of the previous
    // transaction attempt that was aborted if this transaction is being
    // executed on a multiplexed session.
    bytes multiplexed_session_previous_transaction_id = 2
        [(google.api.field_behavior) = OPTIONAL];
  }

  // Message type to initiate a Partitioned DML transaction.
  message PartitionedDml {}

  // Message type to initiate a read-only transaction.
  message ReadOnly {
    // How to choose the timestamp for the read-only transaction.
    oneof timestamp_bound {
      // Read at a timestamp where all previously committed transactions
      // are visible.
      bool strong = 1;

      // Executes all reads at a timestamp >= `min_read_timestamp`.
      //
      // This is useful for requesting fresher data than some previous
      // read, or data that is fresh enough to observe the effects of some
      // previously committed transaction whose timestamp is known.
      //
      // Note that this option can only be used in single-use transactions.
      //
      // A timestamp in RFC3339 UTC \"Zulu\" format, accurate to nanoseconds.
      // Example: `"2014-10-02T15:01:23.045123456Z"`.
      google.protobuf.Timestamp min_read_timestamp = 2;

      // Read data at a timestamp >= `NOW - max_staleness`
      // seconds. Guarantees that all writes that have committed more
      // than the specified number of seconds ago are visible. Because
      // Cloud Spanner chooses the exact timestamp, this mode works even if
      // the client's local clock is substantially skewed from Cloud Spanner
      // commit timestamps.
      //
      // Useful for reading the freshest data available at a nearby
      // replica, while bounding the possible staleness if the local
      // replica has fallen behind.
      //
      // Note that this option can only be used in single-use
      // transactions.
      google.protobuf.Duration max_staleness = 3;

      // Executes all reads at the given timestamp. Unlike other modes,
      // reads at a specific timestamp are repeatable; the same read at
      // the same timestamp always returns the same data. If the
      // timestamp is in the future, the read is blocked until the
      // specified timestamp, modulo the read's deadline.
      //
      // Useful for large scale consistent reads such as mapreduces, or
      // for coordinating many reads against a consistent snapshot of the
      // data.
      //
      // A timestamp in RFC3339 UTC \"Zulu\" format, accurate to nanoseconds.
      // Example: `"2014-10-02T15:01:23.045123456Z"`.
      google.protobuf.Timestamp read_timestamp = 4;

      // Executes all reads at a timestamp that is `exact_staleness`
      // old. The timestamp is chosen soon after the read is started.
      //
      // Guarantees that all writes that have committed more than the
      // specified number of seconds ago are visible. Because Cloud Spanner
      // chooses the exact timestamp, this mode works even if the client's
      // local clock is substantially skewed from Cloud Spanner commit
      // timestamps.
      //
      // Useful for reading at nearby replicas without the distributed
      // timestamp negotiation overhead of `max_staleness`.
      google.protobuf.Duration exact_staleness = 5;
    }

    // If true, the Cloud Spanner-selected read timestamp is included in
    // the [Transaction][google.spanner.v1.Transaction] message that describes
    // the transaction.
    bool return_read_timestamp = 6;
  }

  // `IsolationLevel` is used when setting `isolation_level` for a transaction.
  enum IsolationLevel {
    // Default value.
    //
    // If the value is not specified, the `SERIALIZABLE` isolation level is
    // used.
    ISOLATION_LEVEL_UNSPECIFIED = 0;

    // All transactions appear as if they executed in a serial order, even if
    // some of the reads, writes, and other operations of distinct transactions
    // actually occurred in parallel. Spanner assigns commit timestamps that
    // reflect the order of committed transactions to implement this property.
    // Spanner offers a stronger guarantee than serializability called external
    // consistency. For more information, see
    // [TrueTime and external
    // consistency](https://cloud.google.com/spanner/docs/true-time-external-consistency#serializability).
    SERIALIZABLE = 1;

    // All reads performed during the transaction observe a consistent snapshot
    // of the database, and the transaction is only successfully committed in
    // the absence of conflicts between its updates and any concurrent updates
    // that have occurred since that snapshot. Consequently, in contrast to
    // `SERIALIZABLE` transactions, only write-write conflicts are detected in
    // snapshot transactions.
    //
    // This isolation level does not support Read-only and Partitioned DML
    // transactions.
    //
    // When `REPEATABLE_READ` is specified on a read-write transaction, the
    // locking semantics default to `OPTIMISTIC`.
    REPEATABLE_READ = 2;
  }

  // Required. The type of transaction.
  oneof mode {
    // Transaction may write.
    //
    // Authorization to begin a read-write transaction requires
    // `spanner.databases.beginOrRollbackReadWriteTransaction` permission
    // on the `session` resource.
    ReadWrite read_write = 1;

    // Partitioned DML transaction.
    //
    // Authorization to begin a Partitioned DML transaction requires
    // `spanner.databases.beginPartitionedDmlTransaction` permission
    // on the `session` resource.
    PartitionedDml partitioned_dml = 3;

    // Transaction does not write.
    //
    // Authorization to begin a read-only transaction requires
    // `spanner.databases.beginReadOnlyTransaction` permission
    // on the `session` resource.
    ReadOnly read_only = 2;
  }

  // When `exclude_txn_from_change_streams` is set to `true`, it prevents read
  // or write transactions from being tracked in change streams.
  //
  // * If the DDL option `allow_txn_exclusion` is set to `true`, then the
  // updates
  //  made within this transaction aren't recorded in the change stream.
  //
  // * If you don't set the DDL option `allow_txn_exclusion` or if it's
  //  set to `false`, then the updates made within this transaction are
  //  recorded in the change stream.
  //
  // When `exclude_txn_from_change_streams` is set to `false` or not set,
  // modifications from this transaction are recorded in all change streams
  // that are tracking columns modified by these transactions.
  //
  // The `exclude_txn_from_change_streams` option can only be specified
  // for read-write or partitioned DML transactions, otherwise the API returns
  // an `INVALID_ARGUMENT` error.
  bool exclude_txn_from_change_streams = 5;

  // Isolation level for the transaction.
  IsolationLevel isolation_level = 6;
}

// A transaction.
message Transaction {
  // `id` may be used to identify the transaction in subsequent
  // [Read][google.spanner.v1.Spanner.Read],
  // [ExecuteSql][google.spanner.v1.Spanner.ExecuteSql],
  // [Commit][google.spanner.v1.Spanner.Commit], or
  // [Rollback][google.spanner.v1.Spanner.Rollback] calls.
  //
  // Single-use read-only transactions do not have IDs, because
  // single-use transactions do not support multiple requests.
  bytes id = 1;

  // For snapshot read-only transactions, the read timestamp chosen
  // for the transaction. Not returned by default: see
  // [TransactionOptions.ReadOnly.return_read_timestamp][google.spanner.v1.TransactionOptions.ReadOnly.return_read_timestamp].
  //
  // A timestamp in RFC3339 UTC \"Zulu\" format, accurate to nanoseconds.
  // Example: `"2014-10-02T15:01:23.045123456Z"`.
  google.protobuf.Timestamp read_timestamp = 2;

  // A precommit token is included in the response of a BeginTransaction
  // request if the read-write transaction is on a multiplexed session and
  // a mutation_key was specified in the
  // [BeginTransaction][google.spanner.v1.BeginTransactionRequest].
  // The precommit token with the highest sequence number from this transaction
  // attempt should be passed to the [Commit][google.spanner.v1.Spanner.Commit]
  // request for this transaction.
  MultiplexedSessionPrecommitToken precommit_token = 3;
}

// This message is used to select the transaction in which a
// [Read][google.spanner.v1.Spanner.Read] or
// [ExecuteSql][google.spanner.v1.Spanner.ExecuteSql] call runs.
//
// See [TransactionOptions][google.spanner.v1.TransactionOptions] for more
// information about transactions.
message TransactionSelector {
  // If no fields are set, the default is a single use transaction
  // with strong concurrency.
  oneof selector {
    // Execute the read or SQL query in a temporary transaction.
    // This is the most efficient way to execute a transaction that
    // consists of a single SQL query.
    TransactionOptions single_use = 1;

    // Execute the read or SQL query in a previously-started transaction.
    bytes id = 2;

    // Begin a new transaction and execute this read or SQL query in
    // it. The transaction ID of the new transaction is returned in
    // [ResultSetMetadata.transaction][google.spanner.v1.ResultSetMetadata.transaction],
    // which is a [Transaction][google.spanner.v1.Transaction].
    TransactionOptions begin = 3;
  }
}

// When a read-write transaction is executed on a multiplexed session,
// this precommit token is sent back to the client
// as a part of the [Transaction][google.spanner.v1.Transaction] message in the
// [BeginTransaction][google.spanner.v1.BeginTransactionRequest] response and
// also as a part of the [ResultSet][google.spanner.v1.ResultSet] and
// [PartialResultSet][google.spanner.v1.PartialResultSet] responses.
message MultiplexedSessionPrecommitToken {
  // Opaque precommit token.
  bytes precommit_token = 1;

  // An incrementing seq number is generated on every precommit token
  // that is returned. Clients should remember the precommit token with the
  // highest sequence number from the current transaction attempt.
  int32 seq_num = 2;
}
