Package com.google.spanner.v1

Class TransactionOptions

  • All Implemented Interfaces:
    com.google.protobuf.Message, com.google.protobuf.MessageLite, com.google.protobuf.MessageLiteOrBuilder, com.google.protobuf.MessageOrBuilder, TransactionOptionsOrBuilder, Serializable
    public final class TransactionOptions
extends com.google.protobuf.GeneratedMessageV3
implements TransactionOptionsOrBuilder
     Transactions:

 Each session can have at most one active transaction at a time (note that
 standalone reads and queries use a transaction internally and do count
 towards the one transaction limit). After the active transaction is
 completed, the session can immediately be re-used for the next transaction.
 It is not necessary to create a new session for each transaction.

 Transaction modes:

 Cloud Spanner supports three transaction modes:

   1. Locking read-write. This type of transaction is the only way
      to write data into Cloud Spanner. These transactions rely on
      pessimistic locking and, if necessary, two-phase commit.
      Locking read-write transactions may abort, requiring the
      application to retry.

   2. Snapshot read-only. Snapshot read-only transactions provide guaranteed
      consistency across several reads, but do not allow
      writes. Snapshot read-only transactions can be configured to read at
      timestamps in the past, or configured to perform a strong read
      (where Spanner will select a timestamp such that the read is
      guaranteed to see the effects of all transactions that have committed
      before the start of the read). Snapshot read-only transactions do not
      need to be committed.

      Queries on change streams must be performed with the snapshot read-only
      transaction mode, specifying a strong read. Please see
      [TransactionOptions.ReadOnly.strong][google.spanner.v1.TransactionOptions.ReadOnly.strong]
      for more details.

   3. Partitioned DML. This type of transaction is used to execute
      a single Partitioned DML statement. Partitioned DML partitions
      the key space and runs the DML statement over each partition
      in parallel using separate, internal transactions that commit
      independently. Partitioned DML transactions do not need to be
      committed.

 For transactions that only read, snapshot read-only transactions
 provide simpler semantics and are almost always faster. In
 particular, read-only transactions do not take locks, so they do
 not conflict with read-write transactions. As a consequence of not
 taking locks, they also do not abort, so retry loops are not needed.

 Transactions may only read-write data in a single database. They
 may, however, read-write data in different tables within that
 database.

 Locking read-write transactions:

 Locking transactions may be used to atomically read-modify-write
 data anywhere in a database. This type of transaction is externally
 consistent.

 Clients should attempt to minimize the amount of time a transaction
 is active. Faster transactions commit with higher probability
 and cause less contention. Cloud Spanner attempts to keep read locks
 active as long as the transaction continues to do reads, and the
 transaction has not been terminated by
 [Commit][google.spanner.v1.Spanner.Commit] or
 [Rollback][google.spanner.v1.Spanner.Rollback]. Long periods of
 inactivity at the client may cause Cloud Spanner to release a
 transaction's locks and abort it.

 Conceptually, a read-write transaction consists of zero or more
 reads or SQL statements followed by
 [Commit][google.spanner.v1.Spanner.Commit]. At any time before
 [Commit][google.spanner.v1.Spanner.Commit], the client can send a
 [Rollback][google.spanner.v1.Spanner.Rollback] request to abort the
 transaction.

 Semantics:

 Cloud Spanner can commit the transaction if all read locks it acquired
 are still valid at commit time, and it is able to acquire write
 locks for all writes. Cloud Spanner can abort the transaction for any
 reason. If a commit attempt returns `ABORTED`, Cloud Spanner guarantees
 that the transaction has not modified any user data in Cloud Spanner.

 Unless the transaction commits, Cloud Spanner makes no guarantees about
 how long the transaction's locks were held for. It is an error to
 use Cloud Spanner locks for any sort of mutual exclusion other than
 between Cloud Spanner transactions themselves.

 Retrying aborted transactions:

 When a transaction aborts, the application can choose to retry the
 whole transaction again. To maximize the chances of successfully
 committing the retry, the client should execute the retry in the
 same session as the original attempt. The original session's lock
 priority increases with each consecutive abort, meaning that each
 attempt has a slightly better chance of success than the previous.

 Under some circumstances (for example, many transactions attempting to
 modify the same row(s)), a transaction can abort many times in a
 short period before successfully committing. Thus, it is not a good
 idea to cap the number of retries a transaction can attempt;
 instead, it is better to limit the total amount of time spent
 retrying.

 Idle transactions:

 A transaction is considered idle if it has no outstanding reads or
 SQL queries and has not started a read or SQL query within the last 10
 seconds. Idle transactions can be aborted by Cloud Spanner so that they
 don't hold on to locks indefinitely. If an idle transaction is aborted, the
 commit will fail with error `ABORTED`.

 If this behavior is undesirable, periodically executing a simple
 SQL query in the transaction (for example, `SELECT 1`) prevents the
 transaction from becoming idle.

 Snapshot read-only transactions:

 Snapshot read-only transactions provides a simpler method than
 locking read-write transactions for doing several consistent
 reads. However, this type of transaction does not support writes.

 Snapshot transactions do not take locks. Instead, they work by
 choosing a Cloud Spanner timestamp, then executing all reads at that
 timestamp. Since they do not acquire locks, they do not block
 concurrent read-write transactions.

 Unlike locking read-write transactions, snapshot read-only
 transactions never abort. They can fail if the chosen read
 timestamp is garbage collected; however, the default garbage
 collection policy is generous enough that most applications do not
 need to worry about this in practice.

 Snapshot read-only transactions do not need to call
 [Commit][google.spanner.v1.Spanner.Commit] or
 [Rollback][google.spanner.v1.Spanner.Rollback] (and in fact are not
 permitted to do so).

 To execute a snapshot transaction, the client specifies a timestamp
 bound, which tells Cloud Spanner how to choose a read timestamp.

 The types of timestamp bound are:

   - Strong (the default).
   - Bounded staleness.
   - Exact staleness.

 If the Cloud Spanner database to be read is geographically distributed,
 stale read-only transactions can execute more quickly than strong
 or read-write transactions, because they are able to execute far
 from the leader replica.

 Each type of timestamp bound is discussed in detail below.

 Strong: Strong reads are guaranteed to see the effects of all transactions
 that have committed before the start of the read. Furthermore, all
 rows yielded by a single read are consistent with each other -- if
 any part of the read observes a transaction, all parts of the read
 see the transaction.

 Strong reads are not repeatable: two consecutive strong read-only
 transactions might return inconsistent results if there are
 concurrent writes. If consistency across reads is required, the
 reads should be executed within a transaction or at an exact read
 timestamp.

 Queries on change streams (see below for more details) must also specify
 the strong read timestamp bound.

 See
 [TransactionOptions.ReadOnly.strong][google.spanner.v1.TransactionOptions.ReadOnly.strong].

 Exact staleness:

 These timestamp bounds execute reads at a user-specified
 timestamp. Reads at a timestamp are guaranteed to see a consistent
 prefix of the global transaction history: they observe
 modifications done by all transactions with a commit timestamp less than or
 equal to the read timestamp, and observe none of the modifications done by
 transactions with a larger commit timestamp. They will block until
 all conflicting transactions that may be assigned commit timestamps
 <= the read timestamp have finished.

 The timestamp can either be expressed as an absolute Cloud Spanner commit
 timestamp or a staleness relative to the current time.

 These modes do not require a "negotiation phase" to pick a
 timestamp. As a result, they execute slightly faster than the
 equivalent boundedly stale concurrency modes. On the other hand,
 boundedly stale reads usually return fresher results.

 See
 [TransactionOptions.ReadOnly.read_timestamp][google.spanner.v1.TransactionOptions.ReadOnly.read_timestamp]
 and
 [TransactionOptions.ReadOnly.exact_staleness][google.spanner.v1.TransactionOptions.ReadOnly.exact_staleness].

 Bounded staleness:

 Bounded staleness modes allow Cloud Spanner to pick the read timestamp,
 subject to a user-provided staleness bound. Cloud Spanner chooses the
 newest timestamp within the staleness bound that allows execution
 of the reads at the closest available replica without blocking.

 All rows yielded are consistent with each other -- if any part of
 the read observes a transaction, all parts of the read see the
 transaction. Boundedly stale reads are not repeatable: two stale
 reads, even if they use the same staleness bound, can execute at
 different timestamps and thus return inconsistent results.

 Boundedly stale reads execute in two phases: the first phase
 negotiates a timestamp among all replicas needed to serve the
 read. In the second phase, reads are executed at the negotiated
 timestamp.

 As a result of the two phase execution, bounded staleness reads are
 usually a little slower than comparable exact staleness
 reads. However, they are typically able to return fresher
 results, and are more likely to execute at the closest replica.

 Because the timestamp negotiation requires up-front knowledge of
 which rows will be read, it can only be used with single-use
 read-only transactions.

 See
 [TransactionOptions.ReadOnly.max_staleness][google.spanner.v1.TransactionOptions.ReadOnly.max_staleness]
 and
 [TransactionOptions.ReadOnly.min_read_timestamp][google.spanner.v1.TransactionOptions.ReadOnly.min_read_timestamp].

 Old read timestamps and garbage collection:

 Cloud Spanner continuously garbage collects deleted and overwritten data
 in the background to reclaim storage space. This process is known
 as "version GC". By default, version GC reclaims versions after they
 are one hour old. Because of this, Cloud Spanner cannot perform reads
 at read timestamps more than one hour in the past. This
 restriction also applies to in-progress reads and/or SQL queries whose
 timestamp become too old while executing. Reads and SQL queries with
 too-old read timestamps fail with the error `FAILED_PRECONDITION`.

 You can configure and extend the `VERSION_RETENTION_PERIOD` of a
 database up to a period as long as one week, which allows Cloud Spanner
 to perform reads up to one week in the past.

 Querying change Streams:

 A Change Stream is a schema object that can be configured to watch data
 changes on the entire database, a set of tables, or a set of columns
 in a database.

 When a change stream is created, Spanner automatically defines a
 corresponding SQL Table-Valued Function (TVF) that can be used to query
 the change records in the associated change stream using the
 ExecuteStreamingSql API. The name of the TVF for a change stream is
 generated from the name of the change stream: READ_<change_stream_name>.

 All queries on change stream TVFs must be executed using the
 ExecuteStreamingSql API with a single-use read-only transaction with a
 strong read-only timestamp_bound. The change stream TVF allows users to
 specify the start_timestamp and end_timestamp for the time range of
 interest. All change records within the retention period is accessible
 using the strong read-only timestamp_bound. All other TransactionOptions
 are invalid for change stream queries.

 In addition, if TransactionOptions.read_only.return_read_timestamp is set
 to true, a special value of 2^63 - 2 will be returned in the
 [Transaction][google.spanner.v1.Transaction] message that describes the
 transaction, instead of a valid read timestamp. This special value should be
 discarded and not used for any subsequent queries.

 Please see https://cloud.google.com/spanner/docs/change-streams
 for more details on how to query the change stream TVFs.

 Partitioned DML transactions:

 Partitioned DML transactions are used to execute DML statements with a
 different execution strategy that provides different, and often better,
 scalability properties for large, table-wide operations than DML in a
 ReadWrite transaction. Smaller scoped statements, such as an OLTP workload,
 should prefer using ReadWrite transactions.

 Partitioned DML partitions the keyspace and runs the DML statement on each
 partition in separate, internal transactions. These transactions commit
 automatically when complete, and run independently from one another.

 To reduce lock contention, this execution strategy only acquires read locks
 on rows that match the WHERE clause of the statement. Additionally, the
 smaller per-partition transactions hold locks for less time.

 That said, Partitioned DML is not a drop-in replacement for standard DML used
 in ReadWrite transactions.

  - The DML statement must be fully-partitionable. Specifically, the statement
    must be expressible as the union of many statements which each access only
    a single row of the table.

  - The statement is not applied atomically to all rows of the table. Rather,
    the statement is applied atomically to partitions of the table, in
    independent transactions. Secondary index rows are updated atomically
    with the base table rows.

  - Partitioned DML does not guarantee exactly-once execution semantics
    against a partition. The statement will be applied at least once to each
    partition. It is strongly recommended that the DML statement should be
    idempotent to avoid unexpected results. For instance, it is potentially
    dangerous to run a statement such as
    `UPDATE table SET column = column + 1` as it could be run multiple times
    against some rows.

  - The partitions are committed automatically - there is no support for
    Commit or Rollback. If the call returns an error, or if the client issuing
    the ExecuteSql call dies, it is possible that some rows had the statement
    executed on them successfully. It is also possible that statement was
    never executed against other rows.

  - Partitioned DML transactions may only contain the execution of a single
    DML statement via ExecuteSql or ExecuteStreamingSql.

  - If any error is encountered during the execution of the partitioned DML
    operation (for instance, a UNIQUE INDEX violation, division by zero, or a
    value that cannot be stored due to schema constraints), then the
    operation is stopped at that point and an error is returned. It is
    possible that at this point, some partitions have been committed (or even
    committed multiple times), and other partitions have not been run at all.

 Given the above, Partitioned DML is good fit for large, database-wide,
 operations that are idempotent, such as deleting old rows from a very large
 table.
    Protobuf type google.spanner.v1.TransactionOptions
    See Also:
    Serialized Form

    • Field Detail

      • READ_WRITE_FIELD_NUMBER

        public static final int READ_WRITE_FIELD_NUMBER
        See Also:
        Constant Field Values

      • PARTITIONED_DML_FIELD_NUMBER

        public static final int PARTITIONED_DML_FIELD_NUMBER
        See Also:
        Constant Field Values

    • Method Detail

      • newInstance

        protected Object newInstance​(com.google.protobuf.GeneratedMessageV3.UnusedPrivateParameter unused)
        Overrides:
        newInstance in class com.google.protobuf.GeneratedMessageV3

      • getDescriptor

        public static final com.google.protobuf.Descriptors.Descriptor getDescriptor()

      • internalGetFieldAccessorTable

        protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable internalGetFieldAccessorTable()
        Specified by:
        internalGetFieldAccessorTable in class com.google.protobuf.GeneratedMessageV3

      • hasReadWrite

        public boolean hasReadWrite()
         Transaction may write.

 Authorization to begin a read-write transaction requires
 `spanner.databases.beginOrRollbackReadWriteTransaction` permission
 on the `session` resource.
        .google.spanner.v1.TransactionOptions.ReadWrite read_write = 1;
        Specified by:
        hasReadWrite in interface TransactionOptionsOrBuilder
        Returns:
        Whether the readWrite field is set.

      • getReadWrite

        public TransactionOptions.ReadWrite getReadWrite()
         Transaction may write.

 Authorization to begin a read-write transaction requires
 `spanner.databases.beginOrRollbackReadWriteTransaction` permission
 on the `session` resource.
        .google.spanner.v1.TransactionOptions.ReadWrite read_write = 1;
        Specified by:
        getReadWrite in interface TransactionOptionsOrBuilder
        Returns:
        The readWrite.

      • hasPartitionedDml

        public boolean hasPartitionedDml()
         Partitioned DML transaction.

 Authorization to begin a Partitioned DML transaction requires
 `spanner.databases.beginPartitionedDmlTransaction` permission
 on the `session` resource.
        .google.spanner.v1.TransactionOptions.PartitionedDml partitioned_dml = 3;
        Specified by:
        hasPartitionedDml in interface TransactionOptionsOrBuilder
        Returns:
        Whether the partitionedDml field is set.

      • getPartitionedDml

        public TransactionOptions.PartitionedDml getPartitionedDml()
         Partitioned DML transaction.

 Authorization to begin a Partitioned DML transaction requires
 `spanner.databases.beginPartitionedDmlTransaction` permission
 on the `session` resource.
        .google.spanner.v1.TransactionOptions.PartitionedDml partitioned_dml = 3;
        Specified by:
        getPartitionedDml in interface TransactionOptionsOrBuilder
        Returns:
        The partitionedDml.

      • hasReadOnly

        public boolean hasReadOnly()
         Transaction will not write.

 Authorization to begin a read-only transaction requires
 `spanner.databases.beginReadOnlyTransaction` permission
 on the `session` resource.
        .google.spanner.v1.TransactionOptions.ReadOnly read_only = 2;
        Specified by:
        hasReadOnly in interface TransactionOptionsOrBuilder
        Returns:
        Whether the readOnly field is set.

      • getReadOnly

        public TransactionOptions.ReadOnly getReadOnly()
         Transaction will not write.

 Authorization to begin a read-only transaction requires
 `spanner.databases.beginReadOnlyTransaction` permission
 on the `session` resource.
        .google.spanner.v1.TransactionOptions.ReadOnly read_only = 2;
        Specified by:
        getReadOnly in interface TransactionOptionsOrBuilder
        Returns:
        The readOnly.

      • isInitialized

        public final boolean isInitialized()
        Specified by:
        isInitialized in interface com.google.protobuf.MessageLiteOrBuilder
        Overrides:
        isInitialized in class com.google.protobuf.GeneratedMessageV3

      • writeTo

        public void writeTo​(com.google.protobuf.CodedOutputStream output)
             throws IOException
        Specified by:
        writeTo in interface com.google.protobuf.MessageLite
        Overrides:
        writeTo in class com.google.protobuf.GeneratedMessageV3
        Throws:
        IOException

      • getSerializedSize

        public int getSerializedSize()
        Specified by:
        getSerializedSize in interface com.google.protobuf.MessageLite
        Overrides:
        getSerializedSize in class com.google.protobuf.GeneratedMessageV3

      • equals

        public boolean equals​(Object obj)
        Specified by:
        equals in interface com.google.protobuf.Message
        Overrides:
        equals in class com.google.protobuf.AbstractMessage

      • hashCode

        public int hashCode()
        Specified by:
        hashCode in interface com.google.protobuf.Message
        Overrides:
        hashCode in class com.google.protobuf.AbstractMessage

      • parseFrom

        public static TransactionOptions parseFrom​(ByteBuffer data)
                                    throws com.google.protobuf.InvalidProtocolBufferException
        Throws:
        com.google.protobuf.InvalidProtocolBufferException

      • parseFrom

        public static TransactionOptions parseFrom​(ByteBuffer data,
                                           com.google.protobuf.ExtensionRegistryLite extensionRegistry)
                                    throws com.google.protobuf.InvalidProtocolBufferException
        Throws:
        com.google.protobuf.InvalidProtocolBufferException

      • parseFrom

        public static TransactionOptions parseFrom​(com.google.protobuf.ByteString data)
                                    throws com.google.protobuf.InvalidProtocolBufferException
        Throws:
        com.google.protobuf.InvalidProtocolBufferException

      • parseFrom

        public static TransactionOptions parseFrom​(com.google.protobuf.ByteString data,
                                           com.google.protobuf.ExtensionRegistryLite extensionRegistry)
                                    throws com.google.protobuf.InvalidProtocolBufferException
        Throws:
        com.google.protobuf.InvalidProtocolBufferException

      • parseFrom

        public static TransactionOptions parseFrom​(byte[] data)
                                    throws com.google.protobuf.InvalidProtocolBufferException
        Throws:
        com.google.protobuf.InvalidProtocolBufferException

      • parseFrom

        public static TransactionOptions parseFrom​(byte[] data,
                                           com.google.protobuf.ExtensionRegistryLite extensionRegistry)
                                    throws com.google.protobuf.InvalidProtocolBufferException
        Throws:
        com.google.protobuf.InvalidProtocolBufferException

      • parseFrom

        public static TransactionOptions parseFrom​(com.google.protobuf.CodedInputStream input,
                                           com.google.protobuf.ExtensionRegistryLite extensionRegistry)
                                    throws IOException
        Throws:
        IOException

      • newBuilderForType

        public TransactionOptions.Builder newBuilderForType()
        Specified by:
        newBuilderForType in interface com.google.protobuf.Message
        Specified by:
        newBuilderForType in interface com.google.protobuf.MessageLite

      • toBuilder

        public TransactionOptions.Builder toBuilder()
        Specified by:
        toBuilder in interface com.google.protobuf.Message
        Specified by:
        toBuilder in interface com.google.protobuf.MessageLite

      • newBuilderForType

        protected TransactionOptions.Builder newBuilderForType​(com.google.protobuf.GeneratedMessageV3.BuilderParent parent)
        Specified by:
        newBuilderForType in class com.google.protobuf.GeneratedMessageV3

      • getParserForType

        public com.google.protobuf.Parser<TransactionOptions> getParserForType()
        Specified by:
        getParserForType in interface com.google.protobuf.Message
        Specified by:
        getParserForType in interface com.google.protobuf.MessageLite
        Overrides:
        getParserForType in class com.google.protobuf.GeneratedMessageV3

      • getDefaultInstanceForType

        public TransactionOptions getDefaultInstanceForType()
        Specified by:
        getDefaultInstanceForType in interface com.google.protobuf.MessageLiteOrBuilder
        Specified by:
        getDefaultInstanceForType in interface com.google.protobuf.MessageOrBuilder