Class ReadWrite (3.53.0)

ReadWrite(mapping=None, *, ignore_unknown_fields=False, **kwargs)

Message type to initiate a read-write transaction. Currently this transaction type has no options.

Attributes
Name	Description
`read_lock_mode`	`google.cloud.spanner_v1.types.TransactionOptions.ReadWrite.ReadLockMode` Read lock mode for the transaction.
`multiplexed_session_previous_transaction_id`	`bytes` 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. This feature is not yet supported and will result in an UNIMPLEMENTED error.

Classes

ReadLockMode

ReadLockMode(value)

ReadLockMode is used to set the read lock mode for read-write transactions.

    -  If isolation level is `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 for:

       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 to validate that
          the data that was served at the snapshot time is
          unchanged at commit time.

    -  At all other isolation levels, if `read_lock_mode` is
       the default value, then pessimistic read lock is used.
PESSIMISTIC (1):
    Pessimistic lock mode.

    Read locks are acquired immediately on read. Semantics
    described only applies to `SERIALIZABLE` isolation.
OPTIMISTIC (2):
    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` isolation.

Class ReadWrite (3.53.0)

Attributes

Classes

ReadLockMode