Interface TransactionRunner
TransactionContext
for a description of transaction
semantics. TransactionRunner
instances are obtained by calling DatabaseClient.readWriteTransaction(TransactionOption...)
.
A TransactionRunner
instance can only be used for a single invocation of run(TransactionCallable)
.
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Nested Class Summary
Modifier and TypeInterfaceDescriptionstatic interface
A unit of work to be performed in the context of a transaction. -
Method Summary
Modifier and TypeMethodDescriptionAllows overriding the default behaviour of blocking nested transactions.Returns theCommitResponse
of this transaction.com.google.cloud.Timestamp
Returns the timestamp at which the transaction committed.<T> T
run
(TransactionRunner.TransactionCallable<T> callable) Executes a read-write transaction, with retries as necessary.
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Method Details
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run
Executes a read-write transaction, with retries as necessary. The work to perform in each transaction attempt is defined bycallable
, which may return an object as the result of the work.callable
will be retried if a transaction attempt aborts; implementations must be prepared to be called more than once. Any writes buffered bycallable
will only be applied if the transaction commits successfully. Similarly, the value produced bycallable
will only be returned by this method if the transaction commits successfully.callable
is allowed to raise an unchecked exception. Typically this prevents further attempts to executecallable
, and the exception will propagate from this method call. However, if a read or query incallable
detected that the transaction aborted,callable
will be retried even if it raised an exception. -
getCommitTimestamp
com.google.cloud.Timestamp getCommitTimestamp()Returns the timestamp at which the transaction committed. This method may only be called oncerun(TransactionCallable)
has returned normally. -
getCommitResponse
CommitResponse getCommitResponse()Returns theCommitResponse
of this transaction. -
allowNestedTransaction
TransactionRunner allowNestedTransaction()Allows overriding the default behaviour of blocking nested transactions.Note that the client library does not maintain any information regarding the nesting structure. If an outer transaction fails and an inner transaction succeeds, upon retry of the outer transaction, the inner transaction will be re-executed.
Use with care when certain that the inner transaction is idempotent. Avoid doing this when accessing the same db. There might be legitimate uses where access need to be made across DBs for instance.
E.g. of nesting that is discouraged, see
nestedReadWriteTxnThrows
nestedReadOnlyTxnThrows
,nestedBatchTxnThrows
,nestedSingleUseReadTxnThrows
- Returns:
- this object
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