public interface TransactionRunnerAn interface for executing a body of work in the context of a read-write transaction, with
retries for transaction aborts. See 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).
Methods
<T>run(TransactionRunner.TransactionCallable<T> callable)
public abstract T <T>run(TransactionRunner.TransactionCallable<T> callable)Executes a read-write transaction, with retries as necessary. The work to perform in each
transaction attempt is defined by callable, 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 by callable will only
be applied if the transaction commits successfully. Similarly, the value produced by
callable 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 execute callable, and the exception will propagate from this method call.
However, if a read or query in callable detected that the transaction aborted,
callable will be retried even if it raised an exception.
| Parameter | |
|---|---|
| Name | Description |
callable | TransactionCallable<T> |
| Returns | |
|---|---|
| Type | Description |
T | |
allowNestedTransaction()
public abstract 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 | |
|---|---|
| Type | Description |
TransactionRunner | this object |
getCommitResponse()
public abstract CommitResponse getCommitResponse()Returns the CommitResponse of this transaction.
| Returns | |
|---|---|
| Type | Description |
CommitResponse | |
getCommitTimestamp()
public abstract Timestamp getCommitTimestamp()Returns the timestamp at which the transaction committed. This method may only be called once #run(TransactionCallable) has returned normally.
| Returns | |
|---|---|
| Type | Description |
com.google.cloud.Timestamp | |