public interface Session extends DatabaseClient, AutoCloseable
A Session
can be used to perform transactions that read and/or modify data in a Cloud
Spanner database.
Sessions can only execute one transaction at a time. To execute multiple concurrent read-write/write-only transactions, create multiple sessions. Note that standalone reads and queries use a transaction internally, and count toward the one transaction limit.
Cloud Spanner limits the number of sessions that can exist at any given time; thus, it is a good idea to delete idle and/or unneeded sessions. Aside from explicit deletes, Cloud Spanner can delete sessions for which no operations are sent for more than an hour, or due to internal errors. If a session is deleted, requests to it return ErrorCode#NOT_FOUND.
Idle sessions can be kept alive by sending a trivial SQL query periodically, for example,
SELECT 1
.
Sessions are long-lived objects intended to be reused for many consecutive operations; a typical application will maintain a pool of sessions to use during its lifetime.
Since only one transaction can be performed at a time within any given session, instances
require external synchronization; Session
implementations are not required to be
thread-safe.
Methods
asyncClose()
public abstract ApiFuture<Empty> asyncClose()
Closes the session asynchronously and returns the ApiFuture that can be used to monitor the operation progress.
Returns | |
---|---|
Type | Description |
ApiFuture<Empty> |
close()
public abstract void close()
getName()
public abstract String getName()
Returns the resource name associated with this session.
Returns | |
---|---|
Type | Description |
String |
prepareReadWriteTransaction()
public abstract void prepareReadWriteTransaction()
Prepares a transaction for use by a subsequent #readWriteTransaction() or #write(Iterable) call. It is not necessary to call this method before running a transaction or performing a write, but doing so may allow one round trip of the protocol to be performed in advance; calling this method on an idle session that is expected to execute a transaction or write in the near future may reduce the latency of the subsequent transaction/write.