org.apache.beam.sdk.io.gcp.spanner.changestreams.dao

Class ChangeStreamResultSet

java.lang.Object

org.apache.beam.sdk.io.gcp.spanner.changestreams.dao.ChangeStreamResultSet

All Implemented Interfaces:

java.lang.AutoCloseable

public class ChangeStreamResultSet
extends java.lang.Object
implements java.lang.AutoCloseable

Decorator class over a ResultSet that provides telemetry for the streamed records. It will be returned for a change stream query. By using this class one can obtain the following metadata:

• The timestamp at which the query first started.
• The timestamp at which a record streaming started.
• The timestamp at which a record streaming ended.
• The timestamp at which a record was read by the caller.
• The total time for streaming all records within the query.
• The total number of records streamed within the query.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the current change stream ResultSet.
com.google.cloud.spanner.Struct	getCurrentRowAsStruct() Returns the record at the current pointer as a Struct.
ChangeStreamResultSetMetadata	getMetadata() Returns the gathered metadata for the change stream query so far.
boolean	next() Moves the pointer to the next record in the ResultSet if there is one.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

next

public boolean next()

Moves the pointer to the next record in the ResultSet if there is one. It also gathers metrics for the next record, such as:

• If this is the first record consumed, updates the time at which the query started.
• The timestamp at which a record streaming started.
• The timestamp at which a record streaming ended.
• Increments the total time for streaming the all the records so far.
• Increments the total number of all the records streamed so far.

Returns:

true if there is another record within the result set. Returns false otherwise.

getCurrentRowAsStruct

public com.google.cloud.spanner.Struct getCurrentRowAsStruct()

Returns the record at the current pointer as a Struct. It also updates the timestamp at which the record was read.

If next() was not called or if it was called but there are no more records in the stream, null will be returned.

Returns:

a change stream record as a Struct or null

getMetadata

public ChangeStreamResultSetMetadata getMetadata()

Returns the gathered metadata for the change stream query so far.

Returns:

a ChangeStreamResultSetMetadata contained telemetry information for the query so far

close

public void close()

Closes the current change stream ResultSet. The stream will be terminated when this method is called.

This method must always be called after the consumption of the result set or when an error occurs. This makes sure there are no Session leaks and all the underlying resources are released.

Specified by:

close in interface java.lang.AutoCloseable