org.apache.drill

Class SingleRowListener

java.lang.Object

org.apache.drill.SingleRowListener

All Implemented Interfaces:

UserResultsListener

public abstract class SingleRowListener
extends Object
implements UserResultsListener

Result listener that is set up to receive a single row. Useful for queries such with a count(*) or limit 1. The abstract method rowArrived(QueryDataBatch) provides the means for a derived class to get the expected record's data.

Constructor Summary

Constructors

Constructor and Description
SingleRowListener()

Method Summary

Modifier and Type	Method and Description
void	cleanup() Clean up any resources used.
void	dataArrived(QueryDataBatch result, ConnectionThrottle throttle) A QueryData message was received
List<UserBitShared.DrillPBError>	getErrorList() Get an immutable copy of the list of all errors received so far.
UserBitShared.QueryResult.QueryState	getQueryState() Get the last known QueryState.
void	queryCompleted(UserBitShared.QueryResult.QueryState state) The query has completed (successful completion or cancellation).
void	queryIdArrived(UserBitShared.QueryId queryId) QueryId is available.
protected abstract void	rowArrived(QueryDataBatch queryDataBatch) A record has arrived and is ready for access.
void	submissionFailed(UserException ex) The query has failed.
void	waitForCompletion() Wait for the completion of this query; receiving a record or an error will both cause the query to be considered complete

Methods inherited from class java.lang.Object

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

Constructor Detail

SingleRowListener

public SingleRowListener()

Method Detail

queryIdArrived

public void queryIdArrived(UserBitShared.QueryId queryId)

Description copied from interface: UserResultsListener

QueryId is available. Called when a query is successfully submitted to the server.

Specified by:

queryIdArrived in interface UserResultsListener

Parameters:

queryId - sent by the server along Acks.OK

submissionFailed

public void submissionFailed(UserException ex)

Description copied from interface: UserResultsListener

The query has failed. Most likely called when the server returns a FAILED query state. Can also be called if dataArrived() throws an exception

Specified by:

submissionFailed in interface UserResultsListener

Parameters:

ex - exception describing the cause of the failure

queryCompleted

public void queryCompleted(UserBitShared.QueryResult.QueryState state)

Description copied from interface: UserResultsListener

The query has completed (successful completion or cancellation). The listener will not receive any other data or result message. Called when the server returns a terminal-non failing- state (COMPLETED or CANCELLED)

Specified by:

queryCompleted in interface UserResultsListener

dataArrived

public void dataArrived(QueryDataBatch result,
                        ConnectionThrottle throttle)

Description copied from interface: UserResultsListener

A QueryData message was received

Specified by:

dataArrived in interface UserResultsListener

Parameters:

result - data batch received

throttle - connection throttle

getQueryState

public UserBitShared.QueryResult.QueryState getQueryState()

Get the last known QueryState.

Returns:

the query state; may be null if no query state has been received

getErrorList

public List<UserBitShared.DrillPBError> getErrorList()

Get an immutable copy of the list of all errors received so far.

Returns:

list of errors received

rowArrived

protected abstract void rowArrived(QueryDataBatch queryDataBatch)

A record has arrived and is ready for access.

Derived classes provide whatever implementation they require here to access the record's data.

Parameters:

queryDataBatch - result batch holding the row

waitForCompletion

public void waitForCompletion()
                       throws Exception

Wait for the completion of this query; receiving a record or an error will both cause the query to be considered complete

Throws:

Exception - if there was any kind of problem

cleanup

public void cleanup()

Clean up any resources used.

Derived classes may use this to free things like allocators or files that were used to record data received in resultArrived().