Package org.apache.druid.query.groupby

Class GroupByQueryResources

java.lang.Object

org.apache.druid.query.groupby.GroupByQueryResources

All Implemented Interfaces:

Closeable, AutoCloseable

public class GroupByQueryResources
extends Object
implements Closeable

This class contains resources required for a groupBy query execution. Currently, it contains only merge buffers, but any additional resources can be added in the future. It contains merge buffers for the execution of a) GroupByQueryQueryToolChest.mergeResults(QueryRunner) - Required for merging the results of the subqueries and the subtotals. b) GroupByMergingQueryRunner - Required for merging the results of the individual runners created by GroupByQueryRunnerFactory.createRunner(Segment) The resources should be acquired once throughout the execution of the query (with caveats such as union being treated as separate queries on the data servers) or it should release all the resources before re-acquiring them (if needed), to prevent deadlocks.

Constructor Summary

Constructors

Constructor	Description
GroupByQueryResources(List<ReferenceCountingResourceHolder<ByteBuffer>> toolchestMergeBuffersHolders, List<ReferenceCountingResourceHolder<ByteBuffer>> mergingQueryRunnerMergeBuffersHolders)

Method Summary

Modifier and Type	Method	Description
void	close()	Closes the query resource.
static int	countRequiredMergeBufferNumForMergingQueryRunner(GroupByQueryConfig config, GroupByQuery query)	Count the number of merge buffers required for GroupByMergingQueryRunner It can be either 1 or 2, depending on the query's config
static int	countRequiredMergeBufferNumForToolchestMerge(GroupByQuery query)	Counts the number of merge buffers required for GroupByQueryQueryToolChest.mergeResults(org.apache.druid.query.QueryRunner<org.apache.druid.query.groupby.ResultRow>).
ResourceHolder<ByteBuffer>	getMergingQueryRunnerMergeBuffer()	Returns a merge buffer associated with the GroupByMergingQueryRunner
int	getNumMergingQueryRunnerMergeBuffers()	Returns the number of the currently unused merge buffers reserved for GroupByMergingQueryRunner
ResourceHolder<ByteBuffer>	getToolchestMergeBuffer()	Returns a merge buffer associate with the GroupByQueryQueryToolChest.mergeResults(org.apache.druid.query.QueryRunner<org.apache.druid.query.groupby.ResultRow>)

Methods inherited from class java.lang.Object

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

Constructor Details

GroupByQueryResources

public GroupByQueryResources(@Nullable
 List<ReferenceCountingResourceHolder<ByteBuffer>> toolchestMergeBuffersHolders,
 @Nullable
 List<ReferenceCountingResourceHolder<ByteBuffer>> mergingQueryRunnerMergeBuffersHolders)

Method Details

countRequiredMergeBufferNumForToolchestMerge

public static int countRequiredMergeBufferNumForToolchestMerge(GroupByQuery query)

Counts the number of merge buffers required for GroupByQueryQueryToolChest.mergeResults(org.apache.druid.query.QueryRunner<org.apache.druid.query.groupby.ResultRow>). For a given query, it is dependent on the structure of the group by query.

countRequiredMergeBufferNumForMergingQueryRunner

public static int countRequiredMergeBufferNumForMergingQueryRunner(GroupByQueryConfig config,
 GroupByQuery query)

Count the number of merge buffers required for GroupByMergingQueryRunner It can be either 1 or 2, depending on the query's config

getToolchestMergeBuffer

public ResourceHolder<ByteBuffer> getToolchestMergeBuffer()

Returns a merge buffer associate with the GroupByQueryQueryToolChest.mergeResults(org.apache.druid.query.QueryRunner<org.apache.druid.query.groupby.ResultRow>)

getMergingQueryRunnerMergeBuffer

public ResourceHolder<ByteBuffer> getMergingQueryRunnerMergeBuffer()

Returns a merge buffer associated with the GroupByMergingQueryRunner

getNumMergingQueryRunnerMergeBuffers

public int getNumMergingQueryRunnerMergeBuffers()

Returns the number of the currently unused merge buffers reserved for GroupByMergingQueryRunner

close

public void close()

Closes the query resource. It must be called to release back the acquired merge buffers back into the global merging pool from where all the merge buffers are acquired. The references to the merge buffers will become invalid once this method is called. The user must ensure that the callers are not using the stale references to the merge buffers after this method is called, as reading them would give incorrect results and writing there would interfere with other users of the merge buffers

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable