Package org.apache.druid.query

Class ChainedExecutionQueryRunner<T>

java.lang.Object

org.apache.druid.query.ChainedExecutionQueryRunner<T>

All Implemented Interfaces:

QueryRunner<T>

public class ChainedExecutionQueryRunner<T>
extends Object
implements QueryRunner<T>

A QueryRunner that combines a list of other QueryRunners and executes them in parallel on an executor.

When using this, it is important to make sure that the list of QueryRunners provided is fully flattened. If, for example, you were to pass a list of a Chained QueryRunner (A) and a non-chained QueryRunner (B). Imagine A has 2 QueryRunner chained together (Aa and Ab), the fact that the Queryables are run in parallel on an executor would mean that the Queryables are actually processed in the order

A -> B -> Aa -> Ab

That is, the two sub queryables for A would run *after* B is run, effectively meaning that the results for B must be fully cached in memory before the results for Aa and Ab are computed.

Constructor Summary

Constructors

Constructor	Description
ChainedExecutionQueryRunner(QueryProcessingPool queryProcessingPool, QueryWatcher queryWatcher, Iterable<QueryRunner<T>> queryables)

Method Summary

Modifier and Type	Method	Description
Sequence<T>	run(QueryPlus<T> queryPlus, ResponseContext responseContext)	Runs the given query and returns results in a time-ordered sequence.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.druid.query.QueryRunner

run

Constructor Detail

ChainedExecutionQueryRunner

public ChainedExecutionQueryRunner(QueryProcessingPool queryProcessingPool,
                                   QueryWatcher queryWatcher,
                                   Iterable<QueryRunner<T>> queryables)

Method Detail

run

public Sequence<T> run(QueryPlus<T> queryPlus,
                       ResponseContext responseContext)

Description copied from interface: QueryRunner

Runs the given query and returns results in a time-ordered sequence.

Specified by:

run in interface QueryRunner<T>