org.apache.druid.segment.join

Class JoinableFactoryWrapper

java.lang.Object

org.apache.druid.segment.join.JoinableFactoryWrapper

public class JoinableFactoryWrapper
extends Object

A wrapper class over JoinableFactory for working with Joinable related classes.

Constructor Summary

Constructors

Constructor and Description
JoinableFactoryWrapper(JoinableFactory joinableFactory)

Method Summary

Modifier and Type	Method and Description
Optional<byte[]>	computeJoinDataSourceCacheKey(DataSourceAnalysis dataSourceAnalysis) Compute a cache key prefix for a join data source.
Function<SegmentReference,SegmentReference>	createSegmentMapFn(Filter baseFilter, List<PreJoinableClause> clauses, AtomicLong cpuTimeAccumulator, Query<?> query) Creates a Function that maps base segments to HashJoinSegment if needed (i.e.

Methods inherited from class java.lang.Object

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

Constructor Detail

JoinableFactoryWrapper

public JoinableFactoryWrapper(JoinableFactory joinableFactory)

Method Detail

createSegmentMapFn

public Function<SegmentReference,SegmentReference> createSegmentMapFn(@Nullable
                                                                      Filter baseFilter,
                                                                      List<PreJoinableClause> clauses,
                                                                      AtomicLong cpuTimeAccumulator,
                                                                      Query<?> query)

Creates a Function that maps base segments to HashJoinSegment if needed (i.e. if the number of join clauses is > 0). If mapping is not needed, this method will return Function.identity().

Parameters:

baseFilter - Filter to apply before the join takes place

clauses - Pre-joinable clauses

cpuTimeAccumulator - An accumulator that we will add CPU nanos to; this is part of the function to encourage callers to remember to track metrics on CPU time required for creation of Joinables

query - The query that will be run on the mapped segments. Usually this should be analysis.getBaseQuery().orElse(query), where "analysis" is a DataSourceAnalysis and "query" is the original query from the end user.

computeJoinDataSourceCacheKey

public Optional<byte[]> computeJoinDataSourceCacheKey(DataSourceAnalysis dataSourceAnalysis)

Compute a cache key prefix for a join data source. This includes the data sources that participate in the RHS of a join as well as any query specific constructs associated with join data source such as base table filter. This key prefix can be used in segment level cache or result level cache. The function can return following wrapped in an Optional - Non-empty byte array - If there is join datasource involved and caching is possible. The result includes join condition expression, join type and cache key returned by joinable factory for each PreJoinableClause - NULL - There is a join but caching is not possible. It may happen if one of the participating datasource in the JOIN is not cacheable.

Parameters:

dataSourceAnalysis - for the join datasource

Returns:

the optional cache key to be used as part of query cache key

Throws:

{@link - IAE} if this operation is called on a non-join data source