org.apache.druid.segment.join

Interface JoinableFactory

All Known Implementing Classes:

MapJoinableFactory

public interface JoinableFactory

Utility for creating Joinable objects.

See Also:

to register factories, to register factory types with datasource types

Method Summary

Modifier and Type	Method and Description
Optional<Joinable>	build(DataSource dataSource, JoinConditionAnalysis condition) Create a Joinable object.
default Optional<byte[]>	computeJoinCacheKey(DataSource dataSource, JoinConditionAnalysis condition) Compute the cache key for a data source participating in join operation.
boolean	isDirectlyJoinable(DataSource dataSource) Returns true if a Joinable **may** be created for a given DataSource, but is not a guarantee that build(org.apache.druid.query.DataSource, org.apache.druid.segment.join.JoinConditionAnalysis) will return a non-empty result.

Method Detail

isDirectlyJoinable

boolean isDirectlyJoinable(DataSource dataSource)

Returns true if a Joinable **may** be created for a given DataSource, but is not a guarantee that build(org.apache.druid.query.DataSource, org.apache.druid.segment.join.JoinConditionAnalysis) will return a non-empty result. Successfully building a Joinable might require specific criteria of the JoinConditionAnalysis.

build

Optional<Joinable> build(DataSource dataSource,
                         JoinConditionAnalysis condition)

Create a Joinable object. This may be an expensive operation involving loading data, creating a hash table, etc.

Parameters:

dataSource - the datasource to join on

condition - the condition to join on

Returns:

a Joinable if this datasource + condition combo is joinable; empty if not

computeJoinCacheKey

default Optional<byte[]> computeJoinCacheKey(DataSource dataSource,
                                             JoinConditionAnalysis condition)

Compute the cache key for a data source participating in join operation. This is done separately from {build(DataSource, JoinConditionAnalysis)} which can be an expensive operation and can potentially be avoided if cached results can be used.

Parameters:

dataSource - the datasource to join on

condition - the condition to join on