Package org.apache.druid.query

Class GlobalTableDataSource

  • All Implemented Interfaces:
    DataSource
    public class GlobalTableDataSource
extends TableDataSource
    TableDataSource variant for globally available 'broadcast' segments. If bound to a JoinableFactory that can create an IndexedTable using DruidBinders.joinableFactoryBinder, this allows optimal usage of segments using this DataSource type in join operations (because they are global), and so can be pushed down to historicals as a JoinDataSource, instead of requiring a subquery join using InlineDataSource to construct an IndexedTable on the fly on the broker. Because it is also a TableDataSource, when queried directly, or on the left hand side of a join, they will be treated as any normal table datasource.

    • Constructor Detail

      • GlobalTableDataSource

        public GlobalTableDataSource​(String name)

    • Method Detail

      • isGlobal

        public boolean isGlobal()
        Description copied from interface: DataSource
        Returns true if all servers have a full copy of this datasource. True for things like inline, lookup, etc, or for queries of those.

        Currently this is coupled with joinability - if this returns true then the query engine expects there exists a JoinableFactory which might build a Joinable for this datasource directly. If a subquery 'inline' join is required to join this datasource on the right hand side, then this value must be false for now.

        In the future, instead of directly using this method, the query planner and engine should consider JoinableFactory.isDirectlyJoinable(DataSource) when determining if the right hand side is directly joinable, which would allow decoupling this property from joins.

        Specified by:
        isGlobal in interface DataSource
        Overrides:
        isGlobal in class TableDataSource

      • isCacheable

        public boolean isCacheable​(boolean isBroker)
        Query results from Broadcast datasources should not be cached on broker https://github.com/apache/druid/issues/10444
        Specified by:
        isCacheable in interface DataSource
        Overrides:
        isCacheable in class TableDataSource