org.apache.calcite.rel.metadata

Class CachingRelMetadataProvider

java.lang.Object

org.apache.calcite.rel.metadata.CachingRelMetadataProvider

All Implemented Interfaces:

RelMetadataProvider

public class CachingRelMetadataProvider
extends Object
implements RelMetadataProvider

Implementation of the RelMetadataProvider interface that caches results from an underlying provider.

Constructor Summary

Constructors

Constructor and Description
CachingRelMetadataProvider(RelMetadataProvider underlyingProvider, RelOptPlanner planner)

Method Summary

Methods

Modifier and Type	Method and Description
com.google.common.base.Function<RelNode,Metadata>	apply(Class<? extends RelNode> relClass, Class<? extends Metadata> metadataClass) Retrieves metadata of a particular type and for a particular sub-class of relational expression.

Methods inherited from class java.lang.Object

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

Constructor Detail

CachingRelMetadataProvider

public CachingRelMetadataProvider(RelMetadataProvider underlyingProvider,
                          RelOptPlanner planner)

Method Detail

apply

public com.google.common.base.Function<RelNode,Metadata> apply(Class<? extends RelNode> relClass,
                                                      Class<? extends Metadata> metadataClass)

Description copied from interface: RelMetadataProvider

Retrieves metadata of a particular type and for a particular sub-class of relational expression.

The object returned is a function. It can be applied to a relational expression of the given type to create a metadata object.

For example, you might call

 RelMetadataProvider provider;
 LogicalFilter filter;
 RexNode predicate;
 Function<RelNode, Metadata> function =
   provider.apply(LogicalFilter.class, Selectivity.class};
 Selectivity selectivity = function.apply(filter);
 Double d = selectivity.selectivity(predicate);
 

Specified by:

apply in interface RelMetadataProvider

Parameters:

relClass - Type of relational expression

metadataClass - Type of metadata

Returns:

Function that will field a metadata instance; or null if this provider cannot supply metadata of this type