org.apache.calcite.rel.metadata

Class ChainedRelMetadataProvider

java.lang.Object

org.apache.calcite.rel.metadata.ChainedRelMetadataProvider

All Implemented Interfaces:

RelMetadataProvider

Direct Known Subclasses:

DefaultRelMetadataProvider

public class ChainedRelMetadataProvider
extends Object
implements RelMetadataProvider

Implementation of the RelMetadataProvider interface via the Glossary.CHAIN_OF_RESPONSIBILITY_PATTERN.

When a consumer calls the apply(java.lang.Class<? extends org.apache.calcite.rel.RelNode>, java.lang.Class<? extends org.apache.calcite.rel.metadata.Metadata>) method to ask for a provider for a particular type of RelNode and Metadata, scans the list of underlying providers.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ChainedRelMetadataProvider(com.google.common.collect.ImmutableList<RelMetadataProvider> providers) Creates a chain.

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.
static RelMetadataProvider	of(List<RelMetadataProvider> list) Creates a chain.

Methods inherited from class java.lang.Object

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

Constructor Detail

ChainedRelMetadataProvider

protected ChainedRelMetadataProvider(com.google.common.collect.ImmutableList<RelMetadataProvider> providers)

Creates a chain.

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

of

public static RelMetadataProvider of(List<RelMetadataProvider> list)

Creates a chain.