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 M>) method to ask for a provider for a particular type of RelNode and Metadata, scans the list of underlying providers.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	ChainedRelMetadataProvider.ChainedInvocationHandler Invocation handler that calls a list of Metadata objects, returning the first non-null value.

Field Summary

Fields

Modifier and Type	Field and Description
private com.google.common.collect.ImmutableList<RelMetadataProvider>	providers

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
<M extends Metadata> UnboundMetadata<M>	apply(Class<? extends RelNode> relClass, Class<? extends M> metadataClass) Retrieves metadata of a particular type and for a particular sub-class of relational expression.
boolean	equals(Object obj)
<M extends Metadata> com.google.common.collect.Multimap<Method,MetadataHandler<M>>	handlers(MetadataDef<M> def)
int	hashCode()
static RelMetadataProvider	of(List<RelMetadataProvider> list) Creates a chain.

Methods inherited from class java.lang.Object

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

Field Detail

providers

private final com.google.common.collect.ImmutableList<RelMetadataProvider> providers

Constructor Detail

ChainedRelMetadataProvider

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

Creates a chain.

Method Detail

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

apply

public <M extends Metadata> UnboundMetadata<M> apply(Class<? extends RelNode> relClass,
                                                     Class<? extends M> 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

handlers

public <M extends Metadata> com.google.common.collect.Multimap<Method,MetadataHandler<M>> handlers(MetadataDef<M> def)

Specified by:

handlers in interface RelMetadataProvider

of

public static RelMetadataProvider of(List<RelMetadataProvider> list)

Creates a chain.