org.apache.calcite.rel.metadata

Class ReflectiveRelMetadataProvider

java.lang.Object

org.apache.calcite.rel.metadata.ReflectiveRelMetadataProvider

All Implemented Interfaces:

RelMetadataProvider, ReflectiveVisitor

public class ReflectiveRelMetadataProvider
extends Object
implements RelMetadataProvider, ReflectiveVisitor

Implementation of the RelMetadataProvider interface that dispatches metadata methods to methods on a given object via reflection.

The methods on the target object must be public and non-static, and have the same signature as the implemented metadata method except for an additional first parameter of type RelNode or a sub-class. That parameter gives this provider an indication of that relational expressions it can handle.

For an example, see RelMdColumnOrigins.SOURCE.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) static class	ReflectiveRelMetadataProvider.Space Workspace for computing which methods can act as handlers for given metadata methods.
(package private) static class	ReflectiveRelMetadataProvider.Space2 Extended work space.

Field Summary

Fields

Modifier and Type	Field and Description
private com.google.common.collect.ImmutableMultimap<Method,MetadataHandler>	handlerMap
private ConcurrentMap<Class<RelNode>,UnboundMetadata>	map
private Class<? extends Metadata>	metadataClass0

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ReflectiveRelMetadataProvider(ConcurrentMap<Class<RelNode>,UnboundMetadata> map, Class<? extends Metadata> metadataClass0, com.google.common.collect.Multimap<Method,MetadataHandler> handlerMap) Creates a ReflectiveRelMetadataProvider.

Method Summary

Modifier and Type	Method and Description
<M extends Metadata> UnboundMetadata<M>	apply(Class<? extends RelNode> relClass)
<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.
private static boolean	couldImplement(Method handlerMethod, Method method)
<M extends Metadata> com.google.common.collect.Multimap<Method,MetadataHandler<M>>	handlers(MetadataDef<M> def)
private static RelMetadataProvider	reflectiveSource(MetadataHandler target, com.google.common.collect.ImmutableList<Method> methods)
static RelMetadataProvider	reflectiveSource(MetadataHandler target, Method... methods) Returns a reflective metadata provider that implements several methods.
static RelMetadataProvider	reflectiveSource(Method method, MetadataHandler target) Returns an implementation of RelMetadataProvider that scans for methods with a preceding argument.

Methods inherited from class java.lang.Object

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

Field Detail

map

private final ConcurrentMap<Class<RelNode>,UnboundMetadata> map

metadataClass0

private final Class<? extends Metadata> metadataClass0

handlerMap

private final com.google.common.collect.ImmutableMultimap<Method,MetadataHandler> handlerMap

Constructor Detail

ReflectiveRelMetadataProvider

protected ReflectiveRelMetadataProvider(ConcurrentMap<Class<RelNode>,UnboundMetadata> map,
                                        Class<? extends Metadata> metadataClass0,
                                        com.google.common.collect.Multimap<Method,MetadataHandler> handlerMap)

Creates a ReflectiveRelMetadataProvider.

Parameters:

map - Map

metadataClass0 - Metadata class

handlerMap - Methods handled and the objects to call them on

Method Detail

reflectiveSource

public static RelMetadataProvider reflectiveSource(Method method,
                                                   MetadataHandler target)

Returns an implementation of RelMetadataProvider that scans for methods with a preceding argument.

For example, BuiltInMetadata.Selectivity has a method BuiltInMetadata.Selectivity.getSelectivity(RexNode). A class

 class RelMdSelectivity {
   public Double getSelectivity(Union rel, RexNode predicate) { }
   public Double getSelectivity(Filter rel, RexNode predicate) { }
 

provides implementations of selectivity for relational expressions that extend Union or Filter.

reflectiveSource

public static RelMetadataProvider reflectiveSource(MetadataHandler target,
                                                   Method... methods)

Returns a reflective metadata provider that implements several methods.

reflectiveSource

private static RelMetadataProvider reflectiveSource(MetadataHandler target,
                                                    com.google.common.collect.ImmutableList<Method> methods)

handlers

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

Specified by:

handlers in interface RelMetadataProvider

couldImplement

private static boolean couldImplement(Method handlerMethod,
                                      Method method)

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

apply

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