CachingRelMetadataProvider (Apache Calcite API)

java.lang.Object
- org.apache.calcite.rel.metadata.CachingRelMetadataProvider

All Implemented Interfaces:

RelMetadataProvider
```
public class CachingRelMetadataProvider
extends java.lang.Object
implements RelMetadataProvider
```
Implementation of the RelMetadataProvider interface that caches results from an underlying provider.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`private static class`	`CachingRelMetadataProvider.CacheEntry`	An entry in the cache.
`private class`	`CachingRelMetadataProvider.CachingInvocationHandler`	Implementation of `InvocationHandler` for calls to a `CachingRelMetadataProvider`.

Field Summary

Fields
Modifier and Type	Field	Description
`private java.util.Map<java.util.List,CachingRelMetadataProvider.CacheEntry>`	`cache`
`private RelOptPlanner`	`planner`
`private RelMetadataProvider`	`underlyingProvider`

Constructor Summary

Constructors
Constructor Description

CachingRelMetadataProvider(RelMetadataProvider underlyingProvider, RelOptPlanner planner)

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`<M extends Metadata> UnboundMetadata<M>`	`apply(java.lang.Class<? extends RelNode> relClass, java.lang.Class<? extends M> metadataClass)`	Retrieves metadata of a particular type and for a particular sub-class of relational expression.
`<M extends Metadata> com.google.common.collect.Multimap<java.lang.reflect.Method,MetadataHandler<M>>`	`handlers(MetadataDef<M> def)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

cache

private final java.util.Map<java.util.List,CachingRelMetadataProvider.CacheEntry> cache

underlyingProvider

private final RelMetadataProvider underlyingProvider

planner
```
private final RelOptPlanner planner
```

Constructor Detail

CachingRelMetadataProvider

public CachingRelMetadataProvider(RelMetadataProvider underlyingProvider,
                                  RelOptPlanner planner)

Method Detail
- apply
```
public <M extends Metadata> UnboundMetadata<M> apply(java.lang.Class<? extends RelNode> relClass,
                                                     java.lang.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<java.lang.reflect.Method,MetadataHandler<M>> handlers(MetadataDef<M> def)
```
  Specified by:
  
  handlers in interface RelMetadataProvider