org.apache.calcite.rel.metadata

Class RelMetadataQueryBase

java.lang.Object

org.apache.calcite.rel.metadata.RelMetadataQueryBase

Direct Known Subclasses:

RelMetadataQuery

public class RelMetadataQueryBase
extends Object

Base class for the RelMetadataQuery that uses the metadata handler class generated by the Janino.

To add a new implementation to this interface, follow these steps:

1. Extends RelMetadataQuery (name it MyRelMetadataQuery for example) to reuse the Calcite builtin metadata query interfaces. In this class, define all the extended Handlers for your metadata and implement the metadata query interfaces.
2. Write your customized provider class RelMdXyz. Follow the pattern from an existing class such as RelMdColumnOrigins, overloading on all of the logical relational expressions to which the query applies.
3. Add a SOURCE static member to each of your provider class, similar to RelMdColumnOrigins.SOURCE.
4. Extends DefaultRelMetadataProvider (name it MyRelMetadataProvider for example) and supplement the "SOURCE"s into the builtin list (This is not required, use ChainedRelMetadataProvider to chain your customized "SOURCE"s with default ones also works).
5. Set MyRelMetadataProvider into the cluster instance.
6. Use RelOptCluster.setMetadataQuerySupplier(Supplier) to set the metadata query Supplier into the cluster instance. This Supplier should return a fresh new instance.
7. Use the cluster instance to create SqlToRelConverter.
8. Query your metadata within RelOptRuleCall with the interfaces you defined in MyRelMetadataQuery.

Field Summary

Fields

Modifier and Type	Field and Description
com.google.common.collect.Table<RelNode,List,Object>	map Set of active metadata queries, and cache of previous results.
JaninoRelMetadataProvider	metadataProvider
static ThreadLocal<JaninoRelMetadataProvider>	THREAD_PROVIDERS

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	RelMetadataQueryBase(JaninoRelMetadataProvider metadataProvider)

Method Summary

Modifier and Type	Method and Description
boolean	clearCache(RelNode rel) Removes cached metadata values for specified RelNode.
protected static <H> H	initialHandler(Class<H> handlerClass)
protected <M extends Metadata,H extends MetadataHandler<M>> H	revise(Class<? extends RelNode> class_, MetadataDef<M> def) Re-generates the handler for a given kind of metadata, adding support for class_ if it is not already present.

Methods inherited from class java.lang.Object

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

Field Detail

map

public final com.google.common.collect.Table<RelNode,List,Object> map

Set of active metadata queries, and cache of previous results.

metadataProvider

public final JaninoRelMetadataProvider metadataProvider

THREAD_PROVIDERS

public static final ThreadLocal<JaninoRelMetadataProvider> THREAD_PROVIDERS

Constructor Detail

RelMetadataQueryBase

protected RelMetadataQueryBase(JaninoRelMetadataProvider metadataProvider)

Method Detail

initialHandler

protected static <H> H initialHandler(Class<H> handlerClass)

revise

protected <M extends Metadata,H extends MetadataHandler<M>> H revise(Class<? extends RelNode> class_,
                                                                     MetadataDef<M> def)

Re-generates the handler for a given kind of metadata, adding support for class_ if it is not already present.

clearCache

public boolean clearCache(RelNode rel)

Removes cached metadata values for specified RelNode.

Parameters:

rel - RelNode whose cached metadata should be removed

Returns:

true if cache for the provided RelNode was not empty