Package org.apache.calcite.rel.metadata

Interface MetadataHandlerProvider

All Known Implementing Classes:

JaninoRelMetadataProvider, ProxyingMetadataHandlerProvider

public interface MetadataHandlerProvider

Provides MetadataHandler call sites for RelMetadataQuery. The handlers provided are responsible for updating the cache stored in RelMetadataQuery.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	MetadataHandlerProvider.NoHandler	Exception that indicates there there should be a handler for this class but there is not.

Method Summary

Modifier and Type	Method	Description
<MH extends MetadataHandler<?>> MH	handler(Class<MH> handlerClass)	Provide a handler for the requested metadata class.
default <MH extends MetadataHandler<?>> MH	revise(Class<MH> handlerClass)	Revise the handler for a given kind of metadata.

Method Details

handler

<MH extends MetadataHandler<?>> MH handler(Class<MH> handlerClass)

Provide a handler for the requested metadata class.

Type Parameters:

MH - The metadata type the handler relates to.

Parameters:

handlerClass - The handler interface expected

Returns:

The handler implementation.

revise

default <MH extends MetadataHandler<?>> MH revise(Class<MH> handlerClass)

Revise the handler for a given kind of metadata.

Should be invoked if the existing handler throws a MetadataHandlerProvider.NoHandler exception.

Type Parameters:

MH - The type metadata the handler provides.

Parameters:

handlerClass - The type of class to revise.

Returns:

A new handler that should be used instead of any previous handler provided.