Class ChainedRelMetadataProvider

All Implemented Interfaces:
Direct Known Subclasses:

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.

  • Constructor Details

    • ChainedRelMetadataProvider

      protected ChainedRelMetadataProvider(<RelMetadataProvider> providers)
      Creates a chain.
  • Method Details

    • equals

      public boolean equals(@Nullable Object obj)
      equals in class Object
    • hashCode

      public int hashCode()
      hashCode in class Object
    • apply

      @Deprecated public <@Nullable M extends @Nullable Metadata> @Nullable UnboundMetadata<M> apply(Class<? extends RelNode> relClass, Class<? extends @Nullable 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
      relClass - Type of relational expression
      metadataClass - Type of metadata
      Function that will field a metadata instance; or null if this provider cannot supply metadata of this type
    • handlers

      @Deprecated public <M extends Metadata><Method,MetadataHandler<M>> handlers(MetadataDef<M> def)
      Specified by:
      handlers in interface RelMetadataProvider
    • handlers

      public List<MetadataHandler<?>> handlers(Class<? extends MetadataHandler<?>> handlerClass)
      Description copied from interface: RelMetadataProvider
      Retrieves a list of MetadataHandler for implements a particular MetadataHandler.class. The resolution order is specificity of the relNode class, with preference given to handlers that occur earlier in the list.

      For instance, given a return list of {A, B, C} where A implements RelNode and Scan, B implements Scan, and C implements LogicalScan and Filter.

      Scan dispatches to a.method(Scan); LogicalFilter dispatches to c.method(Filter); LogicalScan dispatches to c.method(LogicalScan); Aggregate dispatches to a.method(RelNode).

      The behavior is undefined if the class hierarchy for dispatching is not a tree.

      Specified by:
      handlers in interface RelMetadataProvider
    • of

      public static RelMetadataProvider of(List<RelMetadataProvider> list)
      Creates a chain.