Class ChainedRelMetadataProvider

    • Constructor Detail

      • ChainedRelMetadataProvider

        protected ChainedRelMetadataProvider​(com.google.common.collect.ImmutableList<RelMetadataProvider> providers)
        Creates a chain.
    • Method Detail

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class Object
      • apply

        public <M extends MetadataUnboundMetadata<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