Package org.apache.calcite.rel.metadata

Class RelMdPredicates.JoinConditionBasedPredicateInference.ExprsItr

  • All Implemented Interfaces:
    java.util.Iterator<Mapping>
    Enclosing class:
    RelMdPredicates.JoinConditionBasedPredicateInference
    class RelMdPredicates.JoinConditionBasedPredicateInference.ExprsItr
extends java.lang.Object
implements java.util.Iterator<Mapping>
    Given an expression returns all the possible substitutions.

    For example, for an expression 'a + b + c' and the following equivalences: 

     a : {a, b}
 b : {a, b}
 c : {c, e}

    The following Mappings will be returned: 

     {a → a, b → a, c → c}
 {a → a, b → a, c → e}
 {a → a, b → b, c → c}
 {a → a, b → b, c → e}
 {a → b, b → a, c → c}
 {a → b, b → a, c → e}
 {a → b, b → b, c → c}
 {a → b, b → b, c → e}

    which imply the following inferences: 

     a + a + c
 a + a + e
 a + b + c
 a + b + e
 b + a + c
 b + a + e
 b + b + c
 b + b + e

    • Field Detail

      • columns

        final int[] columns

      • columnSets

        final java.util.BitSet[] columnSets

      • iterationIdx

        final int[] iterationIdx

      • firstCall

        boolean firstCall

    • Method Detail

      • hasNext

        public boolean hasNext()
        Specified by:
        hasNext in interface java.util.Iterator<Mapping>

      • next

        public Mapping next()
        Specified by:
        next in interface java.util.Iterator<Mapping>

      • remove

        public void remove()
        Specified by:
        remove in interface java.util.Iterator<Mapping>

      • computeNextMapping

        private void computeNextMapping​(int level)

      • initializeMapping

        private void initializeMapping()