Class AggregateCaseToFilterRule


  • public class AggregateCaseToFilterRule
    extends RelOptRule
    Rule that converts CASE-style filtered aggregates into true filtered aggregates.

    For example,

    SELECT SUM(CASE WHEN gender = 'F' THEN salary END)
    FROM Emp

    becomes

    SELECT SUM(salary) FILTER (WHERE gender = 'F')
    FROM Emp
    • Constructor Detail

      • AggregateCaseToFilterRule

        protected AggregateCaseToFilterRule​(RelBuilderFactory relBuilderFactory,
                                            java.lang.String description)
        Creates an AggregateCaseToFilterRule.
    • Method Detail

      • matches

        public boolean matches​(RelOptRuleCall call)
        Description copied from class: RelOptRule
        Returns whether this rule could possibly match the given operands.

        This method is an opportunity to apply side-conditions to a rule. The RelOptPlanner calls this method after matching all operands of the rule, and before calling RelOptRule.onMatch(RelOptRuleCall).

        In implementations of RelOptPlanner which may queue up a matched RelOptRuleCall for a long time before calling RelOptRule.onMatch(RelOptRuleCall), this method is beneficial because it allows the planner to discard rules earlier in the process.

        The default implementation of this method returns true. It is acceptable for any implementation of this method to give a false positives, that is, to say that the rule matches the operands but have RelOptRule.onMatch(RelOptRuleCall) subsequently not generate any successors.

        The following script is useful to identify rules which commonly produce no successors. You should override this method for these rules:

        awk '
         /Apply rule/ {rule=$4; ruleCount[rule]++;}
         /generated 0 successors/ {ruleMiss[rule]++;}
         END {
           printf "%-30s %s %s\n", "Rule", "Fire", "Miss";
           for (i in ruleCount) {
             printf "%-30s %5d %5d\n", i, ruleCount[i], ruleMiss[i];
           }
         } ' FarragoTrace.log
        Overrides:
        matches in class RelOptRule
        Parameters:
        call - Rule call which has been determined to match all operands of this rule
        Returns:
        whether this RelOptRule matches a given RelOptRuleCall
      • soleArgument

        private static int soleArgument​(AggregateCall aggregateCall)
        Returns the argument, if an aggregate call has a single argument, otherwise -1.
      • isThreeArgCase

        private static boolean isThreeArgCase​(RexNode rexNode)
      • isIntLiteral

        private static boolean isIntLiteral​(RexNode rexNode)