Class SortJoinTransposeRule

  • public class SortJoinTransposeRule
    extends RelOptRule
    Planner rule that pushes a Sort past a Join.

    At the moment, we only consider left/right outer joins. However, an extension for full outer joins for this rule could be envisioned. Special attention should be paid to null values for correctness issues.

    • Constructor Detail

      • SortJoinTransposeRule

        public SortJoinTransposeRule​(java.lang.Class<? extends Sort> sortClass,
                                     java.lang.Class<? extends Join> joinClass)
        Creates a SortJoinTransposeRule.
      • SortJoinTransposeRule

        public SortJoinTransposeRule​(java.lang.Class<? extends Sort> sortClass,
                                     java.lang.Class<? extends Join> joinClass,
                                     RelBuilderFactory relBuilderFactory)
        Creates a SortJoinTransposeRule.
    • 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
        matches in class RelOptRule
        call - Rule call which has been determined to match all operands of this rule
        whether this RelOptRule matches a given RelOptRuleCall