Class UnionEliminatorRule

All Implemented Interfaces:
SubstitutionRule, TransformationRule

@Enclosing public class UnionEliminatorRule extends RelRule<UnionEliminatorRule.Config> implements SubstitutionRule
UnionEliminatorRule checks to see if its possible to optimize a Union call by eliminating the Union operator altogether in the case the call consists of only one input.
See Also:
  • Constructor Details

  • Method Details

    • 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
    • onMatch

      public void onMatch(RelOptRuleCall call)
      Description copied from class: RelOptRule
      Receives notification about a rule match. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.

      Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RelOptRuleCall.transformTo(org.apache.calcite.rel.RelNode, java.util.Map<org.apache.calcite.rel.RelNode, org.apache.calcite.rel.RelNode>, org.apache.calcite.plan.RelHintsPropagator) to register the expression.

      Specified by:
      onMatch in class RelOptRule
      call - Rule call
      See Also:
    • autoPruneOld

      public boolean autoPruneOld()
      Description copied from interface: SubstitutionRule
      Whether the planner should automatically prune old node when there is at least 1 equivalent rel generated by the rule.

      Default is false, the user needs to prune the old node manually in the rule.

      Specified by:
      autoPruneOld in interface SubstitutionRule