Package org.apache.calcite.rel.rules

Class JoinCommuteRule

java.lang.Object
org.apache.calcite.plan.RelOptRule
org.apache.calcite.plan.RelRule<JoinCommuteRule.Config>
org.apache.calcite.rel.rules.JoinCommuteRule
All Implemented Interfaces:
TransformationRule
@Enclosing public class JoinCommuteRule extends RelRule<JoinCommuteRule.Config> implements TransformationRule
Planner rule that permutes the inputs to a Join.

Permutation of outer joins can be turned on/off by specifying the swapOuter flag in the constructor.

To preserve the order of columns in the output row, the rule adds a Project.

See Also:

  • Constructor Details

  • Method Details

    • swap

      @Deprecated public static @Nullable RelNode swap(Join join)
      Deprecated.

    • swap

      @Deprecated public static @Nullable RelNode swap(Join join, boolean swapOuterJoins)
      Deprecated.

    • swap

      public static @Nullable RelNode swap(Join join, boolean swapOuterJoins, RelBuilder relBuilder)
      Returns a relational expression with the inputs switched round. Does not modify join. Returns null if the join cannot be swapped (for example, because it is an outer join).
      Parameters:
      join - join to be swapped
      swapOuterJoins - whether outer joins should be swapped
      relBuilder - Builder for relational expressions
      Returns:
      swapped join if swapping possible; else null

    • 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

    • 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
      Parameters:
      call - Rule call
      See Also: