Class CassandraRules.CassandraProjectRule

    • Constructor Detail

      • CassandraProjectRule

        private CassandraProjectRule()
    • 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
      • convert

        public RelNode convert​(RelNode rel)
        Description copied from class: ConverterRule
        Converts a relational expression to the target trait(s) of this rule.

        Returns null if conversion is not possible.

        Specified by:
        convert in class ConverterRule