[GitHub] [calcite] rubenada commented on a diff in pull request #2848: [CALCITE-5201] Improve SemiJoinRule to match Join's right input which is unique for Join keys

[GitBox <gi...@apache.org>]

rubenada commented on code in PR #2848:
URL: https://github.com/apache/calcite/pull/2848#discussion_r942672540


##########
core/src/main/java/org/apache/calcite/rel/rules/SemiJoinRule.java:
##########
@@ -232,6 +234,87 @@ default JoinToSemiJoinRuleConfig withOperandFor(Class<Join> joinClass,
     }
   }
 
+  /**
+   * SemiJoinRule that matches a Project on top of a Join with a RelNode
+   * which is unique for Join's right keys.
+   *
+   * @see CoreRules#JOIN_ON_UNIQUE_TO_SEMI_JOIN */
+  public static class JoinOnUniqueToSemiJoinRule extends SemiJoinRule {
+
+    /** Creates a JoinOnUniqueToSemiJoinRule. */
+    protected JoinOnUniqueToSemiJoinRule(JoinOnUniqueToSemiJoinRuleConfig config) {
+      super(config);
+    }
+
+    @Override public boolean matches(RelOptRuleCall call) {
+      final Project project = call.rel(0);
+      final Join join = call.rel(1);
+      final RelNode left = call.rel(2);
+
+      final ImmutableBitSet bits =
+          RelOptUtil.InputFinder.bits(project.getProjects(), null);
+      final ImmutableBitSet rightBits =
+          ImmutableBitSet.range(left.getRowType().getFieldCount(),
+              join.getRowType().getFieldCount());
+      return !bits.intersects(rightBits);
+    }
+
+    @Override public void onMatch(RelOptRuleCall call) {
+      final Project project = call.rel(0);
+      final Join join = call.rel(1);
+      final RelNode left = call.rel(2);
+      final RelNode right = call.rel(3);
+
+      // Same with ProjectToSemiJoinRule
+      if (right instanceof Aggregate) {

Review Comment:
   Should we rather add in the new rule's config a predicate to not match Aggregates on the join RHS:
   ```
   ...
   b2 -> b2.operand(Join.class).predicate(SemiJoinRule::isJoinTypeSupported).inputs(
     b3 -> b3.operand(RelNode.class).anyInputs(),
     b4 -> b4.operand(RelNode.class).predicate(n -> !(n instanceof Aggregate)).anyInputs()
   )))
   ```
   Rather than matching it with two rules (the old and the new) and creating two times the same result?



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