[GitHub] [calcite] libenchao commented on a diff in pull request #2761: [CALCITE-5073] JoinConditionPushRule cannot infer 'LHS.C1 = LHS.C2' f…

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

libenchao commented on code in PR #2761:
URL: https://github.com/apache/calcite/pull/2761#discussion_r876973627


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core/src/main/java/org/apache/calcite/rel/rules/FilterJoinRule.java:
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@@ -225,6 +232,105 @@ protected void perform(RelOptRuleCall call, @Nullable Filter filter,
     call.transformTo(relBuilder.build());
   }
 
+  /**
+   * Infer more equal conditions for the Join Condition.
+   *
+   * <p> For example, in {@code SELECT * FROM T1, T2, T3 WHERE T1.id = T3.id AND T2.id = T3.id},
+   * we can infer {@code T1.id = T2.id} for the first Join node from second Join node's condition:
+   * {@code T1.id = T3.id AND T2.id = T3.id}.
+   *
+   * <p>For the above SQL, the second Join's condition is {@code T1.id = T3.id AND T2.id = T3.id}.
+   * After inference, the final condition would be: {@code T1.id = T2.id AND T1.id = T3.id}, the
+   * {@code T1.id = T2.id} can be further pushed into LHS.
+   *
+   * @param rexNodes the Join condition
+   * @param join the Join node
+   */
+  protected void inferJoinEqualConditions(List<RexNode> rexNodes, Join join) {
+    final List<Set<Integer>> equalSets = new ArrayList<>();
+    final List<RexNode> result = new ArrayList<>(rexNodes.size());
+    for (RexNode rexNode : rexNodes) {
+      if (rexNode.isA(SqlKind.EQUALS)) {
+        final RexNode op1 = ((RexCall) rexNode).getOperands().get(0);
+        final RexNode op2 = ((RexCall) rexNode).getOperands().get(1);

Review Comment:
   I agree with you. However, I just followed  `FilterJoinRule#validateJoinFilters`, and kept it same. (Of course, if you still think we'd better to make it a no side-effect method, I can refactor it)



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