[GitHub] [calcite] rubenada commented on a change in pull request #2079: [CALCITE-4126] Stackoverflow error when applying JoinCommuteRule (Liya Fan)

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

rubenada commented on a change in pull request #2079:
URL: https://github.com/apache/calcite/pull/2079#discussion_r460676250



##########
File path: core/src/main/java/org/apache/calcite/rel/rules/JoinCommuteRule.java
##########
@@ -160,28 +176,7 @@ public void onMatch(final RelOptRuleCall call) {
     if (swapped == null) {
       return;
     }
-
-    // The result is either a Project or, if the project is trivial, a
-    // raw Join.
-    final Join newJoin =
-        swapped instanceof Join
-            ? (Join) swapped
-            : (Join) swapped.getInput(0);
-
     call.transformTo(swapped);
-
-    // We have converted join='a join b' into swapped='select
-    // a0,a1,a2,b0,b1 from b join a'. Now register that project='select
-    // b0,b1,a0,a1,a2 from (select a0,a1,a2,b0,b1 from b join a)' is the
-    // same as 'b join a'. If we didn't do this, the swap join rule
-    // would fire on the new join, ad infinitum.
-    final RelBuilder relBuilder = call.builder();
-    final List<RexNode> exps =
-        RelOptUtil.createSwappedJoinExprs(newJoin, join, false);
-    relBuilder.push(swapped)
-        .project(exps, newJoin.getRowType().getFieldNames());
-
-    call.getPlanner().ensureRegistered(relBuilder.build(), newJoin);

Review comment:
       If I am not mistaken, this code that is now being removed, is supposed to prevent the rule from firing endlessly. Do we know why it is not working?




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