[CALCITE-2563] Materialized view rewriting may swap columns in equivalent classes incorrectly

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.17.0
• Fix Version/s: 1.18.0
• Component/s: core
• Assignee: Jesús Camacho Rodríguez
• Reporter: Vladimir Sitnikov
• Created: 16/Sep/18 17:27
• Updated: 27/Feb/24 22:23
• Resolved: 16/Sep/18 18:35

Description

https://github.com/apache/calcite/blob/323200507b72fec152e2f557b3f7f2209a042fe4/core/src/main/java/org/apache/calcite/rel/rules/AbstractMaterializedViewRule.java#L2542

      Set<RexTableInputRef> c1 = nodeToEquivalenceClass.get(p1);
      Set<RexTableInputRef> c2 = nodeToEquivalenceClass.get(p2);
      if (c1 != null && c2 != null) {
        // Both present, we need to merge
        if (c1.size() < c2.size()) {
          // We swap them to merge
          c1 = c2; // <-- HERE.  Should c1 and c2 be actually swapped?
          p1 = p2; // <-- What does this mean? p1 and p2 are not used. Should they be swapped as well just in case
        }
        for (RexTableInputRef newRef : c2) {
          c1.add(newRef);
          nodeToEquivalenceClass.put(newRef, c1);
        }

It looks like c1 vs c2 swap is missing, and a mere c1=c2 is used.
It would likely produce weird results.

/cc jcamachorodriguez