[CALCITE-2615] When simplifying NOT-AND-OR, RexSimplify incorrectly applies predicates deduced for operands to the same operands

• Type: Task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.18.0
• Labels: newbie
• Assignee: Zoltan Haindrich
• Reporter: Julian Hyde
• Created: 08/Oct/18 19:21
• Updated: 27/Feb/24 22:24
• Resolved: 17/Oct/18 20:36

Description

When simplifying NOT-AND-OR, RexSimplify incorrectly applies predicates deduced for operands to the same operands.

Here is the test case (add it to RexProgramTest):

  @Test public void testSimplifyNotAnd() {
    final RexNode e = not(
        and(
            gt(and(vBool(1), literal(true)),
                or(literal(true), literal(true), literal(false))),
            gt(isNotNull(vBool(0)), eq(literal(false), vBool(1))),
            or(ne(literal(true), literal(false)),
                ge(vInt(0), literal((Integer) null)))));
    final String expected = "TODO";
   checkSimplify(e, expected);
  }

When you run it, verify will find a combination of assignments such that the simplified expression returns a different result than the original.

The test case is not minimal; sorry. Maybe it reproduces with NOT-OR.

The bug is in RexSimplify.simplifyAndTerms. Put a breakpoint at that line to see the problem. It passes through the operands once, building a list of predicates. Then it passes through the operands again, simplifying each operand. Thus operand1 is simplified using a list of predicates that includes the predicate 'not operand1'. Clearly wrong. kgyrtkirk, I warned that this was possible in our discussions.

Issue Links

• links to: pr880