[CALCITE-2695] Simplify casts which are only widening nullability

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.18.0
• Assignee: Zoltan Haindrich
• Reporter: Zoltan Haindrich
• Created: 22/Nov/18 10:16
• Updated: 19/Mar/19 07:30
• Resolved: 28/Nov/18 05:41

Description

There are cases in which casts are added; but they are not neccessary.

  @Test public void testSimplifyRedundantCast() {
    RexNode expr = cast(isTrue(vBoolNotNull()), tBoolean(true));
    assertThat(expr.getType().isNullable(), is(true));
    RexNode result = simplify.simplifyUnknownAs(expr, RexUnknownAs.UNKNOWN);
    assertThat(result.getType().isNullable(), is(false));
  }

Issue Links

• relates to: CALCITE-2932 DruidAdapterIT regression after 1.17 release
• relates to: CALCITE-2933 In Druid adapter, expression like "cast(cast(\"timestamp\" as timestamp) as varchar)" returns as epoch millisecond
• links to: pr934