[CALCITE-3021] Equality of nested ROWs returns false for identical values

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.19.0
• Fix Version/s: 1.20.0
• Labels: pull-request-available
• Assignee: Ruben Q L
• Reporter: Ruben Q L
• Created: 24/Apr/19 12:36
• Updated: 07/Nov/19 14:49
• Resolved: 27/May/19 17:15

Description

Problem can be reproduced via:

select distinct * from (values
    (1, ROW(1,1)),
    (1, ROW(1,1)),
    (2, ROW(2,2))) as v(id,struct);

Which incorrectly returns a duplicated value:

+----+--------+
| ID | STRUCT |
+----+--------+
|  1 | {1, 1} |
|  1 | {1, 1} |
|  2 | {2, 2} |
+----+--------+
(3 rows)

The root cause is that currently ArrayEqualityComparer (which is used as comparer for JavaRowFormat.ARRAY) performs the array comparison based on Arrays#equals and Arrays#hashCode (see Functions.java):

  private static class ArrayEqualityComparer implements EqualityComparer<Object[]> {
    public boolean equal(Object[] v1, Object[] v2) {
      return Arrays.equals(v1, v2);
    }
    public int hashCode(Object[] t) {
      return Arrays.hashCode(t);
    }
  }

This will lead to incorrect comparisons in case of multidimensional arrays, e.g. a row (array) with a struct field (another array) inside. To fix the issue, Arrays#deepEquals / Arrays#deepHashCode should be used:

  private static class ArrayEqualityComparer implements EqualityComparer<Object[]> {
    public boolean equal(Object[] v1, Object[] v2) {
      return Arrays.deepEquals(v1, v2);
    }
    public int hashCode(Object[] t) {
      return Arrays.deepHashCode(t);
    }
  }

Issue Links

• relates to: CALCITE-3482 Equality of nested ROWs returns false for identical literal value
• links to: GitHub Pull Request #1183