[jira] [Commented] (CALCITE-3021) ArrayEqualityComparer should use Arrays#deepEquals/deepHashCode instead of Arrays#equals/hashCode

["Stamatis Zampetakis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-3021?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16844661#comment-16844661 ] 

Stamatis Zampetakis commented on CALCITE-3021:
----------------------------------------------

I think we should rephrase the JIRA (summary/description) focusing on the real problem which according to the test that [~rubenql] added 

{code:sql}
select distinct * from (values
    (1, ROW(1,1)),
    (1, ROW(1,1)),
    (2, ROW(2,2))) as v(id,struct);
+----+--------+
| ID | STRUCT |
+----+--------+
|  1 | {1, 1} |
|  2 | {2, 2} |
+----+--------+
(2 rows)
{code}

is comparisons of structured types. I don't remember what the SQL standard says with respect to this; I guess we should verify. 

> ArrayEqualityComparer should use Arrays#deepEquals/deepHashCode instead of Arrays#equals/hashCode
> -------------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-3021
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3021
>             Project: Calcite
>          Issue Type: Bug
>    Affects Versions: 1.19.0
>            Reporter: Ruben Quesada Lopez
>            Assignee: Ruben Quesada Lopez
>            Priority: Minor
>              Labels: pull-request-available
>             Fix For: 1.20.0
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> Currently, ArrayEqualityComparer (which is used as comparer for JavaRowFormat.ARRAY) performs the array comparison based on Arrays#equals and Arrays#hashCode (see Functions.java):
> {code: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);
>     }
>   }
> {code}
> 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:
> {code:java}
>   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);
>     }
>   }
> {code}



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