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https://issues.apache.org/jira/browse/DRILL-1887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14253370#comment-14253370
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Mehant Baid commented on DRILL-1887:
------------------------------------
In ChainedHashTable the condition being checked is (!areNullsEqual &&
isLeftNull && isRightNull), if this condition is satisfied then we return
false. However if nulls aren't equal then if one of the two sides is Null we
should be able to return false so can't this condition be
(!areNullsEqual && (isLeftNull || isRightNull)). In this case we won't go
through the comparator at all?
Otherwise looks good, +1.
> Wrong result for hash join on null valued columns
> -------------------------------------------------
>
> Key: DRILL-1887
> URL: https://issues.apache.org/jira/browse/DRILL-1887
> Project: Apache Drill
> Issue Type: Bug
> Reporter: Rahul Challapalli
> Assignee: Aman Sinha
> Attachments:
> 0001-DRILL-1887-Add-code-gen-for-explicitly-comparing-nul.patch
>
>
> git.commit.id.abbrev=9dfa4a1
> Dataset1:
> {code}
> {
> "col1":1,
> "col2":"abc"
> }
> {
> "col1":2,
> "col2":null
> }
> {code}
> Dataset 2:
> {code}
> {
> "col1":1,
> "col2":null
> }
> {
> "col1":2,
> "col2":null
> }
> {
> "col1":2,
> "col2":"abc"
> }
> {code}
> Query :
> {code}
> select * from `a.json` a join `b.json` b on a.col2=b.col2;
> +------------+------------+------------+------------+
> | col1 | col2 | col10 | col20 |
> +------------+------------+------------+------------+
> | 1 | abc | 2 | abc |
> | 2 | null | 1 | null |
> | 2 | null | 2 | null |
> +------------+------------+------------+------------+
> {code}
> Most database engines treat 2 NULL values as not being equal. This makes it
> hard to compare DRILL's results against any Standard SQL engine. However I am
> not sure whether drill is intentionally designed to behave this way.
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