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https://issues.apache.org/jira/browse/CALCITE-3012?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated CALCITE-3012:
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Labels: pull-request-available (was: )
> areColumnsUnique for FULL OUTER JOIN could return wrong answer when
> ignoreNulls is false
> ----------------------------------------------------------------------------------------
>
> Key: CALCITE-3012
> URL: https://issues.apache.org/jira/browse/CALCITE-3012
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Vineet Garg
> Assignee: Vineet Garg
> Priority: Major
> Labels: pull-request-available
>
> Let's say set of columns passed to this API are join keys and there is one
> NULL key coming from both the inputs. Following code will return true which
> is wrong because the result of FULL. OUTER JOIN with NULL key on both side
> will produce two rows with NULL. Even though this value in respective input
> is unique the result of join may not be unique.
> {code:java}
> Boolean leftUnique = mq.areColumnsUnique(left, leftColumns, ignoreNulls);
> Boolean rightUnique = mq.areColumnsUnique(right, rightColumns,
> ignoreNulls);
> if ((leftColumns.cardinality() > 0)
> && (rightColumns.cardinality() > 0)) {
> if ((leftUnique == null) || (rightUnique == null)) {
> return null;
> } else {
> return leftUnique && rightUnique;
> }
> }
> {code}
> {code:sql}
> create table trepro(i int);
> insert into trepro values(null);
> select * from trepro t1 full outer join trepro t2 on t1.i=t2.i;
> null, null
> null, null
> {code}
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