[jira] [Created] (CALCITE-3012) areColumnsUnique for FULL OUTER JOIN could return wrong answer when ignoreNulls is false

["Vineet Garg (JIRA)" <ji...@apache.org>]

Vineet Garg created CALCITE-3012:
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             Summary: 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


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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