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https://issues.apache.org/jira/browse/CALCITE-5927?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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qiang.wang reassigned CALCITE-5927:
-----------------------------------
Assignee: qiang.wang
> LoptOptimizeJoinRule has wrong condition when finding out if Self-Join keys
> are unique
> --------------------------------------------------------------------------------------
>
> Key: CALCITE-5927
> URL: https://issues.apache.org/jira/browse/CALCITE-5927
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.33.0, 1.34.0, 1.35.0
> Reporter: qiang.wang
> Assignee: qiang.wang
> Priority: Minor
>
> There's wrong condition in function _areSelfJoinKeysUnique._
>
> {code:java}
> // Make sure each key on the left maps to the same simple column as the
> // corresponding key on the right
> for (IntPair pair : joinInfo.pairs()) {
> final RelColumnOrigin leftOrigin =
> mq.getColumnOrigin(leftRel, pair.source);
> if (leftOrigin == null || !leftOrigin.isDerived()) {
> return false;
> }
> final RelColumnOrigin rightOrigin =
> mq.getColumnOrigin(rightRel, pair.target);
> if (rightOrigin == null || !rightOrigin.isDerived()) {
> return false;
> }
> if (leftOrigin.getOriginColumnOrdinal()
> != rightOrigin.getOriginColumnOrdinal()) {
> return false;
> }
> } {code}
> The wrong conditions are '{_}if (leftOrigin == null ||
> !leftOrigin.isDerived()){_}' and '{_}if (rightOrigin == null ||
> !rightOrigin.isDerived()){_}'.
> This function wants to find out if the self-join keys are unique. so for each
> self-join key, find
> _leftOrigin_ and _rightOrigin_ first, then will return false if any of them
> is null. But why it returns false when any of them is not _Derived?_ I think
> exactly the opposite is right.
> I think this is a bug comes from CALCITE-4251
> Before that PR, this function will return false only when _leftOrigin_ or
> _rightOrigin_ is null, and the function _RelMetadataQuery#getColumnOrigin_
> will return null if column is derived, so the logic is : 'this function will
> return null when _leftOrigin_ or _rightOrigin_ is null or is derived', but
> now is : 'this function will return null when _leftOrigin_ or _rightOrigin_
> is null or is not derived'.
>
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