qiang.wang created CALCITE-5927:
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Summary: 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: 1.35.0, 1.34.0, 1.33.0
Reporter: qiang.wang
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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