jcamachor commented on a change in pull request #1185: [CALCITE-3012]
areColumnsUnique for FULL OUTER JOIN could return wrong answer when ignoreNulls
is false
URL: https://github.com/apache/calcite/pull/1185#discussion_r280569656
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File path:
core/src/main/java/org/apache/calcite/rel/metadata/RelMdColumnUniqueness.java
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@@ -254,6 +255,13 @@ public Boolean areColumnsUnique(Join rel,
RelMetadataQuery mq,
final ImmutableBitSet leftColumns = leftAndRightColumns.left;
final ImmutableBitSet rightColumns = leftAndRightColumns.right;
+ // for FULL OUTER JOIN if columns contain column from both inputs it is not
+ // guranteed that the result will be unique
+ if (!ignoreNulls && rel.getJoinType() == JoinRelType.FULL
+ && leftColumns.cardinality() > 0 && rightColumns.cardinality() > 0) {
+ return false;
+ }
Review comment:
I see, makes sense. However, it seems comments are not consistent wrt
behavior. Probably there is not a rule that makes a distinction between 'false'
and 'null' right now, so it is fine. Maybe you can create a follow-up (you can
leave it unassigned) so we can discuss and fix it. I will merge this patch
shortly.
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