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https://issues.apache.org/jira/browse/CALCITE-1037?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15072536#comment-15072536
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Julian Hyde commented on CALCITE-1037:
--------------------------------------
Yes, I suppose you have to treat Correlate the same way as a cartesian join.
(Which is the same as a join where the left and right keys have 0 columns.)
Your work is definitely an improvement over what we have currently. If you add
one or two tests to RelMetadataTest and create a pull request I'd be happy to
accept it.
> Column uniqueness is calculated incorrectly for 'Correlate' expression
> ----------------------------------------------------------------------
>
> Key: CALCITE-1037
> URL: https://issues.apache.org/jira/browse/CALCITE-1037
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.5.0
> Reporter: Alexey Makhmutov
> Assignee: Julian Hyde
>
> Column uniqueness is calculated incorrectly for 'Correlate' expression -- and
> in some cases this leads to java.lang.IndexOutOfBoundsException. Example of
> such code:
> {code}select
> x.v
> from
> (
> select
> t1.v
> from
> (values (1,1),(1,2)) as t1(k,v)
> join (values (1)) as t2(k) on t1.k=t2.k
> ) x,
> lateral
> (
> select
> t.v
> from
> unnest(multiset[x.v]) as t(v)
> ) y
> group by x.v,y.v{code}
> The problems seems to be related to the
> org.apache.calcite.rel.metadata.RelMdColumnUniqueness.areColumnsUnique(Correlate
> rel, ImmutableBitSet columns, boolean ignoreNulls) method -- it just
> delegates uniqueness check to left input without changing columns list, which
> leads to Exception if this list references columns from right input.
> It seems, that right behavior should be following:
> * For Anti/Semi join type keep the current behavior (as resulting rows
> contains fields only from left input).
> * For Left/Inner join type columns set for correlate is unique only if it
> includes unique sets from both sides.
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