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Posted to dev@calcite.apache.org by James Starr <ja...@gmail.com> on 2020/09/15 22:08:28 UTC

Changes for expanded sub-queries in ON clauses

I created a pull request <https://github.com/apache/calcite/pull/2138> several
days ago to fix sub queries in ON clauses
<https://issues.apache.org/jira/browse/CALCITE-4210>.  Before my changes,
sub-queries rewrites were dropped from an ON clause.

A good way to observe the subquery node being dropped is place to a
breakpoint on
SqlToRelConverter.java:2201
<https://github.com/apache/calcite/blob/1ae20f3e47d9ffab52e934c077d1b7629f798a2f/core/src/main/java/org/apache/calcite/sql2rel/SqlToRelConverter.java#L2201>
and
run a query with sub-query in the ON clause.  The rewrites
are fromBlackboard.root, but are not accounted for when the join is
created. My changes replay the registered subqueries on the right rel node
then
joins on the modified rel right node to left rel node with the rewritten
condition. There is no particular reason I decided on the right over the
left, but they cannot be played on the top of the node to maintain left and
outer join semantics.

I would greatly appreciate comments, suggestions on my changes.

James Starr