Maksim Zhuravkov created IGNITE-22092:
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Summary: Sql. Implement subquery decorrelation.
Key: IGNITE-22092
URL: https://issues.apache.org/jira/browse/IGNITE-22092
Project: Ignite
Issue Type: Improvement
Components: sql
Reporter: Maksim Zhuravkov
Rewriting correlated subqueries provides significant performance boost by
removing redundant loops during execution and by allowing subsequent
optimisations of flattened plans during planning.
P.S.
Apache calcite provides some means to decorrelate subqueries
(viaRelDecorrelator) but unfortunetly they are:
- produce incorrect results (see
https://issues.apache.org/jira/browse/IGNITE-16493 where decorrelating
subquery produces incorrect result because a resulting plan contains a join
with `equality` instead of is `not distinct from` predicate (thus breaking
queries for tables that contain NULLs).
- limited in scope.
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