[IGNITE-16493] Calcite engine. Decorrelation after subquery rewrite

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: sql
• Labels: calcite calcite2-required calcite3-required
• Assignee: Unassigned
• Reporter: Aleksey Plekhanov
• Created: 08/Feb/22 06:51
• Updated: 29/Apr/24 11:30

Description

Currently decorrelation is performed in SqlToRelConverter, but after this PlannerPhase.HEP_DECORRELATE planning phase is executed (which actually rewrites subqueries into correlates, but doesn't perform decorrelation). In some cases, other types of join can cost less than correlated nested loop join, so we can try to decorrelate the query plan again after PlannerPhase.HEP_DECORRELATE phase (call RelDecorrelator.decorrelateQuery).
PlannerPhase.HEP_DECORRELATE should be also renamed to something like "HEP_REWRITE_SUBQUERY".

Issue Links

• is part of: IGNITE-12248 Apache Calcite based query execution engine
• relates to: IGNITE-22092 Sql. Implement subquery decorrelation
• relates to: IGNITE-21579 Sql. Investigate performance bottlenecks in sql engine
• links to: GitHub Pull Request #9832