Remus Rusanu created CALCITE-1812:
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Summary: Provide RelMetadataQuery from planner to rules and
invalidate in transformTo
Key: CALCITE-1812
URL: https://issues.apache.org/jira/browse/CALCITE-1812
Project: Calcite
Issue Type: Improvement
Components: core
Reporter: Remus Rusanu
Assignee: Remus Rusanu
Currently rules create a needed {{RelMetadataQuery}} when matched (ie.
{{RuleXxx.onMatch}}. Since rules are called often, on complex query this
triggers a multiplication RMQ instances used. But each new instance carries a
heavy price on performance, because is the RMQ instance that hosts the cache
used to memoize various metadata lookups (like getEstimatedRows,
getPulledUpPredicates, uniqueness and so on). From HIVE-16757 investigation,
the performance impact can be 10x.
The proposal is to have a RelMetadataQuery in the planner and pass it to the
rules as a RelOptRuleCall property. Rules {{onMatch}} can make use of this
instance. The rule call {{transformTo}} can handle invalidating the RMQ
instance.
If code knowingly invalidates metadata properties associated with a node by
means other than transformTo, it should somehow invalidate the current RMQ.
The RMQ invalidation can be made smarter, but my plan right now is to do the
dumb thing and just toss it away. Will revisit this later, depending on
measured impact.
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