fix slow single-value array-contains filter on multi-valued properties#535
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cportele wants to merge 1 commit into
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fix slow single-value array-contains filter on multi-valued properties#535cportele wants to merge 1 commit into
cportele wants to merge 1 commit into
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A_CONTAINS on a multi-valued property is encoded as ... IN (<values>) GROUP BY <id> HAVING count(distinct <col>) = <n> For a single value n is 1 and the HAVING is tautological: every group selected by IN (<one value>) trivially has one distinct value, so the predicate is always true. PostgreSQL has no selectivity estimate for a post-aggregate count(distinct) filter and falls back to a tiny default row count. That misestimate can drive a nested-loop plan that re-evaluates other predicates per row (for example a large id membership set), making the query extremely slow. Drop the redundant HAVING for the single-value case (equivalent to the A_OVERLAPS encoding) so the planner sees an accurate grouped-row count. Multi-value filters keep the HAVING, which remains semantically required.
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A_CONTAINSon a multi-valued property is encoded as... IN (<values>) GROUP BY <id> HAVING count(distinct <col>) = <n>For a single value
nis 1 and theHAVINGis tautological: every group selected byIN (<one value>)trivially has one distinct value, so the predicate is always true.PostgreSQL has no selectivity estimate for a post-aggregate
count(distinct)filter and falls back to a tiny default row count. That misestimate can drive a nested-loop plan that re-evaluates other predicates per row (for example a large id membership set), making the query extremely slow.Drop the redundant
HAVINGfor the single-value case (equivalent to theA_OVERLAPSencoding) so the planner sees an accurate grouped-row count. Multi-value filters keep theHAVING, which remains semantically required.