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A clause connecting the same two EC members can be requested from the EC machinery in different contexts. When building parameterized index paths for a relation, generate_implied_equalities_for_column derives an indexable clause with parent_ec set, to mark it as redundant with other join clauses derived from the same EC. Meanwhile, at a join where the relations of a multi-relation EC member first come together, generate_join_implied_equalities emits a clause equating the same two members with parent_ec unset, since that clause is the sole enforcer of its member there and must not be dropped as redundant. Because create_join_clause treats parent_ec as part of its cache-lookup key, such requests can yield two different RestrictInfos for the same condition, carrying different rinfo_serials. This breaks the assumption that one condition has exactly one serial number, which create_nestloop_path relies on to drop join clauses that are already enforced within a parameterized inner path. As a result, the same condition could be enforced twice at different plan levels, wasting execution effort and applying the clause's selectivity twice, underestimating the join's row count. To fix, make create_join_clause copy the rinfo_serial from an existing clause that connects the same two members with the opposite parent_ec marking, so that the two clauses keep their distinct markings but are recognized as the same condition. As a result, a duplicate join filter disappears from one of the existing regression plans (the "cardinal_number" query in join.sql); the other plan changes are join-order differences between plans of essentially equal cost. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/CAMbWs4-3yZeBMGQDpmYRPdV-sL_=6H2AN=MoeneOT+VUk28PPg@mail.gmail.com Backpatch-through: 19
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/19/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/19/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.