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When pull_up_sublinks() converts a sublink to an antijoin, it builds a JoinExpr with no RTE, on the grounds that nothing above the join can reference its RHS. That overlooks PlaceHolderVars. A PHV with no Vars of its own is evaluated at its phrels, and for the outputs of a pulled-up subquery phrels is all the relids in the subquery's jointree, including the RHS of such a join. A qual using the PHV thus appears to reference the RHS rels, and can be pushed down into the RHS as a parameterized join clause. There it has the opposite of the intended effect: outer rows that fail the qual find no match and are emitted, giving wrong results. For an outer join, including an antijoin made by reducing a left join, this cannot happen because the join's relid is among the qual's relids. Before v16, the qual's nullable_relids prevented it. To fix, make a join RTE for an antijoin built from a sublink, so that it has a relid like any other outer join. Semijoins are left as they are: a qual evaluated within a semijoin's RHS does not change the result. Back-patch to v16. Before that, the qual's nullable_relids included the antijoin's RHS, which kept the qual from being moved there; that protection went away when nullable_relids was replaced by outer-join relids. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: wenhui qiu <qiuwenhuifx@gmail.com> Discussion: https://postgr.es/m/CAMbWs4_rEdcG89BgC-AO7b+Bf2z8w3976+4zP==Urt=CXB1hsg@mail.gmail.com Backpatch-through: 16
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. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.