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When building sort keys for a child relation, such as the per-child sort columns of a MergeAppend over partitionwise child joins, prepare_sort_from_pathkeys() may need to compute an EquivalenceClass member from the child's targetlist. find_computable_ec_member() accepts a member if all the Vars and quasi-Vars it contains appear in that targetlist. It ignores child members that don't belong to the given relids, but it can still choose a parent member. Usually that is harmless, since a parent member's Vars never appear in a child's targetlist. PlaceHolderVars are different: equal() ignores their phexpr and phrels, so a parent PlaceHolderVar matches its translated copy in the child's targetlist. As a result, an untranslated parent expression could be added to the child plan's targetlist, leading to "variable not found in subplan target lists" errors from setrefs.c. To fix, when relids is given, also ignore parent members that don't belong to it. This changes nothing for a non-child relation, because any member computable from its targetlist belongs to it anyway. When relids is NULL, only child members are filtered, as before. Also update the comments for prepare_sort_from_pathkeys() to reflect that 'relids' can identify a non-child relation being sorted, which has long been the case. Back-patch to all supported branches. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: wenhui qiu <qiuwenhuifx@gmail.com> Discussion: https://postgr.es/m/CAMbWs48bLLEGy6YC+n01w6=YR=28cj_kpoKcAgOHQR7jbtLb6w@mail.gmail.com Backpatch-through: 14
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/.