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When prepare_sort_from_pathkeys() cannot find a pathkey's expression in the input plan's targetlist, it adds a resjunk entry computing an EquivalenceClass member's expression. It copied that expression as-is, without replacing lateral references with nestloop Params the way build_path_tlist() does for the rest of the targetlist. This matters when the sort key contains a PlaceHolderVar whose expression has a lateral reference, and the sort is placed directly atop the plan node that evaluates the PlaceHolderVar. The targetlist already contains the PlaceHolderVar, so the sort key is considered computable, but the entry added for it still has the outer relation's Var inside the PlaceHolderVar. If the node is a join, setrefs.c fails with "variable not found in subplan target lists". If it is a scan, setrefs.c leaves the Var in place, and the executor fetches it from the scan tuple, leading to wrong results. To fix, pass root to prepare_sort_from_pathkeys() and apply replace_nestloop_params() to the expression before adding it to the targetlist. Back-patch to all supported branches. Author: Richard Guo <guofenglinux@gmail.com> Discussion: https://postgr.es/m/CAMbWs49LWNm7_OxuW1V71wLi+Ev3KbfY1bMY36uydNKwSPnbtQ@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/.