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The check for window functions (point 4) guarded on the wrong bit: it tested UNSAFE_NOTIN_DISTINCTON_CLAUSE while setting UNSAFE_NOTIN_PARTITIONBY_CLAUSE. Each check in this loop guards on the same bit it is about to set, as an idempotency optimization, since unsafeFlags[] is accumulated across the arms of a set operation and there is no point recomputing a column's status once its bit is present. This is not a live bug. When UNSAFE_NOTIN_PARTITIONBY_CLAUSE is already set but UNSAFE_NOTIN_DISTINCTON_CLAUSE is not, the guard fails to skip targetIsInAllPartitionLists() and recomputes it, but setting the same bit again changes nothing. When UNSAFE_NOTIN_DISTINCTON_CLAUSE is already set, point 4 is skipped and UNSAFE_NOTIN_PARTITIONBY_CLAUSE is left unset; but such a column is already unsafe for pushdown via UNSAFE_NOTIN_DISTINCTON_CLAUSE, so the outcome is unchanged. To fix, test UNSAFE_NOTIN_PARTITIONBY_CLAUSE, matching the bit being set and the pattern of the surrounding checks. Back-patch to v15, where the buggy check was introduced. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Tender Wang <tndrwang@gmail.com> Reviewed-by: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/CAMbWs49Q_xnF_P2QSUyDzJ34MnrO7dh-cUAaK2HJPgSgh88NcA@mail.gmail.com Backpatch-through: 15
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/.