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After applying outer-join identity 3 in the forward direction, it was possible for the planner to mistakenly apply a qual clause from above the two outer joins at the now-lower join level. This can give the wrong answer, since a value that would get nulled by the now-upper join might not yet be null. To fix, when we perform such a transformation, consider that the now-lower join hasn't really completed the outer join it's nominally responsible for and thus its relid set should not include that OJ's relid (nor should its output Vars have that nullingrel bit set). Instead we add those bits when the now-upper join is performed. The existing rules for qual placement then suffice to prevent higher qual clauses from dropping below the now-upper join. There are a few complications from needing to consider transitive closures in case multiple pushdowns have happened, but all in all it's not a very complex patch. This is all new logic (from 2489d76c4) so no need to back-patch. The added test cases all have the same results as in v15. Tom Lane and Richard Guo Discussion: https://postgr.es/m/0b819232-4b50-f245-1c7d-c8c61bf41827@postgrespro.ru
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/.