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create_lateral_join_info() computes a bunch of information about lateral references between base relations, and then attempts to propagate those markings to appendrel children of the original base relations. But the original coding neglected the possibility of indirect descendants (grandchildren etc). During v11 development we noticed that this was wrong for partitioned-table cases, but failed to realize that it was just as wrong for any appendrel. While the case can't arise for appendrels derived from traditional table inheritance (because we make a flat appendrel for that), nested appendrels can arise from nested UNION ALL subqueries. Failure to mark the lower-level relations as having lateral references leads to confusion in add_paths_to_append_rel about whether unparameterized paths can be built. It's not very clear whether that leads to any user-visible misbehavior; the lack of field reports suggests that it may cause nothing worse than minor cost misestimation. Still, it's a bug, and it leads to failures of Asserts that I intend to add later. To fix, we need to propagate information from all appendrel parents, not just those that are RELOPT_BASERELs. We can still do it in one pass, if we rely on the append_rel_list to be ordered with ancestor relationships before descendant ones; add assertions checking that. While fixing this, we can make a small performance improvement by traversing the append_rel_list just once instead of separately for each appendrel parent relation. Noted while investigating bug #15613, though this patch does not fix that (which is why I'm not committing the related Asserts yet). Discussion: https://postgr.es/m/3951.1549403812@sss.pgh.pa.us |
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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/.