db6736c93c
Commit 9dc718bd added a "logically unchanged by UPDATE" hinting mechanism, which is currently used within nbtree indexes only (see commit d168b666). This mechanism determined whether or not the incoming item is a logically unchanged duplicate (a duplicate needed only for MVCC versioning purposes) once per row updated per non-HOT update. This approach led to memory leaks which were noticeable with an UPDATE statement that updated sufficiently many rows, at least on tables that happen to have an expression index. On HEAD, fix the issue by adding a cache to the executor's per-index IndexInfo struct. Take a different approach on Postgres 14 to avoid an ABI break: simply pass down the hint to all indexes unconditionally with non-HOT UPDATEs. This is deemed acceptable because the hint is currently interpreted within btinsert() as "perform a bottom-up index deletion pass if and when the only alternative is splitting the leaf page -- prefer to delete any LP_DEAD-set items first". nbtree must always treat the hint as a noisy signal about what might work, as a strategy of last resort, with costs imposed on non-HOT updaters. (The same thing might not be true within another index AM that applies the hint, which is why the original behavior is preserved on HEAD.) Author: Peter Geoghegan <pg@bowt.ie> Reported-By: Klaudie Willis <Klaudie.Willis@protonmail.com> Diagnosed-By: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/261065.1639497535@sss.pgh.pa.us Backpatch: 14-, where the hinting mechanism was added.
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/.