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Data loss can happen when the DDLs like ALTER PUBLICATION ... ADD TABLE ... or ALTER TYPE ... that don't take a strong lock on table happens concurrently to DMLs on the tables involved in the DDL. This happens because logical decoding doesn't distribute invalidations to concurrent transactions and those transactions use stale cache data to decode the changes. The problem becomes bigger because we keep using the stale cache even after those in-progress transactions are finished and skip the changes required to be sent to the client. This commit fixes the issue by distributing invalidation messages from catalog-modifying transactions to all concurrent in-progress transactions. This allows the necessary rebuild of the catalog cache when decoding new changes after concurrent DDL. We observed performance regression primarily during frequent execution of *publication DDL* statements that modify the published tables. The regression is minor or nearly nonexistent for DDLs that do not affect the published tables or occur infrequently, making this a worthwhile cost to resolve a longstanding data loss issue. An alternative approach considered was to take a strong lock on each affected table during publication modification. However, this would only address issues related to publication DDLs (but not the ALTER TYPE ...) and require locking every relation in the database for publications created as FOR ALL TABLES, which is impractical. The bug exists in all supported branches, but we are backpatching till 14. The fix for 13 requires somewhat bigger changes than this fix, so the fix for that branch is still under discussion. Reported-by: hubert depesz lubaczewski <depesz@depesz.com> Reported-by: Tomas Vondra <tomas.vondra@enterprisedb.com> Author: Shlok Kyal <shlok.kyal.oss@gmail.com> Author: Hayato Kuroda <kuroda.hayato@fujitsu.com> Reviewed-by: Zhijie Hou <houzj.fnst@fujitsu.com> Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com> Reviewed-by: Amit Kapila <amit.kapila16@gmail.com> Tested-by: Benoit Lobréau <benoit.lobreau@dalibo.com> Backpatch-through: 14 Discussion: https://postgr.es/m/de52b282-1166-1180-45a2-8d8917ca74c6@enterprisedb.com Discussion: https://postgr.es/m/CAD21AoAenVqiMjpN-PvGHL1N9DWnHSq673bfgr6phmBUzx=kLQ@mail.gmail.com |
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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/.