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One problematic part of the current statistics collector design is that there is no reliable way of getting rid of statistics entries. Because of that pgstat_vacuum_stat() (called by [auto-]vacuum) matches all stats for the current database with the catalog contents and tries to drop now-superfluous entries. That's quite expensive. What's worse, it doesn't work on physical replicas, despite physical replicas collection statistics entries. This commit introduces infrastructure to create / drop statistics entries transactionally, together with the underlying catalog objects (functions, relations, subscriptions). pgstat_xact.c maintains a list of stats entries created / dropped transactionally in the current transaction. To ensure the removal of statistics entries is durable dropped statistics entries are included in commit / abort (and prepare) records, which also ensures that stats entries are dropped on standbys. Statistics entries created separately from creating the underlying catalog object (e.g. when stats were previously lost due to an immediate restart) are *not* WAL logged. However that can only happen outside of the transaction creating the catalog object, so it does not lead to "leaked" statistics entries. For this to work, functions creating / dropping functions / relations / subscriptions need to call into pgstat. For subscriptions this was already done when dropping subscriptions, via pgstat_report_subscription_drop() (now renamed to pgstat_drop_subscription()). This commit does not actually drop stats yet, it just provides the infrastructure. It is however a largely independent piece of infrastructure, so committing it separately makes sense. Bumps XLOG_PAGE_MAGIC. Author: Andres Freund <andres@anarazel.de> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de
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/.