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Vacuum no longer emits a separate WAL record for each page set all-visible or all-frozen during phase I. Instead, visibility map updates are now included in the XLOG_HEAP2_PRUNE_VACUUM_SCAN record that is already emitted for pruning and freezing. Previously, heap_page_prune_and_freeze() determined whether a page was all-visible, but the corresponding VM bits were only set later in lazy_scan_prune(). Now the VM is updated immediately in heap_page_prune_and_freeze(), at the same time as the heap modifications. This reduces WAL volume produced by vacuum. For now, vacuum is still the only user of heap_page_prune_and_freeze() allowed to set the VM. On-access pruning is not yet able to set the VM. Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Andres Freund <andres@anarazel.de> Reviewed-by: Kirill Reshke <reshkekirill@gmail.com> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Earlier version Reviewed-by: Robert Haas <robertmhaas@gmail.com> Discussion: https://postgr.es/m/flat/CAAKRu_ZMw6Npd_qm2KM%2BFwQ3cMOMx1Dh3VMhp8-V7SOLxdK9-g%40mail.gmail.com
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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.