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lazy_scan_prune() previously had two separate cases that called visibilitymap_set() after pruning and freezing. These branches were nearly identical except that one attempted to avoid dirtying the heap buffer. However, that situation can never occur — the heap buffer cannot be clean at that point (and we would hit an assertion if it were). In lazy_scan_prune(), when we change a previously all-visible page to all-frozen and the page was recorded as all-visible in the visibility map by find_next_unskippable_block(), the heap buffer will always be dirty. Either we have just frozen a tuple and already dirtied the buffer, or the buffer was modified between find_next_unskippable_block() and heap_page_prune_and_freeze() and then pruned in heap_page_prune_and_freeze(). Additionally, XLogRegisterBuffer() asserts that the buffer is dirty, so attempting to add a clean heap buffer to the WAL chain would assert out anyway. Since the “clean heap buffer with already set VM” case is impossible, the two visibilitymap_set() branches in lazy_scan_prune() can be merged. Doing so makes the intent clearer and emphasizes that the heap buffer must always be marked dirty before being added to the WAL chain. This commit also adds a test case for vacuuming when no heap modifications are required. Currently this ensures that the heap buffer is marked dirty before it is added to the WAL chain, but if we later remove the heap buffer from the VM-set WAL chain or pass it with the REGBUF_NO_CHANGES flag, this test would guard that behavior. Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Andres Freund <andres@anarazel.de> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Reviewed-by: Srinath Reddy Sadipiralla <srinath2133@gmail.com> Reviewed-by: Kirill Reshke <reshkekirill@gmail.com> Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com> Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru> Discussion: https://postgr.es/m/5CEAA162-67B1-44DA-B60D-8B65717E8B05%40gmail.com Discussion: https://postgr.es/m/flat/CAAKRu_ZWx5gCbeCf7PWCv8p5%3D%3Db7EEws0VD2wksDxpXCvCyHvQ%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/.