e6eed40e44
Delay calling BufferGetLSNAtomic() until we finish reading a page that actually contains items that btgettuple will return to the executor. This reduces the number of calls during plain index scans (we'll only call BufferGetLSNAtomic() when _bt_readpage returns true), and totally eliminates calls during index-only scans, bitmap index scans, and plain index scans of an unlogged relation. Currently, when checksums (or wal_log_hints) are enabled, acquiring a page's LSN in BufferGetLSNAtomic() involves locking the buffer header (which involves the use of spinlocks). Testing has shown that enabling page-level checksums causes large regressions with certain workloads, especially on larger multi-socket systems. The regression isn't tied to any Postgres 18 commit. However, Postgres 18 commit 04bec894 made initdb use checksums by default, so it seems prudent to address the problem now. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Tomas Vondra <tomas@vondra.me> Discussion: https://postgr.es/m/941f0190-e3c6-4622-9ac7-c04e936e5fdb@vondra.me Discussion: https://postgr.es/m/CAH2-Wzk-Dg5XWs_jDuiHt4_7ryrSY+n=vxmHY51EVqPDFsKXmg@mail.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/.