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David Rowley d167c19295 Fix possibly uninitialized HeapScanDesc.rs_startblock 
The solution used in 0ca3b1697 to determine the Parallel TID Range
Scan's start location was to modify the signature of
table_block_parallelscan_startblock_init() to allow the startblock
to be passed in as a parameter.  This allows the scan limits to be
adjusted before that function is called so that the limits are picked up
when the parallel scan starts.  The commit made it so the call to
table_block_parallelscan_startblock_init uses the HeapScanDesc's
rs_startblock to pass the startblock to the parallel scan.  That all
works ok for Parallel TID Range scans as the HeapScanDesc rs_startblock
gets set by heap_setscanlimits(), but for Parallel Seq Scans, initscan()
does not initialize rs_startblock, and that results in passing an
uninitialized value to table_block_parallelscan_startblock_init() as
noted by the buildfarm member skink, running Valgrind.

To fix this issue, make it so initscan() sets the rs_startblock for
parallel scans unless we're doing a rescan.  This makes it so
table_block_parallelscan_startblock_init() will be called with the
startblock set to InvalidBlockNumber, and that'll allow the syncscan
code to find the correct start location (when enabled).  For Parallel
TID Range Scans, this InvalidBlockNumber value will be overwritten in
the call to heap_setscanlimits().

initscan() is a bit light on documentation on what's meant to get
initialized where for parallel scans.  From what I can tell, it looks like
it just didn't matter prior to 0ca3b1697 that rs_startblock was left
uninitialized for parallel scans.  To address the light documentation,
I've also added some comments to mention that the syncscan location for
parallel scans is figured out in table_block_parallelscan_startblock_init.
I've also taken the liberty to adjust the if/else if/else code in
initscan() to make it clearer which parts apply to parallel scans and
which parts are for the serial scans.

Author: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAApHDvqALm+k7FyfdQdCw1yF_8HojvR61YRrNhwRQPE=zSmnQA@mail.gmail.com
2025-11-28 12:40:50 +13:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config Remove traces of support for Sun Studio compiler 2025-09-12 07:39:05 +02:00
contrib Have the planner replace COUNT(ANY) with COUNT(*), when possible 2025-11-27 10:43:28 +13:00
doc doc: Add missing tags in pg_buffercache page 2025-11-28 08:00:23 +09:00
src Fix possibly uninitialized HeapScanDesc.rs_startblock 2025-11-28 12:40:50 +13:00
.cirrus.star ci: Simplify ci-os-only handling 2025-08-14 12:09:34 -04:00
.cirrus.tasks.yml ci: Improve OpenBSD core dump backtrace handling. 2025-11-06 21:14:05 +13:00
.cirrus.yml ci: Per-repo configuration for manually trigger tasks 2025-08-14 11:54:03 -04:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Update .editorconfig and .gitattributes for postgresql.conf.sample. 2025-11-18 10:28:36 -06:00
.git-blame-ignore-revs Add commit f63ae72bbc to .git-blame-ignore-revs. 2025-11-18 10:32:22 -06:00
.gitattributes Update .editorconfig and .gitattributes for postgresql.conf.sample. 2025-11-18 10:28:36 -06:00
.gitignore Update top-level .gitignore. 2022-12-04 15:23:00 -05:00
.mailmap Add a Git .mailmap file 2024-11-05 13:56:02 +01:00
aclocal.m4 autoconf: Move export_dynamic determination to configure 2022-12-06 18:55:28 -08:00
configure Fix spurious output in configure 2025-11-06 08:00:57 +01:00
configure.ac Fix spurious output in configure 2025-11-06 08:00:57 +01:00
COPYRIGHT Align organization wording in copyright statement 2025-05-16 11:20:07 -04:00
GNUmakefile.in Allow selecting the git revision to be packaged by "make dist". 2024-05-03 11:08:50 -04:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Remove AIX support 2024-02-28 15:17:23 +04:00
meson.build Add 'make check-tests' behavior to the meson based builds 2025-11-21 17:12:22 -05:00
meson_options.txt Add support for basic NUMA awareness 2025-04-07 23:08:17 +02:00
README.md Revise the style of a paragraph in README.md. 2024-03-21 10:16:41 -05:00

README.md

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/.