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Mirror of the official PostgreSQL GIT repository. Note that this is just a *mirror* - we don't work with pull requests on github. To contribute, please see https://wiki.postgresql.org/wiki/Submitting_a_Patch
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Peter Geoghegan b5ee4e5202 Avoid nbtree parallel scan currPos confusion. 
Commit 1bd4bc85, which refactored nbtree sibling link traversal, made
_bt_parallel_seize reset the scan's currPos so that things were
consistent with the state of a serial backend moving between pages.
This overlooked the fact that _bt_readnextpage relied on the existing
currPos state to decide when to end the scan -- even though it came from
before the scan was seized.  As a result of all this, parallel nbtree
scans could needlessly behave like full index scans.

To fix, teach _bt_readnextpage to explicitly allow the use of an already
read page's so->currPos when deciding whether to end the scan -- even
during parallel index scans (allow it consistently now).  This requires
moving _bt_readnextpage's seizure of the scan to earlier in its loop.
That way _bt_readnextpage either deals with the true so->currPos state,
or an initialized-by-_bt_parallel_seize currPos state set from when the
scan was seized.  Now _bt_steppage (the most important _bt_readnextpage
caller) takes the same uniform approach to setting up its call using
details taken from so->currPos -- regardless of whether the scan happens
to be parallel or serial.

The new loop structure in _bt_readnextpage is prone to getting confused
by P_NONE blknos set when the rightmost or leftmost page was reached.
We could avoid that by adding an explicit check, but that would be ugly.
Avoid this problem by teaching _bt_parallel_seize to end the parallel
scan instead of returning a P_NONE next block/blkno.  Doing things this
way was arguably a missed opportunity for commit 1bd4bc85.  It allows us
to remove a similar "blkno == P_NONE" check from _bt_first.

Oversight in commit 1bd4bc85, which refactored sibling link traversal
(as part of optimizing nbtree backward scan locking).

Author: Peter Geoghegan <pg@bowt.ie>
Reported-By: Masahiro Ikeda <ikedamsh@oss.nttdata.com>
Diagnosed-By: Masahiro Ikeda <ikedamsh@oss.nttdata.com>
Reviewed-By: Masahiro Ikeda <ikedamsh@oss.nttdata.com>
Discussion: https://postgr.es/m/f8efb9c0f8d1a71b44fd7f8e42e49c25@oss.nttdata.com
2024-11-08 13:10:10 -05:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config Fix __attribute__((target(...))) usage. 2024-11-07 15:27:32 -06:00
contrib Add pg_constraint rows for not-null constraints 2024-11-08 13:28:48 +01:00
doc Add pg_constraint rows for not-null constraints 2024-11-08 13:28:48 +01:00
src Avoid nbtree parallel scan currPos confusion. 2024-11-08 13:10:10 -05:00
.cirrus.star Remove duplicate words in docs and code comments. 2023-10-09 09:18:47 +05:30
.cirrus.tasks.yml Make PG_TEST_EXTRA env var override the "meson setup" option 2024-11-04 14:09:25 +02:00
.cirrus.yml ci: Make compute resources for CI configurable 2023-08-23 15:15:28 -07:00
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aclocal.m4 autoconf: Move export_dynamic determination to configure 2022-12-06 18:55:28 -08:00
configure Fix __attribute__((target(...))) usage. 2024-11-07 15:27:32 -06:00
configure.ac Use __attribute__((target(...))) for AVX-512 support. 2024-11-07 13:58:43 -06:00
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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_options.txt Make PG_TEST_EXTRA env var override the "meson setup" option 2024-11-04 14:09:25 +02:00
meson.build Fix __attribute__((target(...))) usage. 2024-11-07 15:27:32 -06:00
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/.