upstream/postgresql
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2026-02-20 08:20:55 -05:00
Code Issues Projects Releases Packages Wiki Activity Actions
Base de données relationnelle
61756 commits 38 branches 674 tags 843 MiB
C 84.8%
PLpgSQL 6.1%
Perl 4.7%
Yacc 1.2%
Meson 0.7%
Other 2.4%
Find a file
Nathan Bossart 161a3e8b68 pg_upgrade: Use COPY for large object metadata. 
Presently, pg_dump generates commands like

    SELECT pg_catalog.lo_create('5432');
    ALTER LARGE OBJECT 5432 OWNER TO alice;
    GRANT SELECT ON LARGE OBJECT 5432 TO bob;

for each large object.  This is particularly slow at restore time,
especially when there are tens or hundreds of millions of large
objects.  From reports and personal experience, such slow restores
seem to be most painful when encountered during pg_upgrade.  This
commit teaches pg_dump to instead dump pg_largeobject_metadata and
the corresponding pg_shdepend rows when in binary upgrade mode,
i.e., pg_dump now generates commands like

    COPY pg_catalog.pg_largeobject_metadata (oid, lomowner, lomacl) FROM stdin;
    5432	16384	{alice=rw/alice,bob=r/alice}
    \.

    COPY pg_catalog.pg_shdepend (dbid, classid, objid, objsubid, refclassid, refobjid, deptype) FROM stdin;
    5	2613	5432	0	1260	16384	o
    5	2613	5432	0	1260	16385	a
    \.

Testing indicates the COPY approach can be significantly faster.
To do any better, we'd probably need to find a way to copy/link
pg_largeobject_metadata's files during pg_upgrade, which would be
limited to upgrades from >= v16 (since commit 7b378237aa changed
the storage format for aclitem, which is used for
pg_largeobject_metadata.lomacl).

Note that this change only applies to binary upgrade mode (i.e.,
dumps initiated by pg_upgrade) since it inserts rows directly into
catalogs.  Also, this optimization can only be used for upgrades
from >= v12 because pg_largeobject_metadata was created WITH OIDS
in older versions, which prevents pg_dump from handling
pg_largeobject_metadata.oid properly.  With some extra effort, it
might be possible to support upgrades from older versions, but the
added complexity didn't seem worth it to support versions that will
have been out-of-support for nearly 3 years by the time this change
is released.

Experienced hackers may remember that prior to v12, pg_upgrade
copied/linked pg_largeobject_metadata's files (see commit
12a53c732c).  Besides the aforementioned storage format issues,
this approach failed to transfer the relevant pg_shdepend rows, and
pg_dump still had to generate an lo_create() command per large
object so that creating the dependent comments and security labels
worked.  We could perhaps adopt a hybrid approach for upgrades from
v16 and newer (i.e., generate lo_create() commands for each large
object, copy/link pg_largeobject_metadata's files, and COPY the
relevant pg_shdepend rows), but further testing is needed.

Reported-by: Hannu Krosing <hannuk@google.com>
Suggested-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Hannu Krosing <hannuk@google.com>
Reviewed-by: Nitin Motiani <nitinmotiani@google.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAMT0RQSS-6qLH%2BzYsOeUbAYhop3wmQTkNmQpo5--QRDUR%2BqYmQ%40mail.gmail.com
2025-07-18 10:59:46 -05:00
.github Add CODE_OF_CONDUCT.md, CONTRIBUTING.md, and SECURITY.md. 2024-07-02 13:03:58 -05:00
config oauth: Run Autoconf tests with correct compiler flags 2025-07-11 10:06:41 -07:00
contrib Fix a typo in the deparseArrayCoerceExpr() header comment 2025-07-18 18:40:07 +03:00
doc doc: Add note about how to use pg_overexplain. 2025-07-17 10:25:59 -05:00
src pg_upgrade: Use COPY for large object metadata. 2025-07-18 10:59:46 -05:00
.cirrus.star Remove duplicate words in docs and code comments. 2023-10-09 09:18:47 +05:30
.cirrus.tasks.yml Hide ICU C++ APIs from pg_locale.h 2025-07-09 14:20:22 +07:00
.cirrus.yml ci: Test NetBSD and OpenBSD 2025-02-12 09:40:07 -05:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add script to keep .editorconfig in sync with .gitattributes 2025-02-01 10:09:45 +01:00
.git-blame-ignore-revs Add commit 9e345415bc to .git-blame-ignore-revs. 2025-07-01 14:30:16 -05:00
.gitattributes Add script to keep .editorconfig in sync with .gitattributes 2025-02-01 10:09:45 +01:00
.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 oauth: Run Autoconf tests with correct compiler flags 2025-07-11 10:06:41 -07:00
configure.ac aio: Combine io_uring memory mappings, if supported 2025-07-07 22:57:07 -04:00
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 aio: Combine io_uring memory mappings, if supported 2025-07-07 22:57:07 -04:00
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/.