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Noah Misch bdfb372280 Fix SUBSTRING() for toasted multibyte characters. 
Commit 1e7fe06c10 changed
pg_mbstrlen_with_len() to ereport(ERROR) if the input ends in an
incomplete character.  Most callers want that.  text_substring() does
not.  It detoasts the most bytes it could possibly need to get the
requested number of characters.  For example, to extract up to 2 chars
from UTF8, it needs to detoast 8 bytes.  In a string of 3-byte UTF8
chars, 8 bytes spans 2 complete chars and 1 partial char.

Fix this by replacing this pg_mbstrlen_with_len() call with a string
traversal that differs by stopping upon finding as many chars as the
substring could need.  This also makes SUBSTRING() stop raising an
encoding error if the incomplete char is past the end of the substring.
This is consistent with the general philosophy of the above commit,
which was to raise errors on a just-in-time basis.  Before the above
commit, SUBSTRING() never raised an encoding error.

SUBSTRING() has long been detoasting enough for one more char than
needed, because it did not distinguish exclusive and inclusive end
position.  For avoidance of doubt, stop detoasting extra.

Back-patch to v14, like the above commit.  For applications using
SUBSTRING() on non-ASCII column values, consider applying this to your
copy of any of the February 12, 2026 releases.

Reported-by: SATŌ Kentarō <ranvis@gmail.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Bug: #19406
Discussion: https://postgr.es/m/19406-9867fddddd724fca@postgresql.org
Backpatch-through: 14
2026-02-14 12:16:20 -08:00
config Don't put library-supplied -L/-I switches before user-supplied ones. 2025-07-29 15:17:41 -04:00
contrib Further stabilize a postgres_fdw test case. 2026-02-11 11:03:01 -05:00
doc doc: Mention all SELECT privileges required by INSERT ... ON CONFLICT. 2026-02-11 10:53:00 +00:00
src Fix SUBSTRING() for toasted multibyte characters. 2026-02-14 12:16:20 -08:00
.abi-compliance-history Placate ABI checker. 2026-02-07 11:50:35 +13:00
.cirrus.star ci: Simplify ci-os-only handling 2025-08-14 12:03:27 -04:00
.cirrus.tasks.yml Fix typo 2026-01-07 15:49:00 +01:00
.cirrus.yml ci: Per-repo configuration for manually trigger tasks 2025-08-14 11:33:50 -04:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add .editorconfig 2019-12-18 09:13:13 +01:00
.git-blame-ignore-revs Add previous commit to .git-blame-ignore-revs. 2025-10-21 10:02:19 -05:00
.gitattributes Fix git whitespace warning 2025-08-15 10:31:52 +02:00
.gitignore Update top-level .gitignore. 2022-12-04 15:23:00 -05:00
aclocal.m4 autoconf: Move export_dynamic determination to configure 2022-12-06 18:55:28 -08:00
configure Stamp 16.12. 2026-02-09 16:53:53 -05:00
configure.ac Stamp 16.12. 2026-02-09 16:53:53 -05:00
COPYRIGHT Update copyright for 2026 2026-01-01 13:24:10 -05:00
GNUmakefile.in Integrate pg_bsd_indent into our build/test infrastructure. 2023-02-12 12:22:21 -05:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Dynamically find correct installation docs in Makefile. 2022-01-19 14:48:25 +01:00
meson.build Stamp 16.12. 2026-02-09 16:53:53 -05:00
meson_options.txt meson: Attach colon to keyword argument 2023-06-29 12:53:41 +02:00
README Canonicalize some URLs 2020-02-10 20:47:50 +01:00
README.git Canonicalize some URLs 2020-02-10 20:47:50 +01:00

README 

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.

PostgreSQL has many language interfaces, many of which are listed here:

	https://www.postgresql.org/download/

See the file INSTALL for instructions on how to build and install
PostgreSQL.  That file also lists supported operating systems and
hardware platforms and contains information regarding any other
software packages that are required to build or run the PostgreSQL
system.  Copyright and license information can be found in the
file COPYRIGHT.  A comprehensive documentation set is included in this
distribution; it can be read as described in the installation
instructions.

The latest version of this software may be obtained at
https://www.postgresql.org/download/.  For more information look at our
web site located at https://www.postgresql.org/.