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* [PATCH v27 5/5] Doc: Add Collation Versions section.
@ 2020-03-11 02:01 Thomas Munro <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: Thomas Munro @ 2020-03-11 02:01 UTC (permalink / raw)
Supply a brief introduction to collation version concepts.
Author: Thomas Munro <[email protected]>
Reviewed-by: Julien Rouhaud <[email protected]>
Discussion: https://postgr.es/m/CAEepm%3D0uEQCpfq_%2BLYFBdArCe4Ot98t1aR4eYiYTe%3DyavQygiQ%40mail.gmail.com
---
doc/src/sgml/charset.sgml | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/doc/src/sgml/charset.sgml b/doc/src/sgml/charset.sgml
index 4b4563c5b9..12a82ff18c 100644
--- a/doc/src/sgml/charset.sgml
+++ b/doc/src/sgml/charset.sgml
@@ -948,6 +948,41 @@ CREATE COLLATION ignore_accents (provider = icu, locale = 'und-u-ks-level1-kc-tr
</tip>
</sect3>
</sect2>
+
+ <sect2 id="collation-versions">
+ <title>Collation Versions</title>
+
+ <para>
+ The ordering defined by a collation is not necessarily fixed over time.
+ If a collation changes for any reason, persistent data structures such as
+ b-trees that depend on a stable ordering of text might be corrupted.
+ <productname>PostgreSQL</productname> defends against this by recording
+ the current version of each referenced collation for any index that
+ depends on it in the
+ <link linkend="catalog-pg-depend"><structname>pg_depend</structname></link>
+ catalog, if the collation provider makes it available. If the provider
+ later begins to report a different version, a warning will be issued
+ when the index is accessed, until either the <xref linkend="sql-reindex"/>
+ or the <xref linkend="sql-alterindex"/> command is used to update the
+ version.
+ </para>
+ <para>
+ Version information is available for collations from the
+ <literal>icu</literal> provider on all operating systems. For the
+ <literal>libc</literal> provider, versions are currently only available
+ on systems using the GNU C library (most Linux systems).
+ </para>
+
+ <note>
+ <para>
+ When using the GNU C library for collations, the C library's version
+ is used as a proxy for the collation version. Many Linux distributions
+ change collation definitions only when upgrading the C library, but this
+ approach is imperfect as maintainers are free to back-port newer
+ collation definitions to older C library releases.
+ </para>
+ </note>
+ </sect2>
</sect1>
<sect1 id="multibyte">
--
2.20.1
--o56keubw4jpehgac--
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: using extended statistics to improve join estimates
@ 2022-01-19 10:18 Julien Rouhaud <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: Julien Rouhaud @ 2022-01-19 10:18 UTC (permalink / raw)
To: Andres Freund <[email protected]>; +Cc: Tomas Vondra <[email protected]>; Justin Pryzby <[email protected]>; pgsql-hackers
Hi,
On Tue, Jan 04, 2022 at 03:55:50PM -0800, Andres Freund wrote:
> On 2022-01-01 18:21:06 +0100, Tomas Vondra wrote:
> > Here's an updated patch, rebased and fixing a couple typos reported by
> > Justin Pryzby directly.
>
> FWIW, cfbot reports a few compiler warnings:
Also the patch doesn't apply anymore:
http://cfbot.cputube.org/patch_36_3055.log
=== Applying patches on top of PostgreSQL commit ID 74527c3e022d3ace648340b79a6ddec3419f6732 ===
=== applying patch ./0001-Estimate-joins-using-extended-statistics-20220101.patch
patching file src/backend/optimizer/path/clausesel.c
patching file src/backend/statistics/extended_stats.c
Hunk #1 FAILED at 30.
Hunk #2 succeeded at 102 (offset 1 line).
Hunk #3 succeeded at 2619 (offset 9 lines).
1 out of 3 hunks FAILED -- saving rejects to file src/backend/statistics/extended_stats.c.rej
^ permalink raw reply [nested|flat] 2+ messages in thread
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2020-03-11 02:01 [PATCH v27 5/5] Doc: Add Collation Versions section. Thomas Munro <[email protected]>
2022-01-19 10:18 Re: using extended statistics to improve join estimates Julien Rouhaud <[email protected]>
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