From 70de0abdb7c6dce24dd5c0e276708ca7c534f99f Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter_e@gmx.net>
Date: Mon, 30 Jul 2018 22:01:04 +0200
Subject: [PATCH] doc: Improve CREATE COLLATION locking documentation
Move out of the concurrency control chapter, where mostly only user
table locks are discussed, and move to CREATE COLLATION reference page.
Author: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Author: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
---
doc/src/sgml/mvcc.sgml | 3 +--
doc/src/sgml/ref/create_collation.sgml | 7 +++++++
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/doc/src/sgml/mvcc.sgml b/doc/src/sgml/mvcc.sgml
index 24613e3c754..73934e5cf37 100644
--- a/doc/src/sgml/mvcc.sgml
+++ b/doc/src/sgml/mvcc.sgml
@@ -970,8 +970,7 @@ ERROR: could not serialize access due to read/write dependencies among transact
</para>
<para>
- Acquired by <command>CREATE COLLATION</command>,
- <command>CREATE TRIGGER</command>, and many forms of
+ Acquired by <command>CREATE TRIGGER</command> and many forms of
<command>ALTER TABLE</command> (see <xref linkend="sql-altertable"/>).
</para>
</listitem>
diff --git a/doc/src/sgml/ref/create_collation.sgml b/doc/src/sgml/ref/create_collation.sgml
index 5bc9af5499e..038797fce11 100644
--- a/doc/src/sgml/ref/create_collation.sgml
+++ b/doc/src/sgml/ref/create_collation.sgml
@@ -162,6 +162,13 @@ CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> FROM <replace
<refsect1 id="sql-createcollation-notes">
<title>Notes</title>
+ <para>
+ <command>CREATE COLLATION</command> takes a <literal>SHARE ROW
+ EXCLUSIVE</literal> lock, which is self-conflicting, on the
+ <structname>pg_collation</structname> system catalog, so only one
+ <command>CREATE COLLATION</command> command can run at a time.
+ </para>
+
<para>
Use <command>DROP COLLATION</command> to remove user-defined collations.
</para>
--
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