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Remove old claim that ExclusiveLock is sometimes taken on system catalogs.

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We used to do that on pg_listener, but pg_listener is no more.

Also add a bit more documentation for ShareRowExclusive mode.
This commit is contained in:
Tom Lane 2011-01-25 18:39:01 -05:00
parent 558d1c95ae
commit 5042d16d12
1 changed files with 4 additions and 3 deletions
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7
doc/src/sgml/mvcc.sgml
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@ -692,6 +692,8 @@ SELECT SUM(value) FROM mytab WHERE class = 2;
<literal>SHARE</literal>, <literal>SHARE ROW
EXCLUSIVE</literal>, <literal>EXCLUSIVE</literal>, and
<literal>ACCESS EXCLUSIVE</literal> lock modes.
This mode protects a table against concurrent data changes, and
is self-exclusive so that only one session can hold it at a time.
</para>
<para>
@ -719,9 +721,8 @@ SELECT SUM(value) FROM mytab WHERE class = 2;
</para>
<para>
This lock mode is not automatically acquired on user tables by any
<productname>PostgreSQL</productname> command. However it is
acquired on certain system catalogs in some operations.
This lock mode is not automatically acquired on tables by any
<productname>PostgreSQL</productname> command.
</para>
</listitem>
</varlistentry>