database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-20 15:22:23 +03:00
Code Activity

Improve the representation of FOR UPDATE/FOR SHARE so that we can

Browse Source 
support both FOR UPDATE and FOR SHARE in one command, as well as both
NOWAIT and normal WAIT behavior.  The more general code is actually
simpler and cleaner.
This commit is contained in:
Tom Lane
2006-04-30 18:30:40 +00:00
parent 931bfc9664
commit 986085a7f0
29 changed files with 320 additions and 245 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
doc/src/sgml/ref/select.sgml
View File

@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.90 2005/11/01 21:09:51 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.91 2006/04/30 18:30:38 tgl Exp $
PostgreSQL documentation
-->
@ -30,7 +30,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
[ ORDER BY <replaceable class="parameter">expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [, ...] ]
[ LIMIT { <replaceable class="parameter">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="parameter">start</replaceable> ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] [...] ]
where <replaceable class="parameter">from_item</replaceable> can be one of:
@ -142,8 +142,8 @@ where <replaceable class="parameter">from_item</replaceable> can be one of:
<listitem>
<para>
If the <literal>FOR UPDATE</literal> or <literal>FOR SHARE</literal>
clause is specified, the
If <literal>FOR UPDATE</literal> or <literal>FOR SHARE</literal>
is specified, the
<command>SELECT</command> statement locks the selected rows
against concurrent updates. (See <xref linkend="sql-for-update-share"
endterm="sql-for-update-share-title"> below.)
@ -852,19 +852,27 @@ FOR SHARE [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ]
from performing <command>SELECT FOR SHARE</command>.
</para>
<para>
It is currently not allowed for a single <command>SELECT</command>
statement to include both <literal>FOR UPDATE</literal> and
<literal>FOR SHARE</literal>, nor can different parts of the statement use
both <literal>NOWAIT</> and normal waiting mode.
</para>
<para>
If specific tables are named in <literal>FOR UPDATE</literal>
or <literal>FOR SHARE</literal>,
then only rows coming from those tables are locked; any other
tables used in the <command>SELECT</command> are simply read as
usual.
usual. A <literal>FOR UPDATE</literal> or <literal>FOR SHARE</literal>
clause without a table list affects all tables used in the command.
If <literal>FOR UPDATE</literal> or <literal>FOR SHARE</literal> is
applied to a view or sub-query, it affects all tables used in
the view or sub-query.
</para>
<para>
Multiple <literal>FOR UPDATE</literal> and <literal>FOR SHARE</literal>
clauses can be written if it is necessary to specify different locking
behavior for different tables. If the same table is mentioned (or
implicitly affected) by both <literal>FOR UPDATE</literal> and
<literal>FOR SHARE</literal> clauses, then it is processed as
<literal>FOR UPDATE</literal>. Similarly, a table is processed
as <literal>NOWAIT</> if that is specified in any of the clauses
affecting it.
</para>
<para>

4
doc/src/sgml/ref/select_into.sgml
View File

@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select_into.sgml,v 1.36 2005/08/01 20:31:04 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select_into.sgml,v 1.37 2006/04/30 18:30:38 tgl Exp $
PostgreSQL documentation
-->
@ -31,7 +31,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="PARAMETER">expression</replac
[ ORDER BY <replaceable class="PARAMETER">expression</replaceable> [ ASC | DESC | USING <replaceable class="PARAMETER">operator</replaceable> ] [, ...] ]
[ LIMIT { <replaceable class="PARAMETER">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="PARAMETER">start</replaceable> ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] [...] ]
</synopsis>
</refsynopsisdiv>

4
doc/src/sgml/sql.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/sql.sgml,v 1.39 2006/03/10 19:10:49 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/sql.sgml,v 1.40 2006/04/30 18:30:38 tgl Exp $ -->
<chapter id="sql-intro">
<title>SQL</title>
@ -863,7 +863,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="PARAMETER">expression</replac
[ ORDER BY <replaceable class="PARAMETER">expression</replaceable> [ ASC | DESC | USING <replaceable class="PARAMETER">operator</replaceable> ] [, ...] ]
[ LIMIT { <replaceable class="PARAMETER">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="PARAMETER">start</replaceable> ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] [...] ]
</synopsis>
</para>