diff options
Diffstat (limited to 'doc/src/sgml/ref/lock.sgml')
| -rw-r--r-- | doc/src/sgml/ref/lock.sgml | 79 |
1 files changed, 53 insertions, 26 deletions
diff --git a/doc/src/sgml/ref/lock.sgml b/doc/src/sgml/ref/lock.sgml index bffbb7c23d4..d576890acb9 100644 --- a/doc/src/sgml/ref/lock.sgml +++ b/doc/src/sgml/ref/lock.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/lock.sgml,v 1.23 2000/12/25 23:15:26 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/lock.sgml,v 1.24 2001/07/09 22:18:33 tgl Exp $ Postgres documentation --> @@ -20,12 +20,16 @@ Postgres documentation </refnamediv> <refsynopsisdiv> <refsynopsisdivinfo> - <date>1999-07-20</date> + <date>2001-07-09</date> </refsynopsisdivinfo> <synopsis> LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> -LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN [ ROW | ACCESS ] { SHARE | EXCLUSIVE } MODE -LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EXCLUSIVE MODE +LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN <replaceable class="PARAMETER">lockmode</replaceable> MODE + +where <replaceable class="PARAMETER">lockmode</replaceable> is one of: + + ACCESS SHARE | ROW SHARE | ROW EXCLUSIVE | SHARE UPDATE EXCLUSIVE | + SHARE | SHARE ROW EXCLUSIVE | EXCLUSIVE | ACCESS EXCLUSIVE </synopsis> <refsect2 id="R2-SQL-LOCK-1"> @@ -33,7 +37,6 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX <date>1999-06-09</date> </refsect2info> - <title> Inputs </title> @@ -62,7 +65,7 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX This is the least restrictive lock mode. It conflicts only with ACCESS EXCLUSIVE mode. It is used to protect a table from being modified by concurrent <command>ALTER TABLE</command>, - <command>DROP TABLE</command> and <command>VACUUM</command> + <command>DROP TABLE</command> and <command>VACUUM FULL</command> commands. </para> </listitem> @@ -103,6 +106,25 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX </varlistentry> <varlistentry> + <term>SHARE UPDATE EXCLUSIVE MODE</term> + <listitem> + <note> + <para> + Automatically acquired by <command>VACUUM</command> (without + <option>FULL</option>). + </para> + </note> + + <para> + Conflicts with SHARE UPDATE EXCLUSIVE, SHARE, SHARE ROW EXCLUSIVE, + EXCLUSIVE and + ACCESS EXCLUSIVE modes. This mode protects a table against + concurrent schema changes and VACUUMs. + </para> + </listitem> + </varlistentry> + + <varlistentry> <term>SHARE MODE</term> <listitem> <note> @@ -113,9 +135,10 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX </note> <para> - Conflicts with ROW EXCLUSIVE, SHARE ROW EXCLUSIVE, EXCLUSIVE and + Conflicts with ROW EXCLUSIVE, SHARE UPDATE EXCLUSIVE, + SHARE ROW EXCLUSIVE, EXCLUSIVE and ACCESS EXCLUSIVE modes. This mode protects a table against - concurrent updates. + concurrent data updates. </para> </listitem> </varlistentry> @@ -125,14 +148,14 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX <listitem> <note> <para> - This is like EXCLUSIVE MODE, but allows SHARE ROW locks + This is like EXCLUSIVE MODE, but allows ROW SHARE locks by others. </para> </note> <para> - Conflicts with ROW EXCLUSIVE, SHARE, SHARE ROW EXCLUSIVE, - EXCLUSIVE and ACCESS EXCLUSIVE modes. + Conflicts with ROW EXCLUSIVE, SHARE UPDATE EXCLUSIVE, SHARE, + SHARE ROW EXCLUSIVE, EXCLUSIVE and ACCESS EXCLUSIVE modes. </para> </listitem> </varlistentry> @@ -149,7 +172,8 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX </note> <para> - Conflicts with ROW SHARE, ROW EXCLUSIVE, SHARE, SHARE ROW EXCLUSIVE, + Conflicts with ROW SHARE, ROW EXCLUSIVE, SHARE UPDATE EXCLUSIVE, + SHARE, SHARE ROW EXCLUSIVE, EXCLUSIVE and ACCESS EXCLUSIVE modes. </para> </listitem> @@ -161,9 +185,10 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX <note> <para> Automatically acquired by <command>ALTER TABLE</command>, - <command>DROP TABLE</command>, <command>VACUUM</command> statements. - This is the most restrictive lock mode which conflicts with all other - lock modes and protects a locked table from any concurrent operations. + <command>DROP TABLE</command>, <command>VACUUM FULL</command> + statements. + This is the most restrictive lock mode which + protects a locked table from any concurrent operations. </para> </note> @@ -174,6 +199,10 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX lock mode option). </para> </note> + + <para> + Conflicts with all lock modes. + </para> </listitem> </varlistentry> </variablelist> @@ -241,7 +270,11 @@ ERROR <replaceable class="PARAMETER">name</replaceable>: Table does not exist. <term>EXCLUSIVE</term> <listitem> <para> - Exclusive lock that prevents other locks from being granted. + An exclusive lock prevents other locks of the same type from being + granted. (Note: ROW EXCLUSIVE mode does not follow this naming + convention perfectly, since it is shared at the level of the table; + it is exclusive only with respect to specific rows that are being + updated.) </para> </listitem> </varlistentry> @@ -250,7 +283,8 @@ ERROR <replaceable class="PARAMETER">name</replaceable>: Table does not exist. <term>SHARE</term> <listitem> <para> - Allows others to share lock. Prevents EXCLUSIVE locks. + A shared lock allows others to also hold the same type of lock, + but prevents the corresponding EXCLUSIVE lock from being granted. </para> </listitem> </varlistentry> @@ -273,13 +307,6 @@ ERROR <replaceable class="PARAMETER">name</replaceable>: Table does not exist. </listitem> </varlistentry> </variablelist> - - <note> - <para> - If EXCLUSIVE or SHARE are not specified, EXCLUSIVE is assumed. - Locks exist for the duration of the transaction. - </para> - </note> </para> <para> @@ -370,8 +397,8 @@ ERROR <replaceable class="PARAMETER">name</replaceable>: Table does not exist. </para> <para> - Except for ACCESS SHARE/EXCLUSIVE lock modes, all other - <productname>Postgres</productname> lock modes and the + Except for ACCESS SHARE, ACCESS EXCLUSIVE, and SHARE UPDATE EXCLUSIVE lock + modes, the <productname>Postgres</productname> lock modes and the <command>LOCK TABLE</command> syntax are compatible with those present in <productname>Oracle</productname>. </para> |