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authorBruce Momjian <bruce@momjian.us>2000-03-23 21:38:58 +0000
committerBruce Momjian <bruce@momjian.us>2000-03-23 21:38:58 +0000
commit4ddc50dffa279b2c0147474f7b323de99a6b7aa7 (patch)
treecce7be19279093abf469c128b054ff7f17d46227 /doc/src/sgml/ref
parentb2d867fb086c2b8c504387d177b80b9d09b76370 (diff)
Hmm, absolute pathnames for the copy makes sense. I'll whip up that
patch in a second. Should be sufficent to just make sure the first character is a '/', right? Ross J. Reedstrom
Diffstat (limited to 'doc/src/sgml/ref')
-rw-r--r--doc/src/sgml/ref/lock.sgml91
1 files changed, 79 insertions, 12 deletions
diff --git a/doc/src/sgml/ref/lock.sgml b/doc/src/sgml/ref/lock.sgml
index da753b9bb38..06dc405b31c 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 1.14 1999/10/01 15:26:29 thomas Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/lock.sgml,v 1.15 2000/03/23 21:38:57 momjian Exp $
Postgres documentation
-->
@@ -32,6 +32,70 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX
<refsect2info>
<date>1999-06-09</date>
</refsect2info>
+
+ <title>
+ Terms
+ </title>
+ <para>
+ <variablelist>
+ <varlistentry>
+ <term>EXCLUSIVE</term>
+ <listitem>
+ <para>
+ Exclusive lock that prevents other locks from being granted.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <variablelist>
+ <varlistentry>
+ <term>SHARE</term>
+ <listitem>
+ <para>
+ Allows others to share lock. Prevents EXCLUSIVE locks.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <variablelist>
+ <varlistentry>
+ <term>ACCESS</term>
+ <listitem>
+ <para>
+ Locks table schema.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <variablelist>
+ <varlistentry>
+ <term>ROW</term>
+ <listitem>
+ <para>
+ Locks individual rows.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <variablelist>
+ <varlistentry>
+ <term>Notes</term>
+ <listitem>
+ <para>
+ If EXCLUSIVE or SHARE are not speicified, EXCLUSIVE is assumed.
+ If ROW or ACCESS is not specified, the entire table is locked
+ for the duration of the transaction.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ </para>
+
<title>
Inputs
</title>
@@ -53,17 +117,17 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX
<note>
<para>
This lock mode is acquired automatically over tables being queried.
- <productname>Postgres</productname> releases automatically acquired
- ACCESS SHARE locks after the statement is done.
+ This lock is released automatically after the statement completes.
+ It does not remain for the duration of the transaction.
</para>
</note>
<para>
This is the least restrictive lock mode which conflicts only with
ACCESS EXCLUSIVE mode. It is intended to protect a table being
- queried from concurrent <command>ALTER TABLE</command>,
+ modified by concurrent <command>ALTER TABLE</command>,
<command>DROP TABLE</command> and <command>VACUUM</command>
- statements over the same table.
+ commands.
</para>
</listitem>
</varlistentry>
@@ -74,6 +138,8 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX
<note>
<para>
Automatically acquired by any <command>SELECT FOR UPDATE</command> statement.
+ While it is a SHARE lock, there is the intention to later upgrade
+ this to an EXCLUSIVE lock.
</para>
</note>
@@ -90,7 +156,7 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX
<para>
Automatically acquired by any <command>UPDATE</command>,
<command>DELETE</command>, <command>INSERT</command> statement.
- </para>
+ </para>
</note>
<para>
@@ -107,6 +173,7 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX
<note>
<para>
Automatically acquired by any <command>CREATE INDEX</command> statement.
+ Share-locks entire table.
</para>
</note>
@@ -123,10 +190,10 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX
<listitem>
<para>
- Conflicts with ROW EXCLUSIVE, SHARE, SHARE ROW EXCLUSIVE,
- EXCLUSIVE and ACCESS EXCLUSIVE modes. This mode is more
- restrictive than SHARE mode because of only one transaction
- at time can hold this lock.
+ This is like an EXCLUSIVE lock, but allows SHARE ROW locks
+ by others.
+ Conflicts with ROW EXCLUSIVE, SHARE, SHARE ROW EXCLUSIVE,
+ EXCLUSIVE and ACCESS EXCLUSIVE modes.
</para>
</listitem>
</varlistentry>
@@ -139,7 +206,7 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX
Conflicts with ROW SHARE, ROW EXCLUSIVE, SHARE, SHARE ROW EXCLUSIVE,
EXCLUSIVE and ACCESS EXCLUSIVE modes. This mode is yet more
restrictive than that of SHARE ROW EXCLUSIVE; it blocks all concurrent
- SELECT FOR UPDATE queries.
+ SHARE ROW/SELECT FOR UPDATE queries.
</para>
</listitem>
</varlistentry>
@@ -149,7 +216,7 @@ LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN SHARE ROW EX
<listitem>
<note>
<para>
- Automatically acquired by <command>ALTER TABLE</command>,
+ Automatically acquired by <command>ALTER TABLE</command>,
<command>DROP TABLE</command>, <command>VACUUM</command> statements.
</para>
</note>