Author: jstephens
Date: 2006-05-24 02:19:00 +0200 (Wed, 24 May 2006)
New Revision: 2180
Log:
Documenting Event Scheduler bugfixes/feature changes:
Bug #16428, Bug #17619, Bug #19264
Change in behaviour of event scheduler thread / @@global.event_scheduler
variable / --event-scheduler startup option.
Modified:
trunk/refman-5.1/events.xml
trunk/refman-common/news-5.1.xml
Modified: trunk/refman-5.1/events.xml
===================================================================
--- trunk/refman-5.1/events.xml 2006-05-23 20:45:36 UTC (rev 2179)
+++ trunk/refman-5.1/events.xml 2006-05-24 00:19:00 UTC (rev 2180)
@@ -201,46 +201,69 @@
</itemizedlist>
<para>
- MySQL 5.1.6 introduces a global variable
- <literal>event_scheduler</literal> which determines whether the
- Event scheduler is enabled for the server. This variable defaults
- to <literal>OFF</literal> or <literal>0</literal>, meaning that
- event scheduling is not available:
+ The global variable <literal>event_scheduler</literal> determines
+ whether the Event Scheduler is enabled on the server. Beginning
+ with MySQL 5.1.11, it can have one of these 3 values, which affect
+ event scheduling as follows:
</para>
+
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>0</literal>: Event scheduling is OFF: The event
+ scheduler thread does not run, and no scheduled events are
+ executed. The <literal>event_scheduler</literal> variable
+ cannot be set to this value while the server is running;
+ instead, to turn off event scheduling altogether, you must
+ start the server with
+ <literal><option>--event-scheduler</option>=0</literal> or
+ <literal><option>--event-scheduler</option>=OFF</literal>.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <literal>1</literal>: The event scheduler is ON; the event
+ scheduler thread runs and executes all scheduled events.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <literal>2</literal>: The event scheduler is SUSPENDED; the
+ event scheduler thread runs, but it does not execute any
+ scheduled events. This is the default value for
+ <literal>event_scheduler</literal>.
+ </para>
+ </listitem>
+ </itemizedlist>
+
+ <para>
+ Provided that the event scheduler thread has not been deactivated
+ by starting the server with <option>--event-scheduler=0</option>,
+ you can enable the execution of scheduled events by issuing either
+ of the following two statements:
+ </para>
<programlisting>
-mysql> <userinput>SHOW GLOBAL VARIABLES LIKE 'event%'</userinput>;
-+-----------------+-------+
-| Variable_name | Value |
-+-----------------+-------+
-| event_scheduler | OFF |
-+-----------------+-------+
-1 row in set (0.01 sec)
-
-mysql> <userinput>SELECT @@event_scheduler;</userinput>
-+-------------------+
-| @@event_scheduler |
-+-------------------+
-| 0 |
-+-------------------+
-1 row in set (0.00 sec)
+SET GLOBAL event_scheduler = 1;
</programlisting>
<para>
- In order to enable event scheduling, you must first issue one of
- these statements:
+ or
</para>
<programlisting>
-SET GLOBAL event_scheduler = ON;
+SET @@global.event_scheduler = 1;
</programlisting>
-
+
<para>
- or
+ If event scheduling is enabled, you can disable it by issuing
+ either one of these two statements:
</para>
<programlisting>
-SET GLOBAL event_scheduler = 1;
+SET GLOBAL event_scheduler = 2;
</programlisting>
<para>
@@ -248,41 +271,67 @@
</para>
<programlisting>
-SET @@global.event_scheduler = ON;
+SET @@global.event_scheduler = 2;
</programlisting>
-
+
<para>
- or
+ <emphasis role="bold">Important</emphasis>: Once the server
+ has been started with the event scheduler thread deactivated,
+ the thread cannot be activated — that is, if the server
+ was started with <option>--event-scheduler=0</option>, then
+ <literal>event_scheduler</literal> cannot be set to
+ <literal>1</literal> or <literal>2</literal> — without
+ restarting <command>mysqld</command>. Similarly, if the server
+ was started with the event scheduler thread running —
+ that is, with <option>--event-scheduler=1</option> or
+ <option>--event-schedule=2</option> — you cannot stop the
+ event scheduler thread by issuing <literal>SET
+ @@global.event_scheduler = 0;</literal>. Attempting to start or
+ stop the event scheduler thread while the server is running causes
+ an error, as shown here:
</para>
+
+<programlisting>
+mysql> <userinput>SELECT @@global.event_scheduler;</userinput>
++--------------------------+
+| @@global.event_scheduler |
++--------------------------+
+| 2 |
++--------------------------+
+1 row in set (0.00 sec)
-<programlisting>
-SET @@global.event_scheduler = 1;
+mysql> <userinput>SET @@global.event_scheduler = 0;</userinput>
+<errortext>ERROR 1231 (42000): Variable 'event_scheduler' can't be set to the value of '0'</errortext>
+mysql> <userinput>SET @@global.event_scheduler = 1;</userinput>
+Query OK, 0 rows affected (0.01 sec)
</programlisting>
<para>
- <emphasis role="bold">Note</emphasis>: You can issue
- event-manipulation statements when
- <literal>event_scheduler</literal> is set to
- <literal>OFF</literal> or <literal>0</literal>. No warnings or
- errors are generated in such cases (so long as the statements are
- themselves valid). However, scheduled events cannot execute until
- this variable is set to <literal>ON</literal> or
- <literal>1</literal>. (Once this has been done, all events whose
- scheduling conditions are met become active.)
+ Since <literal>event_scheduler</literal> is a global variable, you
+ must have the <literal>SUPER</literal> privilege to set its value.
</para>
<para>
- <emphasis role="bold">Note</emphasis>: Since
- <literal>event_scheduler</literal> is a global variable, you must
- have the <literal>SUPER</literal> privilege to set its value.
+ <emphasis role="bold">Note</emphasis>: You can issue
+ event-manipulation statements when
+ <literal>event_scheduler</literal> is set to <literal>0</literal>
+ or <literal>2</literal>. No warnings or errors are generated in
+ such cases (provided that the statements are themselves valid).
+ However, scheduled events cannot execute until this variable is
+ set to <literal>1</literal>. Once this has been done, the event
+ scheduler thread executes all events whose scheduling conditions
+ are satisfied.
</para>
-
+
<para>
- You can also enable event scheduling by starting
- <command>mysqld</command> with
- <option>--event_scheduler=1</option> or more simply
- <option>--event_scheduler</option>. (<literal>1</literal> is the
- default value in this case.)
+ <emphasis role="bold">Note</emphasis>: Prior to MySQL 5.1.11,
+ <literal>event_scheduler</literal> could take one of only the 2
+ values <literal>0</literal>|<literal>OFF</literal> or
+ <literal>1</literal>|<literal>ON</literal>, the default value
+ being <literal>0</literal>|<literal>OFF</literal>. It was also
+ possible to start and stop the event scheduler thread while the
+ MySQL server was running. For information concerning the reasons
+ for this change in behaviour, see Bug #17619.
</para>
<para>
Modified: trunk/refman-common/news-5.1.xml
===================================================================
--- trunk/refman-common/news-5.1.xml 2006-05-23 20:45:36 UTC (rev 2179)
+++ trunk/refman-common/news-5.1.xml 2006-05-24 00:19:00 UTC (rev 2180)
@@ -57,6 +57,23 @@
</para>
<itemizedlist>
+
+ <listitem>
+ <para>
+ <emphasis role="bold">Incompatible change</emphasis>: The
+ Event Scheduler can now be in one of three states (on, off, or
+ the new suspended state). In addition, due to the fact that
+ <literal>SET GLOBAL event_scheduler;</literal> now acts in a
+ synchronous rather than asynchronous manner, the Event
+ Scheduler thread can be no longer be activated or deactivated
+ at run time. (Bug #17619)
+ </para>
+
+ <para>
+ For more information regarding these changes, see
+ <xref linkend="events-overview"/>.
+ </para>
+ </listitem>
<listitem>
<para>
@@ -135,6 +152,20 @@
<listitem>
<para>
+ Simultaneous scheduled events whose actions conflicted with
+ one another could crash the server. (Bug #16428)
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ In was not possible to invoke a stored routine containing
+ dynamic SQL from a scheduled event. (Bug #19264)
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
<literal>NDB Cluster</literal>: Running <literal>ALL
START</literal> in the <literal>NDB</literal> management
client or restarting multiple nodes simultaneously could under
| Thread |
|---|
| • svn commit - mysqldoc@docsrva: r2180 - in trunk: refman-5.1 refman-common | jon | 24 May |
