Comments on: SHOW STATUS WHERE…. http://www.pythian.com/news/1222/show-status-where/ News and views from Pythian DBAs Fri, 10 Feb 2012 13:01:25 +0000 hourly 1 http://wordpress.org/?v=3.0.4 By: Artículos destacados de Septiembre | cambrico.net http://www.pythian.com/news/1222/show-status-where/#comment-287150 Artículos destacados de Septiembre | cambrico.net Mon, 06 Oct 2008 18:30:54 +0000 http://www.pythian.com/blogs/1222/show-status-where#comment-287150 [...] del SHOW STATUS WHERE en Pythian (en [...] [...] del SHOW STATUS WHERE en Pythian (en [...]

]]> By: Sheeri Cabral http://www.pythian.com/news/1222/show-status-where/#comment-278495 Sheeri Cabral Wed, 17 Sep 2008 19:02:25 +0000 http://www.pythian.com/blogs/1222/show-status-where#comment-278495 Brian -- Thanx for the clarification! I knew other systems had tables, but 5.1 isn't in widespread use yet, so I wasn't exposed to this. Brian –

Thanx for the clarification! I knew other systems had tables, but 5.1 isn’t in widespread use yet, so I wasn’t exposed to this.

]]> By: Brian Papantonio http://www.pythian.com/news/1222/show-status-where/#comment-278474 Brian Papantonio Wed, 17 Sep 2008 17:59:02 +0000 http://www.pythian.com/blogs/1222/show-status-where#comment-278474 He meant to use the information_schema.global/session_status tables. They aren't available until MySQL 5.1.12, but other DBMSs have had them for a while. http://dev.mysql.com/doc/refman/5.1/en/status-table.html There's really no advantage over using SHOW STATUS ... WHERE since you aren't going to join this table into another table. It will probably be even slower. He meant to use the information_schema.global/session_status tables. They aren’t available until MySQL 5.1.12, but other DBMSs have had them for a while.

http://dev.mysql.com/doc/refman/5.1/en/status-table.html

There’s really no advantage over using SHOW STATUS … WHERE since you aren’t going to join this table into another table. It will probably be even slower.

]]> By: Sheeri Cabral http://www.pythian.com/news/1222/show-status-where/#comment-277348 Sheeri Cabral Mon, 15 Sep 2008 13:15:07 +0000 http://www.pythian.com/blogs/1222/show-status-where#comment-277348 p -- A view definition statement can only take a SELECT statement, so if you mean we should do CREATE VIEW v_status AS SHOW STATUS; then that won't work. Or did you have something else in mind? p –

A view definition statement can only take a SELECT statement, so if you mean we should do

CREATE VIEW v_status AS SHOW STATUS;

then that won’t work. Or did you have something else in mind?

]]> By: p http://www.pythian.com/news/1222/show-status-where/#comment-276642 p Sat, 13 Sep 2008 22:38:32 +0000 http://www.pythian.com/blogs/1222/show-status-where#comment-276642 No need for like or where, simply implement that as an information_schema view, and you'll automagically have a standard synthax which can be handled also by reporting tools. Too difficult? No need for like or where, simply implement that as an information_schema view, and you’ll automagically have a standard synthax which can be handled also by reporting tools.
Too difficult?

]]> By: Sheeri Cabral http://www.pythian.com/news/1222/show-status-where/#comment-276552 Sheeri Cabral Sat, 13 Sep 2008 17:03:12 +0000 http://www.pythian.com/blogs/1222/show-status-where#comment-276552 Thanx! This is very important information, so I'll show some examples: mysql> show global status like 'Handler_read_rnd_next'; +-----------------------+-------+ | Variable_name | Value | +-----------------------+-------+ | Handler_read_rnd_next | 13010 | +-----------------------+-------+ 1 row in set (0.00 sec) mysql> show global status where Variable_name='Handler_read_rnd_next'; +-----------------------+-------+ | Variable_name | Value | +-----------------------+-------+ | Handler_read_rnd_next | 13012 | +-----------------------+-------+ 1 row in set (0.08 sec) That's a HUGE performance difference. So yes, using LIKE when you can is useful. WHERE gives you a lot more POWER than LIKE, but it comes at a cost. Thanx! This is very important information, so I’ll show some examples:

mysql> show global status like ‘Handler_read_rnd_next’;
+———————–+——-+
| Variable_name | Value |
+———————–+——-+
| Handler_read_rnd_next | 13010 |
+———————–+——-+
1 row in set (0.00 sec)

mysql> show global status where Variable_name=’Handler_read_rnd_next’;
+———————–+——-+
| Variable_name | Value |
+———————–+——-+
| Handler_read_rnd_next | 13012 |
+———————–+——-+
1 row in set (0.08 sec)

That’s a HUGE performance difference. So yes, using LIKE when you can is useful. WHERE gives you a lot more POWER than LIKE, but it comes at a cost.

]]> By: ryan http://www.pythian.com/news/1222/show-status-where/#comment-276513 ryan Sat, 13 Sep 2008 15:54:27 +0000 http://www.pythian.com/blogs/1222/show-status-where#comment-276513 For the SHOW command, LIKE seems to be more efficient with the handler than WHERE. Compare the incremental output of: show global status like 'Handler_read_rnd_next'; show global status where Variable_name='Handler_read_rnd_next'; You can see by the output there that WHERE seems to act more like HAVING. Unlikely to matter when just ad-hoc investigating something, but might make a minor impact if you script something to run every second. For the SHOW command, LIKE seems to be more efficient with the handler than WHERE.

Compare the incremental output of:
show global status like ‘Handler_read_rnd_next’;
show global status where Variable_name=’Handler_read_rnd_next’;

You can see by the output there that WHERE seems to act more like HAVING. Unlikely to matter when just ad-hoc investigating something, but might make a minor impact if you script something to run every second.

]]>