MySQL Performance: MySQL => Surprising: Where a quote usage dramatically slows down a request

Surprising: Where a quote usage dramatically slows down a request [message #1733]

Tue, 04 September 2007 08:33

sdeluca
Messages: 4
Registered: September 2007
Location: France

Junior Member

Hi there,

I wanted to subtmit a weird finding while optimizing our backend access (MySql 5.0.32-Debian_7etch1-log).

I have a table with the primary indexed column user_id (mediumint ( 8 )).

With the following code, we update some user's infos:

UPDATE phpbb_users SET flastcellupload = '1188382472' , fidcell='10459' WHERE user_id = '10915207';
Query OK, 0 rows affected (3.38 sec)
Rows matched: 0  Changed: 0  Warnings: 0

Note that user_id 10915207 does not exists (and card(user_id)=670+K).

This request takes 3+s to be executed.

And what if I remove the quote around the number, as follows?:

UPDATE phpbb_users SET flastcellupload = '1188382472' , fidcell='10459' WHERE user_id = 10915207;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 0  Changed: 0  Warnings: 0

As you can see, it takes almost nothing to perform.

I ran some similar tests on SELECT and I can say it has no effect (very quick in both syntaxex).

Any toughts?

Thanks in advance,
Sdl

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