Re: Optimising Time to Output Listings from a Search

[Harrison Fisk]

Hi,

The first (and most likely worst!) thing I see is:

result = mysql_query("$querystring;",$link);
$num_rows = mysql_num_rows($result);

and then doing it again with LIMIT.

Basically imagine you have 50,000 rows that match. In the first one you are retrieving 50000 rows, and then the first few again. That is extremely inefficient.

To get the number of matching rows you should either use the SQL_CALC_FOUND_ROWS functionality or use a COUNT(*) to find the number instead. That way you aren't retrieving a huge result set for no reason at all.

Of course many of your other ideas might increase performance as well, but I think this would be the most significant thing you could do.

Harrison Fisk, Trainer and Consultant
MySQL AB, www.mysql.com