preventing multiple simultaneous queries with php/mysql live search

Question

I have a working live search system that on the whole works very well. However it often runs into the problem that many versions of the search query on the server are running simultaneously, if users are typing faster than the results can be returned.

I am aborting the ajax request on receoipt of a new one, but that of course does not affect the query already in process on the server, and you end up with a severe bottleneck and a long wait to get your final results. I am using MySQL with MyISAM tables for this, and there does not seem to be any advantage in converting to InnoDB as the result sets will be the sane rows.

I tried using a session variable to make php wait if this session already has a query in progress but that seems to stop it working altogether.

The problem is solved if I make the ajax requests syncrhonous, but that would rather defeat the object here.

I was wondering if anyone had any suggestions as to how to make this work properly.

Best regards John

Answer 1

Before doing anything more complicated, have you considered not sending the request until the user has stopped typing for at least a certain time interval (say, 1 second)? That should dramatically cut the number of requests being made with little effort on your part.