On 4 May 2011, at 23:57, Michał Piotrowski wrote: > 2011/5/4 Marco Pivetta <ocram...@gmail.com>: >> SQL is way faster than PHP processing. I would really go for a filtered >> join. That's what SQL is there for :) >> Just be sure to filter by index and to return a limited resultset. >> >> Sequential scan in PHP has to be ABSOLUTELY avoided :) > > I'm not sure how to do this if I need a multiple dynamically added conditions.
SQL (certainly in mySQL) supports conditionals in queries, so if the data you use to make the choice is in the database, you can do it all in the query. Another way to approach your problem is to have your web app trigger events when certain actions occur - this way you're approaching issues like "have already been purchased by at least one of his friends" from the other end. When someone buys a product, add it to each friend's recommendation list. Then your look-up query is much more simple. You can even queue these events up and process them later, since it's usually not vital that such information is "live". As an aside: typically very complex queries like this are done by background processes only periodically (e.g. every few hours) and stored in look-up tables or similar. Particularly as you start getting many users, complex queries quickly become a bottleneck, so you produce them offline beforehand and store them in a way that's simple and quick to fetch by your site's PHP scripts (in a simple cache table or object store). You never want a simple request page to be doing so much heavy lifting that it'll slow down and prevent you scaling later. If the heavy processing stuff is split off into a separate process, you can also move that process to another server later. -- Matt -- If you want to report a vulnerability issue on symfony, please send it to security at symfony-project.com You received this message because you are subscribed to the Google Groups "symfony users" group. To post to this group, send email to symfony-users@googlegroups.com To unsubscribe from this group, send email to symfony-users+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/symfony-users?hl=en
