Dear developers,

when reporting features are developed, please consider that software may be used on a site with millions of rows in tables. Please always check if indexes can be used for whole report, if not, please consider avoiding such feature, or consult people with access to database on #wikimedia-tech. If you actually have access to database, do not hesitate to EXPLAIN a query on our live datasets and evaluate costs of operation. Otherwise site goes down or crawls and both users and operators are frustrated ;-) Remember, less data query needs to read - faster it is!!!!!! :) And better for performance is when no data is read, of course ;-)

Thanks, Domas