Re: Speed differences between joins and subqueries?
On 04.06.2004 20:46 (+0200), Sasha Pachev wrote: Subquery optimizer is still is a very early stage in 4.1. Much more often than not, a carefully crafted join, union, or a sequence of queries using a temporary table will be faster. In fact, I wonder if it is even possible to write a machine subquery optimizer that will outperform a good human "optimizer" that re-writes them into something better digestible. Kind of like no super-smart JIT will ever beat a good C programmer on execution speed, although it might help with the development time. Could there be a program that I can present my query and it gives me some alternatives with a benchmark of them? This may help me to create optimized queries and may inspire me to optimize them even further into a direction I didn't think of yet... -- Yves Goergen <[EMAIL PROTECTED]> BlackBoard Internet Newsboard System --> blackboard.unclassified.de Free (GPL), easy to use and install, secure, innovative! (PHP+MySQL) -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/[EMAIL PROTECTED]
Re: Speed differences between joins and subqueries?
Daniel Ek wrote: Hi all, I am wondering if anyone have any knowledge if there is speed difference between joins (inner | outer | left | right) and subqueries. Would I actually gain preformance using subqueries (new since 4.1) against using the "old" joins? Would be interesting to hear comments on this matter, and also a detailed explanation on which is to prefer and why. Subquery optimizer is still is a very early stage in 4.1. Much more often than not, a carefully crafted join, union, or a sequence of queries using a temporary table will be faster. In fact, I wonder if it is even possible to write a machine subquery optimizer that will outperform a good human "optimizer" that re-writes them into something better digestible. Kind of like no super-smart JIT will ever beat a good C programmer on execution speed, although it might help with the development time. -- Sasha Pachev Create online surveys at http://www.surveyz.com/ -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/[EMAIL PROTECTED]
Speed differences between joins and subqueries?
Hi all, I am wondering if anyone have any knowledge if there is speed difference between joins (inner | outer | left | right) and subqueries. Would I actually gain preformance using subqueries (new since 4.1) against using the "old" joins? Would be interesting to hear comments on this matter, and also a detailed explanation on which is to prefer and why. Cheers Daniel -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/[EMAIL PROTECTED]
