Aggregate functions

marek_mar · 01-18-2005, 07:43 PM

Are aggregate functions fast when used with large sets of rows?

raf · 01-18-2005, 11:05 PM

depends ...
some agregationfunctions (like count()) are optimised to return very fast. if the columns you aply an agregationfunction on, are indexed, then functions like min() and max() will also be real fast.
but you usually use agregationfunctios because they are the most efficient way to agregate the data and have MySQL do the filtering and computing, so that you only need to return a very small recordset.
Using agregationfunctions will allways be more efficient then returning large recordsets, and then do the filtering and computations in your aplicationlayer (PHP or whatever).

marek_mar · 01-19-2005, 08:57 PM

Thank you raf!

raf · 01-19-2005, 09:09 PM

you're welcome

Hope you'll enjoy using them!

marek_mar · 01-19-2005, 09:48 PM

NMow I figured it is the only sane way to do it. Indexing reduced the execution time of my test query from +0.03 to 0.003!

01-18-2005, 07:43 PM	PM User \| #1
marek_mar Sensei Join Date: Aug 2003 Location: One step ahead of you. Posts: 2,815 Thanks: 0 Thanked 3 Times in 3 Posts	Aggregate functions Are aggregate functions fast when used with large sets of rows?

01-18-2005, 11:05 PM	PM User \| #2
raf Master Coder Join Date: Jul 2002 Posts: 6,589 Thanks: 0 Thanked 0 Times in 0 Posts	depends ... some agregationfunctions (like count()) are optimised to return very fast. if the columns you aply an agregationfunction on, are indexed, then functions like min() and max() will also be real fast. but you usually use agregationfunctios because they are the most efficient way to agregate the data and have MySQL do the filtering and computing, so that you only need to return a very small recordset. Using agregationfunctions will allways be more efficient then returning large recordsets, and then do the filtering and computations in your aplicationlayer (PHP or whatever). __________________ Posting guidelines I use to see if I will spend time to answer your question : http://www.catb.org/~esr/faqs/smart-questions.html

01-19-2005, 09:09 PM	PM User \| #4
raf Master Coder Join Date: Jul 2002 Posts: 6,589 Thanks: 0 Thanked 0 Times in 0 Posts	you're welcome Hope you'll enjoy using them! __________________ Posting guidelines I use to see if I will spend time to answer your question : http://www.catb.org/~esr/faqs/smart-questions.html

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01-19-2005, 08:57 PM	PM User \| #3
marek_mar Sensei Join Date: Aug 2003 Location: One step ahead of you. Posts: 2,815 Thanks: 0 Thanked 3 Times in 3 Posts	Thank you raf!

01-19-2005, 09:48 PM	PM User \| #5
marek_mar Sensei Join Date: Aug 2003 Location: One step ahead of you. Posts: 2,815 Thanks: 0 Thanked 3 Times in 3 Posts	NMow I figured it is the only sane way to do it. Indexing reduced the execution time of my test query from +0.03 to 0.003!