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Re: VARCHAR vs. TEXT - some performance numbers
Posted by: Rick James ()
Date: June 16, 2009 10:25PM

I thought I was forgetting something...

MyISAM puts TEXT and BLOB 'inline'. If you are searching a table (range scan / table scan), you are 'stepping over those cow paddies' -- costly for disk I/O. That is, the existence of the inline blob hurts performance in this case.

InnoDB puts only 767 bytes of a TEXT or BLOB inline, the rest goes into some other block. This is a compromise that sometimes helps, sometimes hurts performance.

Something else (Maria? Falcon? InnoDB plugin?) puts TEXTs and BLOBs entirely elsewhere. This would make a noticeable difference in performance when compared to VARCHAR. Sometimes TEXT would be faster (eg, range scan that does not need the blob); sometimes the VARCHAR would be faster (eg, if you need to look at it and/or return it).

Note: in later versions, VARCHAR can go up to 65535, making it nearly the same as TEXT, not just TINYTEXT.

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Subject Views Written By Posted
VARCHAR vs. TEXT - some performance numbers 199242 Rob Blick 07/31/2006 06:57AM
Re: VARCHAR vs. TEXT - some performance numbers 57285 Peter Zaitsev 07/31/2006 07:51AM
Re: VARCHAR vs. TEXT - some performance numbers 33711 Rob Blick 07/31/2006 09:48AM
Re: VARCHAR vs. TEXT - some performance numbers 24853 Regis Patuto 06/16/2009 01:12PM
Re: VARCHAR vs. TEXT - some performance numbers 26593 Rick James 06/16/2009 10:17PM
Re: VARCHAR vs. TEXT - some performance numbers 23281 Rick James 06/16/2009 10:25PM


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