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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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Re: VARCHAR vs. TEXT - some performance numbers
June 16, 2009 10:25PM

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