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Re: blob to mediumblob or largeblob
Posted by: Rick James
Date: July 20, 2011 10:09AM

You caught me! I had not noticed that.

The statement is scary. However, it does not really mean that the row cannot be bigger than 65KB; it means that the row won't be stored (and handled) in a contiguous chunk if it is 'too big'.

InnoDB (in earlier versions) spills VARCHAR, TEXT, BLOB after 767 bytes per column (or something like that).

MyISAM (based on your link) spills TEXT or BLOB after it gets too big. (Note: Apparently not VARCHAR(s).)

Back to your case -- Most of your rows have < 65KB in the BLOB, correct? So, only a few would need to spill. So, even with the extra overhead of linking to elsewhere, the performance hit is not worth worrying about.

How compressible is the data? You can get more of a performance boost by compressing the blob before handing it to MySQL. This is because you will be decreasing the disk activity, which is the biggest factor in performance. (Examples, English text compresses 3:1; jpeg, gif don't compress; bmp and Word compress a lot.)

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Re: blob to mediumblob or largeblob
July 20, 2011 10:09AM


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