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Re: PBXT issues


On May 6, 2010, at 1:25 PM, Alexandre Almeida wrote:


I was wondering. Can you say that PBXT works much better with fixed length rows?

PBXT works well with both fixed and variable length rows. But fix length records will not generally not require any tuning.



Em 06/05/2010, às 03:32, Paul McCullagh escreveu:

Hi Monty,

On May 5, 2010, at 7:02 PM, Michael Widenius wrote:

"Paul" == Paul McCullagh <paul.mccullagh@xxxxxxxxxxxxx> writes:


Paul> PBXT can help you out with this. Do the following:

Paul> (1) Load the telpbxt table with a few 1000 rows (or use telpbxt2,
Paul> since telpbxt already has too many rows in it).
Paul> (2) In mysql client enter: CHECK TABLE telpbxt2; (note: do not do this Paul> on a table with millions of rows. It will take very long to complete). Paul> (3) Check the MySQL error log, you should see something like the
Paul> output below.

Paul> CHECK TABLE: ./test/telpbxt
Paul> Record buffer size      = 1024
Paul> Fixed length rec. len.  = 1020
Paul> Handle data record size = 638
Paul> Min/max header size     = 14/26
Paul> Min/avg/max record size = 19/624/1019
Paul> Avg row len set for tab = not specified
Paul> Rows fixed length       = NO
Paul> Maximum fixed size      = 16384
Paul> ...

Paul> Paste the output in an e-mail, and I will show you what to use for the

Would it be hard for PBXT to as part of the CHECK TABLE add:

Optimial create AVG_ROW_LENGTH: ?

Currently CHECK TABLE prints:

Average comp. rec. len. = 200

This is the closest to your suggestion of an "Optimal create AVG_ROW_LENGTH", there is at the moment.

But, this value is not necessarily optimal.

Exactly what is optimal depends on a few additional factors, like whether you want to optimize for size or caching behavior.

What I can do is add more information to help in this decision making process, and output a "Recommended AVG_ROW_LENGTH".

Then I can change OPTIMIZE TABLE to automatically set this value, if no explicit AVG_ROW_LENGTH has been set yet.

Best regards,


Paul McCullagh
PrimeBase Technologies

Paul McCullagh
PrimeBase Technologies