Re: profiling question

[Chad MILLER]

On 12 Aug 2007, at 12:26, Vangelis Katsikaros wrote:
> In http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html
> "profiling" and "profiling_history_size" variables are noted as  
> session variables, which is also mentioned in
> http://dev.mysql.com/doc/refman/5.0/en/show-profiles.html
>
> However profiling_history_size can be set from the my.cnf file  
> where as
> profiling can't. Also from mysql command line it is possible to do ie
> SET GLOBAL profiling_history_size=10;
>
> So is profiling_history_size session but handled like global or simply
> hasn't been updated in the docs?

The session's history-size is set from the global size when the  
session is created.  You may think of it as a default value.

> Also I would like to ask if there is a reason for not having  
> profiling as global variable.

Yes, it's intentional.

Profiling is expensive, and it should never be left on.  This is a  
safeguard against our users who don't read the manual.

Furthermore, profiling data is session-specific.  Outside of a  
session, there's no way to access the profiling data.  Thus, it  
doesn't make sense to enable profiling from outside, when one can't  
access it from outside.

Now, it would be nice to create a way to write "remote" profiling  
data to a table.  Say, I'm in connection 23 and I want profiling data  
on connection 42 (or some expression that describes the session), it  
would be nice to turn on profiling and write its results to a  
particular table that I name.  I invite that feature to be implemented.

- chad

--
Chad Miller, Software Developer                         chad@stripped
MySQL Inc., www.mysql.com
Orlando, Florida, USA                                13-20z,  UTC-0400
Office: [phone]                         sip:6740@stripped



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