[mythtv] innodb vs myism preformance

[Ed Wildgoose]

>
> Thanks for the quick response.
>
> Ok, well I decided to switch the database back to test it, and it is 
> slow as hell again. This time I did:
>
> for a in $(ls *frm | cut -f1 -d. ); do echo "use mythconverg; ALTER 
> TABLE $a TYPE=MYISAM;"|mysql ; done


 From your symptoms and without looking at the code, my first thought 
was some kind of transaction wrapping in the myth delete function so 
that the metadata delete and disk delete would both be sure to happen.  
However, in retrospect I think that's a bit advanced for mysql.

So that suggests that the next most likely place to look is the recorded 
markup table.  If you have an mpeg2 recording then you have a huge bunch 
of rows stored in this table which have to be deleted.  Can you try just 
changing this single table and re-benching to see what happens?

If this is the case then you can at least grep the code and find the 
delete function and see if it's doing the delete in the obvious way, 
rather than one row at a time.  If there is nothing to optimise here 
then I guess we could look at whether the table is under/over indexed.  
Failing that I think switching that table to innodb sounds like the way 
ahead...

Curious to hear if you can track it down further to a single table

Ed W