[mythtv-users] Slow MySQL query after delete

Wade Maxfield mythtv at hotblack.co.nz
Fri Sep 7 01:36:36 UTC 2007

>On Sep 6, 2007, at 2:36 PM, f-myth-users at media.mit.edu wrote:
>>  Oh, whoops.  Hadn't considered that.  (Does Myth have a "suggested" or
>>  (gulp) "supported" set of storage engines, or is it claimed that any
>>  storage engine MySQL supports will "work"?  I'm assuming 99% of
>>  everybody leaves theirs at the default, but of course we don't know.)
>I'm actually curious if there are any performance benefits to using 
>one over the other.  My understanding is InnoDB's main benefit over 
>MyISAM is transaction support, which MythTV doesn't use, so I'm
>guessing no.  There may be other factors I'm not thinking of, though.

One major difference between them is MyISAM uses table level locking 
for updates, while InnoDB uses row level locking.  For a system that 
does multiple concurrent reads and writes, this could impact things.

And just to throw another variable out there (well 2 actually), there 
is a mysql-tuning script I came across a long time ago, and 2 of it's 
suggestions for ways to tweak performance with table locking issues 
are (direct quote from the script, typos included):

"If you have long running SELECT's against MyISAM tables and perform
frequent updates consider setting 'low_priority_updates=1'
If you have a high concurrentcy of inserts on Dynamic row-length tables
consider setting 'concurrent_insert=2'."

Maybe one of those suggestions could help...

  - Wade

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