[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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