[mythtv-users] Slow MySQL query after delete

[Larry K]

I am also having trouble with the BUSQ when I delete recordings, with query
times no better than 7-8 seconds.  This is on an Athlon 2500+ with 512MB
ram.  Myth 0.20 and MySQL 5.0.37, I think.   Before I upgraded to 0.20, I
was running 0.18 and this problem did not exist for me.  I'm guessing this
BUSQ was introduced after 0.18.

I cleaned up my recording schedules to eliminate duplicate schedules (there
were a few), and I also tried to avoid schedules on 'any channel'.  I
currently have 4,800 rows in oldrecorded, 550 rows in recordmatch, and 100
rows in record.  None of this seems excessive to me.  I also optimized my
database, and it still takes 6-7 seconds to run this query.

I wonder if 6-7 seconds is as good as it gets for me?   Have I hit the
wall?  Can anyone with a config similar to mine get this query to run in say
1 second?

/etc/my.conf:

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
key_buffer = 16M
table_cache = 128
sort_buffer_size = 2M
myisam_sort_buffer_size = 8M
query_cache_size = 16M
log_slow_queries=/var/log/slowsql.log
long_query_time=5

[mysql.server]
user=mysql
basedir=/var/lib

[safe_mysqld]
err-log=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid



On 11/24/07, crs23 <pvr at groundhog.pair.com> wrote:
>
>
> I used MythWeb to both discover duplicates by inspection and delete them.
> That took a long time because of the very problem I was trying to fix but
> each deletion went faster than the last as the query got faster and
> faster.
> A way to delete multiple recordings or recording rules at once would be
> nice
> but I wasn't about to try deleting records directly from the database
> because I don't know if that would cause some kind of inconsistency
> between
> tables.
>
>
> Larry K wrote:
> >
> > What was your method to determine the duplicates?  And did you simply
> > issue
> > a SQL delete to get rid of them, or some other mechanism?
> >
> > On 9/6/07, crs23 <pvr at groundhog.pair.com> wrote:
> >>
> >>
> >>
> >> Michael T. Dean wrote:
> >> >
> >> > I don't think much testing has been done on systems having identical
> >> > recording rules.  Though it shouldn't cause issues, cleaning out the
> >> > duplicates (triplicates?  whatever) would significantly simplify the
> >> > query's processing, so doing so would be very much to your advantage.
> >> >
> >>
> >> Done and the improvement was substantial.  There were several multiple
> >> entries.  One program had about a dozen duplicate entries and that just
> >> happened to be the program with the most previously recorded
> episodes.  I
> >> also changed the recordings to be on a particular channel instead of
> any
> >> channel which I think helped to.
> >>
> >> I'm now down to ~150,000 rows examined in 5.5 seconds, 696 rows
> >> returned.  5
> >> or 6 seconds is hugely better but still a bit of an annoyance.  But I'm
> >> very
> >> pleased with the results so far and the incredible support I've
> received
> >> on
> >> this forum.  Thank you to everyone!
> >>
> >> --
> >> View this message in context:
> >>
> http://www.nabble.com/Slow-MySQL-query-after-delete-tf4366877s15552.html#a12534738
> >> Sent from the mythtv-users mailing list archive at Nabble.com.
> >>
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> Sent from the mythtv-users mailing list archive at Nabble.com.
>
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