[mythtv] Is it normal to rerun the same select query every 8 seconds?

[Göran Uddeborg]

I moved the database server to a different machine than where the
backend and default frontend is running.  That made me notice that the
mysqld daemon was actually using a noticeable amount of CPU time.
I enabled tracing, and saw that the vast majority of events sers
processing of select calls like this one:

Execute   SELECT chanid, useonairguide, channel.sourceid FROM channel, dtv_multiplex WHERE serviceid        = 5620   AND       networkid        = 8945   AND       transportid      = 1021 AND       channel.mplexid  = dtv_multiplex.mplexid

It is repeated over and over for different combinations of serviceid,
networkid and transportid.  I traced a little over an hour, and got a
total of almost 90000 such selections, or around 21 a second.
Checking a particular combination of values to select, I got around
one such particular query every 8 seconds.

When I run some of the selections manually, I get an empty set all the
time.  (I haven't tried all of them.)  Which makes me even more
suspicious of this.

Things do work.  The server is able to handle the work, and watching
TV works as expected.  But it appears a bit strange, and I got a bit
suspicious.  So I thought I could ask: is it really normal?  Does it
make sense for MythTV to repeat these questions over and over?  Or
could it be an indication of some bug that should be traced?  Either
in MythTV or in my configuration?