[mythtv-commits] Ticket #10023: Improve performance of time search

MythTV noreply at mythtv.org
Wed Sep 7 11:35:45 UTC 2011


#10023: Improve performance of time search
-------------------------------------+-------------------------------------
 Reporter:  dekarl@…                 |           Type:  Bug Report -
   Status:  new                      |  General
Milestone:  unknown                  |       Priority:  minor
  Version:  Trunk Head               |      Component:  MythTV - General
 Keywords:                           |       Severity:  medium
                                     |  Ticket locked:  0
-------------------------------------+-------------------------------------
 The SQL query for time search takes 2 minutes over here. By slightly
 refactoring the query that can be brought down to 2 seconds. Just factor
 out the description column into a superquery with the actual query being a
 subquery.

 The new query looks like:
 {{{
 select program.description, sub.* from program, (
 SELECT DISTINCT program.chanid,
 ... here is the old query but without the description column ...
 ) as sub where program.chanid=sub.chanid and
 program.starttime=sub.starttime;
 }}}

 The reason for the difference is each description taking 48kb of memory no
 matter how much of that is actually used leading to the whole joining and
 sorting being done on the hard disk because it doesn't fit into the memory
 buffer. (at least that's what I suspect)

-- 
Ticket URL: <http://code.mythtv.org/trac/ticket/10023>
MythTV <http://code.mythtv.org/trac>
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