[Tickets #12476] Re: Database running mad after update to 5.1.1

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Ticket URL: http://bugs.horde.org/ticket/12476
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  Ticket             | 12476
  Updated By         | Michael Rubinsky <mrubinsk at horde.org>
  Summary            | Database running mad after update to 5.1.1
  Queue              | Horde Framework Packages
  Version            | Git master
  Type               | Bug
  State              | Assigned
  Priority           | 2. Medium
  Milestone          |
  Patch              |
  Owners             | Michael Rubinsky
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Michael Rubinsky <mrubinsk at horde.org> (2013-07-24 03:40) wrote:

I think what's happening with the MAX query is that the index is in  
ASC order and the order of the columns in the composite index is in  
the wrong order. Creating the composite index on object_uid,  
history_modseq (instead of history_modseq, object_uid) reduces the  
number of rows to scan for me by multiple orders of magnitude.

ORDER BY/LIMIT query also seems to greatly improve performance as  
shown by EXPLAIN on my production server.  My development server uses  
the less efficient filesort but I'm thinking that's because the number  
of rows is much smaller.