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[Thierry Carrez <thierry.carrez+lp@xxxxxxxxx>]

** Changed in: cinder
       Status: Fix Committed => Fix Released

** Changed in: cinder
    Milestone: None => juno-3

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https://bugs.launchpad.net/bugs/1348720

Title:
  Missing index for expire_reservations

Status in Cinder:
  Fix Released
Status in OpenStack Compute (Nova):
  Fix Committed

Bug description:
  While investigating some database performance problems, we discovered
  that there is no index on deleted for the reservations table. When
  this table gets large, the expire_reservations code will do a full
  table scan and take multiple seconds to complete. Because the expire
  runs on a periodic, it can slow down the master database significantly
  and cause nova or cinder to become extremely slow.

  > EXPLAIN UPDATE reservations SET updated_at=updated_at, deleted_at='2014-07-24 22:26:17', deleted=id WHERE reservations.deleted = 0 AND reservations.expire < '2014-07-24 22:26:11';
  +----+-------------+--------------+-------+---------------+---------+---------+------+--------+------------------------------+
  | id | select_type | table        | type  | possible_keys | key    | key_len | ref  | rows  | Extra                        |
  +----+-------------+--------------+-------+---------------+---------+---------+------+--------+------------------------------+
  |  1 | SIMPLE      | reservations | index | NULL          | PRIMARY | 4      | NULL | 950366 | Using where; Using temporary |
  +----+-------------+--------------+-------+---------------+---------+---------+------+--------+------------------------------+

  An index on (deleted, expire) would be the most efficient.

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