Rails Ruby on Rails

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  James February 4th, 2011 @ 05:22 PM

  Turns out it has nothing to do with the joins.

  Animal.limit(1).count
  => 1297

  Is that expected behavior?

  Found this by trying to do (essentially) Animal.limit(1).update_all(...) -- not surprisingly based on the above, it's updating every record.

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  Jan Xie February 5th, 2011 @ 01:04 PM

  Model.limit(1).count generate correct sql (select count(*) from model limit 1), it's mysql's behavior:

  mysql> select count(*) from knowledges limit 1;
  +----------+
  | count(*) |
  +----------+
  |      842 |
  +----------+
  1 row in set (0.00 sec)
  

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  James February 5th, 2011 @ 03:55 PM

  Yeah -- that makes perfect sense -- forgot that count and size actually modify the query and return a single row.

  So what about my specific case with update_all? It builds the update_all query including the "wheres" and discards the limit:
  Animal.limit(1).joins(:lot).where("animals.location_id" => 20).where("lots.species" => "Horse").update_all(:location_id => 20)

  AREL (2.7ms) UPDATE animals INNER JOIN lots ON lots.id = animals.lot_id SET location_id = 20 WHERE animals.location_id = 20 AND lots.species = 'Horse'

• 

  Aaron Patterson February 25th, 2011 @ 08:02 PM

  • State changed from “new” to “invalid”
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  James,

  order must also be supplied if you want the limit to work on updates.