Re: Switching from MySQL: ON DUPLICATE KEY UPDATE, plpgsql function

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От Tguru
Тема Re: Switching from MySQL: ON DUPLICATE KEY UPDATE, plpgsql function
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Msg-id 24254206.post@talk.nabble.com
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Ответ на Re: Switching from MySQL: ON DUPLICATE KEY UPDATE, plpgsql function  (Justin <justin@emproshunts.com>)
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Justin-95 wrote:
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> APseudoUtopia wrote:
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>   thread, then logs out (intending to read all the other forum threads
> at some point in the future when they log in again). If I used a VIEW,
> it would automatically consider all those unread forum posts to be
> read when the user logs out.
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> That wouldn't work. What if a user logs in, reads only one forum
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> You are keeping a list of all the forums a user has read,  i would not
> worry about making sure the table tracking user activity has duplicate
> key values. The select can be limited to return just on row with the
> highest time stamp then compare this result to figure out what forms
> the user has not read yet.  This eliminates one of problems but creates
> a problem where table tracking user activity is going bloat but in low
> traffic times delete the duplicate values.
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> A similar topic was discussed  on the performance  mailing list, where
> updates are hung for several seconds for a similar tracking table...
> http://archives.postgresql.org/pgsql-performance/2009-06/msg00300.php
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