| From: | Emi Lu <emilu(at)encs(dot)concordia(dot)ca> |
|---|---|
| To: | "A(dot) Kretschmer" <andreas(dot)kretschmer(at)schollglas(dot)com> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: About updates |
| Date: | 2006-03-10 16:13:43 |
| Message-ID: | 4411A5B7.40500@encs.concordia.ca |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
Thanks Andreas. That was a quick response.
So way 1 must be quicker.
>am 10.03.2006, um 10:46:39 -0500 mailte Emi Lu folgendes:
>
>
>>Hello,
>>
>>postgresql 8.0.1, in a plpgsql function
>>
>>To update columns' values in a table (without OID), if I ran:
>>1. "update table1 set col1 = ..., col2 = ... ... col100 ="
>>
>>or
>>2.
>>"update table1 set col1 = "
>>...
>>"update table1 set col100 = "
>>
>>way 1 only has one disk I/O, right? While way 2 is more time consuming
>>since there is disk I/O when a update is ran.
>>
>>
>
>Because of MVCC every UPDATE is practical a DELETE + INSERT.
>Way1: you have only one DELETE+INSERT, Way2 one hundred, and you have
>100 dead rows until the next VACUUM.
>
>
>HTH, Andreas
>
>
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