Re: INSERT OU UPDATE WITHOUT SELECT? - Mailing list pgsql-performance

From D'Arcy J.M. Cain
Subject Re: INSERT OU UPDATE WITHOUT SELECT?
Date
Msg-id 20060530190508.aa47bafe.darcy@druid.net
Whole thread Raw
In response to Re: INSERT OU UPDATE WITHOUT SELECT?  ("Dave Dutcher" <dave@tridecap.com>)
Responses Re: INSERT OU UPDATE WITHOUT SELECT?  ("Jim C. Nasby" <jnasby@pervasive.com>)
List pgsql-performance
On Tue, 30 May 2006 17:54:00 -0500
"Dave Dutcher" <dave@tridecap.com> wrote:
> What I do when I'm feeling lazy is execute a delete statement and then
> an insert.  I only do it when I'm inserting/updating a very small number
> of rows, so I've never worried if its optimal for performance.  Besides
> I've heard that an update in postgres is similar in performance to a
> delete/insert.

Well, they are basically the same operation in PostgreSQL.  An update
adds a row to the end and marks the old one dead.  A delete/insert
marks the row dead and adds one at the end.  There may be some
optimization if the engine does both in one operation.

--
D'Arcy J.M. Cain <darcy@druid.net>         |  Democracy is three wolves
http://www.druid.net/darcy/                |  and a sheep voting on
+1 416 425 1212     (DoD#0082)    (eNTP)   |  what's for dinner.

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