From: Michael Artz <mlartz@gmail.com>
To: Jim C. Nasby <jnasby@pervasive.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Bulk loading/merging
Date: Thu, 1 Jun 2006 14:04:46 -0400
Message-ID: <e9c163070606011104w1d0cf7a6jca8cf5b36f2d8de3@mail.gmail.com> (raw)
In-Reply-To: <20060531010922.GC59464@pervasive.com>
References: <ce4072df0605261148g4ec22267gc54b6b445e47c855@mail.gmail.com>
<20060531010922.GC59464@pervasive.com>
On 5/30/06, Jim C. Nasby <jnasby@pervasive.com> wrote:
> Your best bet is to do this as a single, bulk operation if possible.
> That way you can simply do an UPDATE ... WHERE EXISTS followed by an
> INSERT ... SELECT ... WHERE NOT EXISTS.
hmm, I don't quite understand what you are saying and I think my
basic misunderstanding is how to use the UPDATE ... WHERE EXISTS to merge
data in bulk. Assuming that I bulk COPYed the data into a temporary
table, I'd need to issue an UPDATE for each row in the newly created table,
right?
For example, for a slightly different key,count schema:
CREATE TABLE kc (key integer, count integer);
and wanting to merge the following data by just updating the count for a
given key to the equivalent of OLD.count + NEW.count:
1,10
2,15
3,45
1,30
How would I go about using UPDATE ... WHERE EXISTS to update the "master" kc
table from a (temporary) table loaded with the above data?
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To: pgsql-performance@postgresql.org
Cc: mlartz@gmail.com, jnasby@pervasive.com
Subject: Re: Bulk loading/merging
In-Reply-To: <e9c163070606011104w1d0cf7a6jca8cf5b36f2d8de3@mail.gmail.com>
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