Re: Postgres-R: primary key patches

From: Markus Wanner <markus(at)bluegap(dot)ch>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>, David Fetter <david(at)fetter(dot)org>, chris <cbbrowne(at)ca(dot)afilias(dot)info>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Postgres-R: primary key patches
Date: 2008-07-18 17:12:42
Message-ID: 4880CF0A.4010709@bluegap.ch
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Hi,

Alvaro Herrera wrote:
> I think the point here is that you need to distinguish which tuple you
> need to update. For this, our Replicator uses the primary key only;
> there's no way to use another candidate key (unique not null). It would
> certainly be possible to use a different candidate key,

Yeah, and for this to work, the *sender* needs to decide on a key to use.

> but as far as I
> know no customer has ever requested this.

I can't see the use case for a separate REPLICATION KEY, different from
the PRIMARY KEY, either..

> (FWIW we don't send the old values -- only the original PK columns, the
> values of columns that changed, and the "update mask" in terms of
> heap_modify_tuple.)

Yup, that's pretty much the same what I'm doing for Postgres-R.

Regards

Markus

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