Re: logical changeset generation v3 - comparison to Postgres-R change set format

From: Hannu Krosing <hannu(at)2ndQuadrant(dot)com>
To: Markus Wanner <markus(at)bluegap(dot)ch>
Cc: Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: logical changeset generation v3 - comparison to Postgres-R change set format
Date: 2012-11-17 14:57:39
Message-ID: 50A7A5E3.3050608@2ndQuadrant.com
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On 11/17/2012 03:00 PM, Markus Wanner wrote:
> On 11/17/2012 02:30 PM, Hannu Krosing wrote:
>> Is it possible to replicate UPDATEs and DELETEs without a primary key in
>> PostgreSQL-R
> No. There must be some way to logically identify the tuple. Note,
> though, that theoretically any (unconditional) unique key would suffice.
> In practice, that usually doesn't matter, as you rarely have one or more
> unique keys without a primary.
...
> Are there other reasons to want tables without primary keys that I'm
> missing?
>
Nope. The only place a table without a primary key would be needed is a
log table, but as these are (supposed to be) INSERT-only this is not a
problem for them.

Hannu

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