Message-ID: <4FFE8E70.3060109@gmx.net>
Date: Thu, 12 Jul 2012 10:44:32 +0200
From: Andreas <maps.on@gmx.net>
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To: pgsql-sql@postgresql.org
CC: Kretschmer Andreas <akretschmer@spamfence.net>, M.Mamin@intershop.de
Subject: Re: Prevent double entries ... no simple unique index
References: <4FFD3050.3010509@gmx.net> <20120711081607.GA17798@tux>
	<20120711082458.GA19013@tux>
	<C4DAC901169B624F933534A26ED7DF310861B61A@JENMAIL01.ad.intershop.net>
	<20120712051445.GA5421@tux>
In-Reply-To: <20120712051445.GA5421@tux>
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Am 12.07.2012 07:14, schrieb Andreas Kretschmer:
> Marc Mamin <M.Mamin@intershop.de> wrote:
>
>> A partial index would do the same, but requires less space:
>>
>> create unique index on log(state) WHERE state IN (0,1);
>


OK, nice   :)

What if I have those states in a 3rd table?
So I can see a state-history of when a state got set by whom.


objects ( id serial PK, ... )
events ( id serial PK,  object_id integer FK on objects.id, ... )

event_states ( id serial PK,  event_id integer FK on events.id, state  
integer )

There still should only be one event per object that has state 0 or 1.
Though here I don't have the object-id within the event_states-table.

Is it still possible to have a unique index that needs to span over a 
join of events and event_states?