Message-ID: <80f95342-cc09-4236-a2d7-68538fbfc41b@wikimedia.org>
Date: Mon, 28 Apr 2025 21:22:56 +1000
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Subject: Re: Upsert error "column reference is ambiguous"
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To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-general@lists.postgresql.org
References: <a31a76b6-b176-47fe-8778-9dfece231341@wikimedia.org>
 <697017.1745837694@sss.pgh.pa.us>
From: Tim Starling <tstarling@wikimedia.org>
In-Reply-To: <697017.1745837694@sss.pgh.pa.us>
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On 28/4/25 20:54, Tom Lane wrote:
> Even if I were on board with arbitrarily adopting one of the two
> possible interpretations, it's far from obvious to me that most people
> would agree that "v" should mean the value from the existing row,
> rather than the new value.  Better to make them say which they want.

OK sure, no way to tell, but if every other DBMS does it the same way 
then that might be a hint.

Also, I'm just saying, the upsert feature is fully useless to me with 
this name resolution policy.

In the single-row case, there's no need for EXCLUDED at all, because 
the client knows everything about the excluded row. Recall my example:

INSERT INTO t VALUES (1,1) ON CONFLICT (k) DO UPDATE SET v=v+1;

If I meant SET v=EXCLUDED.v+1 I would have just written v=2. The 
default policy (in other DBMSes) follows by analogy from the 
single-row case.

-- Tim Starling