Feedback-ID: ie0a040ee:Fastmail
Message-ID: <2b3490b5-e0e5-4f3b-9165-df1990bee70b@eisentraut.org>
Date: Mon, 4 May 2026 17:12:02 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH] Resolve unknown-type literals in GRAPH_TABLE COLUMNS
To: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>,
 SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>
Cc: Junwang Zhao <zhjwpku@gmail.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
References: 
 <CAHg+QDcyKNWyzDoKMxiZNjv7C-wAxs8y0ZoNkOV137Y+nk3UXg@mail.gmail.com>
 <CAEG8a3KTP1sX+RbPFNST4kHdeRZQR5-dd6kEihV56=K5irrhyQ@mail.gmail.com>
 <CAHg+QDdzUMW4qQmywiPmVo2z3+HccFZL+mujdXbB+ghU21u7dA@mail.gmail.com>
 <CAExHW5vmmAS6Vroh8W9+vmuM2ReocODRCWPqYozGSyhxCxxL+Q@mail.gmail.com>
Content-Language: en-US
From: Peter Eisentraut <peter@eisentraut.org>
In-Reply-To: 
 <CAExHW5vmmAS6Vroh8W9+vmuM2ReocODRCWPqYozGSyhxCxxL+Q@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Archived-At: 
 <https://www.postgresql.org/message-id/2b3490b5-e0e5-4f3b-9165-df1990bee70b%40eisentraut.org>
Precedence: bulk

On 29.04.26 16:09, Ashutosh Bapat wrote:
> On Mon, Apr 27, 2026 at 11:34 AM SATYANARAYANA NARLAPURAM
> <satyanarlapuram@gmail.com> wrote:
>>
>> Hi,
>>
>> On Sun, Apr 26, 2026 at 8:10 AM Junwang Zhao <zhjwpku@gmail.com> wrote:
>>>
>>> Hi SATYANARAYANA,
>>>
>>> On Sun, Apr 26, 2026 at 3:53 AM SATYANARAYANA NARLAPURAM
>>> <satyanarlapuram@gmail.com> wrote:
>>>>
>>>> Hi hackers,
>>>>
>>>> transformRangeGraphTable() calls transformExpr() and
>>>> assign_list_collations() for COLUMNS expressions but missed calling
>>>> resolveTargetListUnknowns(). As a result, literals such as 'val1'
>>>> in a COLUMNS clause retained type "unknown", causing failures with
>>>> ORDER BY, UNION, and output conversions.
>>>>
>>>> Fix by calling resolveTargetListUnknowns() on the columns target
>>>> list right after assign_list_collations(), similar to SELECT target lists in
>>>> transformSelectStmt().
>>>>
>>>> Attached a patch to fix this, which also includes test cases to reproduce.
>>>
>>> I can reproduce this and the patch fixes it.
>>>
>>> One question: why is resolveTargetListUnknowns called after
>>> assign_list_collations?
>>>
>>> I'm asking because in transformSelectStmt, resolveTargetListUnknowns
>>> is invoked before assign_query_collations. It might not matter, but keeping
>>> the order consistent would be good for readers.
>>
>>
>> Updated the patch. It should be before.
> 
> Do we really need a test for ORDER BY on a literal column? I replaced
> all the test queries with a single one which covers all the scenarios
> covered by those queries.
> 
> The patch needed to consider pstate->p_resolve_unknowns. Unknown
> literals are not resolved as text always. See the test query.

I couldn't find a commit to apply this patch cleanly (the subject says 
patch 5/5, so maybe you had some unpublished local changes?).  After 
applying the test case manually, it looks like the test output is 
already correct without the code change.  So if this patch is still 
required, we need a better test case.