Re: [PATCH] Resolve unknown-type literals in GRAPH_TABLE COLUMNS

From: Peter Eisentraut <peter(at)eisentraut(dot)org>
To: Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, SATYANARAYANA NARLAPURAM <satyanarlapuram(at)gmail(dot)com>
Cc: Junwang Zhao <zhjwpku(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: [PATCH] Resolve unknown-type literals in GRAPH_TABLE COLUMNS
Date: 2026-05-04 15:12:02
Message-ID: 2b3490b5-e0e5-4f3b-9165-df1990bee70b@eisentraut.org
Views: Whole Thread | Raw Message | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

On 29.04.26 16:09, Ashutosh Bapat wrote:
> On Mon, Apr 27, 2026 at 11:34 AM SATYANARAYANA NARLAPURAM
> <satyanarlapuram(at)gmail(dot)com> wrote:
>>
>> Hi,
>>
>> On Sun, Apr 26, 2026 at 8:10 AM Junwang Zhao <zhjwpku(at)gmail(dot)com> wrote:
>>>
>>> Hi SATYANARAYANA,
>>>
>>> On Sun, Apr 26, 2026 at 3:53 AM SATYANARAYANA NARLAPURAM
>>> <satyanarlapuram(at)gmail(dot)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patch 5/5, so maybe you had some unpublished local changes?).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.

In response to

Browse pgsql-hackers by date

  From Date Subject
Next Message Lukas Fittl 2026-05-04 15:22:26 Re: EXPLAIN: showing ReadStream / prefetch stats
Previous Message Peter Eisentraut 2026-05-04 14:47:51 Re: [Bug][patch]: After dropping the last label from a property graph element, invoking pg_get_propgraphdef() triggers an assertion failure