Message-ID: <deb5b865-25de-b894-2d3d-44470eb86a88@postgresfriends.org>
Date: Fri, 16 Dec 2022 20:36:27 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.4.2
Subject: Re: BUG #17723: cache lookup failed for type 0
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-bugs@lists.postgresql.org,
 Peter Eisentraut <peter.eisentraut@enterprisedb.com>
References: <17723-2c4985ff111e7bba@postgresql.org>
 <3697954.1671210656@sss.pgh.pa.us>
From: Vik Fearing <vik@postgresfriends.org>
Content-Language: en-US
In-Reply-To: <3697954.1671210656@sss.pgh.pa.us>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Archived-At: 
 <https://www.postgresql.org/message-id/deb5b865-25de-b894-2d3d-44470eb86a88%40postgresfriends.org>
Precedence: bulk

On 12/16/22 18:10, Tom Lane wrote:
> PG Bug reporting form <noreply@postgresql.org> writes:
>> This query:
> 
>> WITH RECURSIVE
> 
>> run(x, y) AS (
>>    SELECT 0, 0
>>    UNION ALL
>>    SELECT x, y FROM run AS r WHERE r.is_cycle
>> )
>> CYCLE x, y SET is_cycle USING path
> 
>> TABLE run
>> ;
> 
>> in which I mistakenly tried to access the is_cycle column from inside the
>> wle, provokes the following error:
> 
>> ERROR:  XX000: cache lookup failed for type 0
>> LOCATION:  typeOrDomainTypeRelid, parse_type.c:699
> 
> Yeah.  We are calling addRangeTableEntryForCTE inside parse analysis of
> the CTE's query, and it's generating a ParseNamespaceItem with p_vartype = 0
> because analyzeCTE hasn't yet identified the cycle_mark_type.  That
> eventually results in a Var with vartype 0, confusing later parse analysis.
> 
> It looks to me like we can just move that part of the code up to before
> we recurse to parse_sub_analyze, though.  AFAICS, identification of the
> cycle column type needn't (and had better not) depend on any
> characteristics of the CTE's query.

Indeed, it should only depend on the TO and DEFAULT subclauses (not 
shown here).

Thanks for the fix!
-- 
Vik Fearing