From: Tom Lane <tgl@sss.pgh.pa.us>
To: vik@postgresfriends.org
cc: pgsql-bugs@lists.postgresql.org,
        Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Subject: Re: BUG #17723: cache lookup failed for type 0
In-reply-to: <17723-2c4985ff111e7bba@postgresql.org>
References: <17723-2c4985ff111e7bba@postgresql.org>
Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
	message dated "Fri, 16 Dec 2022 15:38:04 +0000"
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Date: Fri, 16 Dec 2022 12:10:56 -0500
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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.

			regards, tom lane