Postgres Pro
Downloads
Home   >   mailing lists

Re: SEARCH and CYCLE clauses - Mailing list pgsql-hackers

From Pavel Stehule
Subject Re: SEARCH and CYCLE clauses
Date
Msg-id CAFj8pRDP8=X6gFz0OUOjAigxAY2L+rekDD0f+jeBGB8C_X9eDQ@mail.gmail.com
Whole thread Raw
In response to Re: SEARCH and CYCLE clauses  (Peter Eisentraut <peter.eisentraut@2ndquadrant.com>)
Responses Re: SEARCH and CYCLE clauses
List pgsql-hackers
Tree view


pá 9. 10. 2020 v 11:40 odesílatel Peter Eisentraut <peter.eisentraut@2ndquadrant.com> napsal:
On 2020-09-22 20:29, Pavel Stehule wrote:
> The result is correct. When I tried to use UNION instead UNION ALL, the
> pg crash

I fixed the crash, but UNION [DISTINCT] won't actually work here because
row/record types are not hashable.  I'm leaving the partial support in,
but I'm documenting it as currently not supported.
 
 I think so UNION is a common solution against the cycles. So missing support for this specific case is not a nice thing. How much work is needed for hashing rows. It should not be too much code.


> looks so clause USING in cycle detection is unsupported for DB2 and
> Oracle - the examples from these databases doesn't work on PG without
> modifications

Yeah, the path clause is actually not necessary from a user's
perspective, but it's required for internal bookkeeping.  We could
perhaps come up with a mechanism to make it invisible coming out of the
CTE (maybe give the CTE a target list internally), but that seems like a
separate project.

The attached patch fixes the issues you have reported (also the view
issue from the other email).  I have also moved the whole rewrite
support to a new file to not blow up rewriteHandler.c so much.

--
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

pgsql-hackers by date:

Previous
From: Noah Misch
Date:
Subject: Re: powerpc pg_atomic_compare_exchange_u32_impl: error: comparison of integer expressions of different signedness (Re: pgsql: For all ppc compilers, implement compare_exchange and) fetch_add
Next
From: Greg Nancarrow
Date:
Subject: Re: Parallel INSERT (INTO ... SELECT ...)