Re: Expression errors with "FOR UPDATE" and postgres_fdw withpartition wise join enabled. - Mailing list pgsql-hackers

From Ashutosh Bapat
Subject Re: Expression errors with "FOR UPDATE" and postgres_fdw withpartition wise join enabled.
Date
Msg-id CAFjFpRdN=g_N+8mwuKujj2GsaAPS22aCQab0H4x2bSt9cvojjw@mail.gmail.com
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In response to Re: Expression errors with "FOR UPDATE" and postgres_fdw with partitionwise join enabled.  (Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>)
List pgsql-hackers
On Wed, Feb 14, 2018 at 2:50 PM, Etsuro Fujita
<fujita.etsuro@lab.ntt.co.jp> wrote:
>
> I'd vote for #1, but ISTM that that's more like a feature, not a fix.
> Pushing down ConvertRowtypeExprs to the remote seems to me to be the same
> problem as pushing down PHVs to the remote, which is definitely a feature
> development.  I think a fix for this would be to just give up pushing down a
> child join in foreign_join_ok or somewhere else if the reltarget of the
> child-join relation contains any ConvertRowtypeExprs.

That means we won't be able to push down any scans under a DML on a
partitioned table. That will be too restrictive.

I think the case of PHV and ConvertRowtypeExprs are different. The the
former we need a subquery to push PHVs, whereas to deparse
ConvertRowtypeExpr on the nullable side we can use the same strategy
as whole-row expression deparsing.

-- 
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company


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