Re: WITH NOT MATERIALIZED and DML CTEs

From: Elvis Pranskevichus <elprans(at)gmail(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: WITH NOT MATERIALIZED and DML CTEs
Date: 2019-06-03 15:56:43
Message-ID: 1862252.d4nv1szfvR@hammer.magicstack.net
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On Monday, June 3, 2019 11:50:15 A.M. EDT Andres Freund wrote:
> > This seems like an omission to me. Ideally, the presence of an
> > explicit "NOT MATERIALIZED" clause on a data-modifying CTE should
> > disable the "run to completion" logic.
>
> I don't see us ever doing that. The result of minor costing and other
> planner changes would yield different updated data. That'll just
> create endless bug reports.

I understand why the rule exists in the first place, but I think that an
explicit opt-in signals the assumption of responsibility and opens the
possibility of using this in a well-defined evaluation context, such as
CASE WHEN.

Elvis

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