2017-05-03 19:33 GMT+02:00 Alvaro Herrera <alvhe...@2ndquadrant.com>:

> David Fetter wrote:
> > When we add a "temporary" GUC, we're taking on a gigantic burden.
> > Either we support it forever somehow, or we put it on a deprecation
> > schedule immediately and expect to be answering questions about it for
> > years after it's been removed.
> >
> > -1 for the GUC.
> Absolutely.
> So ISTM we have three choices:
> 1) we switch unmarked CTEs as inlineable by default in pg11.  What seems
> likely to happen for a user that upgrades to pg11 is that 5 out of 10
> CTE-using queries are going to become faster than with pg10, and they
> are going to be happy; 4 out of five are going to see no difference, but
> they didn't have to do anything about it; and the remaining query is
> going to become slower, either indistinguishably so (in which case they
> don't care and they remain happy because of the other improvements) or
> notably so, in which case they can easily figure where to add the
> MATERIALIZED option and regain the original performance.
> 2) unmarked CTEs continue to be an optimization barrier, but we add
> "WITH INLINED" so that they're inlineable.  Some users may wonder about
> it and waste a lot of time trying to figure out which CTEs to add it to.
> They see a benefit in half the queries, which makes them happy, but they
> are angry that they had to waste all that time on the other queries.
> 3) We don't do anything, because we all agree that GUCs are not
> suitable.  No progress.  No anger, but nobody is happy either.

yes, these variants are all.

@2 is only little bit better than bad @3 - is not nice to have default
behave different than any other and than what 90% developers expects.



> --
> Álvaro Herrera                https://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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