Should we add GUCs to allow partition pruning to be disabled?

David G. Johnston <david.g.johnston@gmail.com>

From: "David G. Johnston" <david.g.johnston@gmail.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, David Rowley <david.rowley@2ndquadrant.com>, Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-05-03T02:49:42Z
Lists: pgsql-hackers
On Wednesday, May 2, 2018, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:

> Robert Haas wrote:
> > On Wed, May 2, 2018 at 9:28 AM, Alvaro Herrera <alvherre@2ndquadrant.com>
> wrote:
> > > I admit I am more concerned about the possibility of bugs than I am
> > > about providing a performance-related tool.
> >
> > I agree that if partition pruning has bugs, somebody might want to
> > turn it off.  On the other hand, when they do, there's a good chance
> > that they will lose so much performance that they'll still be pretty
> > sad.  Somebody certainly could have a workload where the pruning
> > helps, but by a small enough amount that shutting it off is
> > acceptable.  But I suspect that's a somewhat narrow target.
> >
> > I'm not going to go to war over this, though.  I'm just telling you
> > what I think.
>
> Well, we didn't have a GUC initially, evidently because none of us
> thought that this would be a huge problem.  So maybe you're both right
> and it's overkill to have it.  I'm not set on having it, either.  Does
> anybody else have an opinion?
>

I toss my +1 to removing it altogether.

David J.

Commits

  1. Tweak partitioning documentation wording

  2. docs: Rework sections on partition pruning/exclusion

  3. Add GUC enable_partition_pruning