Horton

Re: Assertion failure with LEFT JOINs among >500 relations

David Rowley <dgrowleyml@gmail.com>

View thread View on postgr.es
From: David Rowley <dgrowleyml@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Onder Kalaci <onderk@microsoft.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2020-10-19T11:09:08Z
Lists: pgsql-hackers 
On Mon, 19 Oct 2020 at 13:06, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> David Rowley <dgrowleyml@gmail.com> writes:
> > I guess we could resolve that concern by just changing the failing
> > assert to become: Assert(outer_skip_rows <= outer_rows ||
> > isinf(outer_rows));
>
> I can't really object to just weakening the Assert a tad.
> My thoughts would have run towards checking for the NaN though.

I ended up back-patching a change that does that.

Thanks for your input on this and for the report, Onder.

David

Commits

  1. Relax some asserts in merge join costing code

  2. Prevent overly large and NaN row estimates in relations

  3. Avoid a couple of zero-divide scenarios in the planner.

  4. Guard against incoming rowcount estimate of NaN in cost_mergejoin().

  5. When a relation has been proven empty by constraint exclusion, propagate that