Re: FailedAssertion on partprune

On Mon, Aug 27, 2018 at 6:05 PM, Jonathan S. Katz <jkatz@postgresql.org> wrote:
> On behalf of the RMT, I just want to make sure this keeps moving along.
> It sounds like the next step is for Robert to verify that [3] is the
> expected
> behavior and then David can decide what to do from there.

Yes, that's the expected behavior.  If we didn't regenerate the paths
there, we'd end up with

Result
-> Append
 -> [various paths that produce a tlist which needs to be adjusted
later by the result node]

Instead of:

Append
-> [various paths that produce an adjusted tlist]

Paths of the former kind have already been generated; we regenerate
paths here to get the latter kind as well, which end up displacing the
old ones on cost.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company