Re: View's plan not taking advantage of WHERE?

Thanks Tom,

I've found other discussion of this, that aggregates foul-up the planner
with views.

GROUP BY & DISTINCT don't work, we're trying to grab a subset of records
and backfill any nulls to present a complete, single record... we're stuck
with a view as this is used by a Rails app.

We'll see what else we can come-up with.

Thanks again.

On Wed, Jun 5, 2013 at 9:16 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Mike Summers <msummers57(at)gmail(dot)com> writes:
> > Other than the tests in the original post do you have any suggestions?
>
> If you're speaking of
>
> http://www.postgresql.org/message-id/CAJGeMG89QbDxMab7-aPD_yXVsGx7Q=auXYM9UFVaq06cRZ4E2A@mail.gmail.com
> that has nothing to do with cached plans, obsolete or otherwise.
> You seem to be wishing that the planner would deduce "x = constant" from
> "aggregate_function(x) = constant", which is wrong on its face.
> AFAICS it's not even correct for the special case that the aggregate
> function is first_not_null(), since you have multiple occurrences of
> that in the view and there's no certainty that they all choose to return
> values from the same row.
>
> Even if the optimization is valid given some additional assumptions that
> you've not told us, it's going to be a sufficiently narrow case that
> I doubt we'd ever be willing to expend planner cycles on checking for it.
>
> If you want WHERE clauses to be pushed down into this query you need to
> think of some other way to define the query. Perhaps something
> involving GROUP BY or DISTINCT instead of first_not_null() would be more
> amenable to optimization.
>
> regards, tom lane
>