Re: why partition pruning doesn't work?

On 8 June 2018 at 15:22, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> writes:
>> On 8 June 2018 at 03:43, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> Maybe there's something I'm missing here, but I sort of hoped that this
>>> patch would nuke all the special-case code for Params in this area.
>>> Why is there any need to distinguish them from other stable expressions?
>
>> We need to know which Params exist in the Expr as if there are no
>> Params, or only external Params, then we can run-time prune during
>> startup of the executor.
>
> This does not refute my question. Why doesn't the same logic apply
> to any stable expression? That is, ISTM a Param is a special case
> of that.

Okay, maybe we don't need to know which external params exist, but we
need to know if there are any exec params so that we don't try to
evaluate an expression with any of those during executor startup.

I'll produce a patch which simplifies things in that area.

Thanks for looking at this.

--
David Rowley http://www.2ndQuadrant.com/
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