| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
| Cc: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: why partition pruning doesn't work? |
| Date: | 2018-06-08 03:22:51 |
| Message-ID: | 21787.1528428171@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
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.
regards, tom lane
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