| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: why not parallel seq scan for slow functions |
| Date: | 2017-11-08 12:26:16 |
| Message-ID: | CAA4eK1LjcXX2K0zS5sMTii+VOK7y1eGusHs7DKDkSQ17K3uL6Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Nov 8, 2017 at 4:34 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Tue, Nov 7, 2017 at 9:41 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>> This is required to prohibit generating gather path for top rel in
>> case of inheritence (Append node) at this place (we want to generate
>> it later when scan/join target is available).
>
> OK, but why don't we want to generate it later when there isn't
> inheritance involved?
>
We do want to generate it later when there isn't inheritance involved,
but only if there is a single rel involved (simple_rel_array_size
<=2). The rule is something like this, we will generate the gather
paths at this stage only if there are more than two rels involved and
there isn't inheritance involved.
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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