Re: Index Skip Scan - Mailing list pgsql-hackers

From Dmitry Dolgov
Subject Re: Index Skip Scan
Date
Msg-id CA+q6zcWd1EjYGpV9cqTU6S10rvu4LEVbGm_g_6yEA9LeH+afNA@mail.gmail.com
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In response to Re: Index Skip Scan  (Pavel Stehule <pavel.stehule@gmail.com>)
List pgsql-hackers
> On Tue, 9 Oct 2018 at 18:13, Pavel Stehule <pavel.stehule@gmail.com> wrote:
>
>> It looks like good idea, but then the node should be named "index scan" and
>> other info can be displayed in detail parts. It can be similar like "sort".
>> The combination of unique and index skip scan looks strange :)
>
> maybe we don't need special index skip scan node - maybe possibility to
> return unique values from index scan node can be good enough - some like
> "distinct index scan" - and the implementation there can be dynamic -skip
> scan, classic index scan,
>
> "index skip scan" is not good  name if the implementaion is dynamic.

Yeah, that's a valid point. The good part is that index skip scan is not really
a separate node, but just enhanced index only scan node. So indeed maybe it
would be better to call it Index Only Scan, but show in details that we apply
the skip scan strategy. Any other opinions about this?

>> I think it was query like
>> select count(*) from (select distinct x from tab) s

Thanks, I'll take a look.


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