| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Thomas Kellerer <spam_eater(at)gmx(dot)net>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: 9.2 and index only scans |
| Date: | 2012-08-27 04:04:28 |
| Message-ID: | CAFj8pRBJayZDcQD66OvK9BhKknUN4bbVSdS1EK5vH-LmwnNqzg@mail.gmail.com |
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| Lists: | pgsql-general |
2012/8/26 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
>> is possible use seqscan for index?
>
> No, not for a normal indexscan --- concurrent page splits would break
> it.
>
and what about seq scan for prefetch index - and processing should be
random, but over pages in cache?
Pavel
> VACUUM can do that, mainly because it doesn't care if it visits some
> entries twice (and even then, it has to add a lot of pushups to ensure
> it doesn't miss any entries).
>
> regards, tom lane
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