Re: MVCC and index-only read

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От Jonah H. Harris
Тема Re: MVCC and index-only read
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Msg-id 36e682920811181158q6d712784t20d7465ac3601fac@mail.gmail.com
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Ответ на Re: MVCC and index-only read  (Thomas Kellerer <spam_eater@gmx.net>)
Ответы Re: MVCC and index-only read  (Thomas Kellerer <spam_eater@gmx.net>)
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On Tue, Nov 18, 2008 at 2:33 PM, Thomas Kellerer <spam_eater@gmx.net> wrote:
> If all the columns from the select list are available in the index, then
> Oracle will always prefer the index scan over a table scan (at least I have
> never seen something else). Even for a SELECT that returns all rows of the
> table.

No, it doesn't always prefer index fast full scan.

> They are taking this concept even further with index organized tables, where
> no real "table data" exists, everything is stored in the index (quited nice
> for e.g. link tables that only consist of two or three integer columns)

Those are essentially clustered indexes, and they're not quite stored
exactly the same..

--
Jonah H. Harris, Senior DBA
myYearbook.com

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