Re: index full scan over an index fast full scan in an analytic f

Hi!

You can't have ascending nor descending indesc fast full scans. This (asc/desc) only works with range or regular full scans.

Tanel.

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Saturday, October 25, 2003 4:59 AM

> But the fact is, the access path is still a valid path if the user needs
the
> data returned ordered on the indexed columns.
> Index_asc or Index_desc should do the job without extra cost.
>
> Waleed
>
> -----Original Message-----
> Sent: Friday, October 24, 2003 9:39 PM
> To: Multiple recipients of list ORACLE-L
> function?
>
>
> Tanel
>
> Tanel Poder wrote:
> > As an addition to Vladimir's response:
>
> I cannot provide you with detailed information -- can only give pointers
> to the documentation -- otherwise it would look suspicious :)
>
> > Full scan will search from index root block using branch blocks to first
> > leaf block. And since all leaf blocks have pointers to next and previous
> > leaf block in index, sequentially reading only leaf blocks is sufficient
> for
> > returning all values in index, in order (keys are ordered inside leaf
> blocks
> > as well).
> >
> > FFS will scan from index header block (note that index segment header
and
> > index root block are different ones) up to segment high water mark using
> > multiblock reads and ignoring contents of root, branch, bitmap, extent
> map,
> > freelist group blocks. Rows are returned as they've read from blocks,
thus
> > no order can be guaranteed.
>
> "Rows are returned as they've read from blocks, thus no order can be
> guaranteed."
>
> Not rows, but blocks returned as is in order they being read. Keys (rows)
> are ordered inside leaf blocks -- as you wrote above. So, inside the
blocks
> the order is consistent but blocks are 'mixed' whilst read.
>
> Things (parameters etc.) are changing, as Cary pointed out, principles are
> not.
> --
> Vladimir Begun
> The statements and opinions expressed here are my own and
> do not necessarily represent those of Oracle Corporation.
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Vladimir Begun
> INET: Vladimir.Begun_at_oracle.com
>
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> Author: Khedr, Waleed
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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