Note in-line
--
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/seminar.html
Optimising Oracle Seminar - schedule updated Sept 19th
<sybrandb_at_yahoo.com> wrote in message
news:a1d154f4.0411250633.23ac34d6_at_posting.google.com...
>
> It doesn't use any index. Given the tiny number of rows, it is
> debatable whether using any index would be advantageous. You'll need
> at least 3 I/O requests for any index lookup,
Two at a minimum for an indexed table access -
index root (= leaf) block, table block.
> and probably
> you can
> read the entire table in memory with one single multiblock read.
>
But you first need to acquire the segment header, so it
could be two physical - and it WILL be a minimum of three
logical I/Os as the segment header is acccessed twice
before a tablescan (or index fast full scan).
Your premise that it is debatable is still correct - but for
frequent lookups, the debate swings heavily in favour of
using an index - especially if you are doing a simple PK
look up. Then even more in favour of an IOT, and then
if the circumstances are right a single table hash cluster.
> --
> Sybrand Bakker
> Senior Oracle DBA
Received on Thu Nov 25 2004 - 14:28:39 CST
