Note in-line.
--
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
April 2004 Iceland http://www.index.is/oracleday.php
June 2004 UK - Optimising Oracle Seminar
"Ed Stevens" <ed.stevens_at_comcast.net> wrote in message
news:1512dfb8.0403310828.7c4cec55_at_posting.google.com...
> "(Of course, you may have created data where the first row, when
> ordered by pk, was not the first row in the table - but I'm assuming
> you didn't)."
>
> Why would you assume that?
>
Because to start with I assumed you were smart enough to
have worked the answer out for yourself if that had been the
problem. Then the moment I hit SEND I realised that it was
irrelevant anyway, but didn't bother to send a correction. I took
'lowest' to mean 'appearing first in the output' for just long
enough
to add the final unnecessary comment.
> Actually, that gets to what I was trying to prove out when I noticed
> the "unaccounted for" blocks. (Another 'animated discussion' with my
> partner.) The table was loaded with a series of INSERTs inside a loop,
> using the random function to populate the PK. At that point, a SELECT
> . . ORDER BY block, row showed that the PK was scattered randomly
> across the blocks. I then did an exp/imp and then SELECT . . . ORDER
> BY prim_key. My partner said he knew "for a fact" that the import
> would physically sequence the rows by PK. (as if that meant
> anything). Unless I missed something, the rows were just as randomly
> distributed after the import as before.
>
In general they ought to be. For most of the last N years, exp has
just done a 'select * from table' to export the data, and that isn't
likely to use the PK to re-arrange the data.
It's probably possible to make it happen in more recent versions
of Oracle if the table has become sparse, and you use the option
for adding a WHERE clause to the export that makes Oracle walk
the PK index to reach the data because the CBO says that's the
cheapest option.
Received on Wed Mar 31 2004 - 11:21:13 CST
