Re: is rebuilding indexes necessary after import?
- From: "Richard Foote" <richard.foote@xxxxxxxxxxx>
- To: "Active DBA" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 23 Dec 2004 01:45:47 +1000
Comments below
----- Original Message -----
From: "stephen booth" <stephenbooth.uk@xxxxxxxxx>
To: <mark@xxxxxxxxx>
Cc: <sjaffarhussain@xxxxxxxxx>; "Active DBA" <oracle-l@xxxxxxxxxxxxx>
Sent: Wednesday, December 22, 2004 6:29 PM
Subject: Re: is rebuilding indexes necessary after import?
On Wed, 22 Dec 2004 02:37:25 -0500, Mark J. Bobak <mark@xxxxxxxxx> wrote:
> No, because import does not really "import" indexes. It issues a create
> index statement. So, the indexes are freshly built at the end of an
> import.
> -Mark
That begs the question, when is the create index statement issued?
'Create table, create index, import rows' and 'create table, import
rows, create index' could lead to different results in terms of index
efficiency. If the order of the data is such that the leading edge of
the index is monotonically increasing or decreasing then you'll
probably get an unbalanced and inefficient index (the same as you do
with any increasing indexed value) if the index is created before the
before the rows are imported and isn't reverse key.
Hi Stephen,
Monotonically increasing indexes do not become unbalanced and in the vast
majority of cases, don't become inefficient.
Please take a look at :
http://www.actoug.org.au/Downloads/oracle_index_internals.pdf
One day, the message will get through.
One day ...
Cheers
Richard
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