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Re: Anyone seen any independent performance .....

From: Stephane Faroult <>
Date: Thu, 05 Sep 2002 13:38:44 -0800
Message-ID: <>

Benchmarks I have carried out one year ago on Oracle 8.1.7 point to slightly better (but of the same order of magnitude) results. If the number of blocks accessed when inserting into a 'naked' table was 100, the definition of a (sequence based) primary key was adding 240, and each additional index about 257, whether it was based on a number or a string. In terms of elapsed time however the picture was a little bit brighter, as the PK was adding around 85 and each index around 135. The number of distinct keys for a non-unique index doesn't seem to make any difference. I also noticed that adding a foreign key was adding 190 in terms of accessed blocks (non-indexed FK, just the cost of checking the constraint), but nothing measurable in terms of elapsed time. Interestingly, a trigger to maintain a total in a different table was costing hardly more than an index.

> "Jamadagni, Rajendra" wrote:
> I don't remember where but the results of the study were like
> following ...
> if the cost of inserting one row to a table is 1 unit and if you have
> 5 indexes on the table than total cost of inserting 1 row to the table
> is
> 1 (cost of inserting a row)
> + 3*5 (5 indexes)
> ---------
> 16
> So total cost is about 16 units.
> Raj

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Author: Stephane Faroult

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Received on Thu Sep 05 2002 - 16:38:44 CDT

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