Re: Pizza Example
Date: Sun, 18 Apr 2004 23:36:50 +0100
Message-ID: <LbiFdpACMwgAFw7Q_at_thewolery.demon.co.uk>
In message <9Jugc.75998$vO4.5098632_at_phobos.telenet-ops.be>, Jan Hidders
<jan.hidders_at_REMOVETHIS.pandora.be> writes
>> Given a known primary key, it takes on average about 1.05 disk seeks
>>(excluding OS file management overhead) to retrieve a record. Given a
>>known index value, it takes a further 1.05 disk seeks to retrieve a
>>list of ALL primary keys associated with that value. Added to that, a
>>Pick record usually contains all data associated with an entity -
>>that would likely be scattered across multiple rows in multiple tables
>>requiring multiple seeks in a relational db.
>
>Sure. Retrieving records with an index is also very fast with DBM
>files. But what happens if you have a query with a couple of joins, a
>little aggregation and some subqueries?
Cheers,
Wol
-- Anthony W. Youngman - wol at thewolery dot demon dot co dot uk HEX wondered how much he should tell the Wizards. He felt it would not be a good idea to burden them with too much input. Hex always thought of his reports as Lies-to-People. The Science of Discworld : (c) Terry Pratchett 1999Received on Mon Apr 19 2004 - 00:36:50 CEST