RE: RMAN impact
- From: Tanel Poder <tanel.poder.003@xxxxxxx>
- To: pythianbrinsmead@xxxxxxxxx, 'Jared Still' <jkstill@xxxxxxxxx>
- Date: Sat, 28 Oct 2006 11:44:47 +0800
Primary key does not imply an index... indexed primary key is just a
performance feature.
In Oracle RDBMS they have made it mandatory, but the only reason for that is
performance, there is no fundamental need to have an index on primary key
column(s).
Oracle has solved it using a B-tree derivative, others (like TimesTen) have
solved it using hash index, others might be using yet another approach.
That's the physical layer.
So, indexing, including primary key indexing should be responsibility of
DBA/physical designer role, not data modeler role (unless, as Jared said,
the data modeler happens to be a DBA too).
Of course a very good data modeler should at least be aware of the
implications of physical layer, just as a very good DBA must understand the
OS below the databases.
Tanel.
_____
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Mark Brinsmead
Sent: Saturday, October 28, 2006 10:54
To: Jared Still
Cc: Christian Antognini; oracle-l@xxxxxxxxxxxxx
Subject: Re: RMAN impact
True enough! Sort of. Except that a primary key implies an index. As does
a foreign key. (Actually, unless you're crazy, many foreign keys will imply
two indexes, one on each table.)
Conversely, no indexes means no primary keys. In my personal fantasy world,
lack of Primary Keys means unemployed data modelers, but sadly the so-called
real-world seems to be quite different... ;-)
A (logical) data model may not specify indexes, but if it's done correctly,
it's going to imply at least one on every table. If the physical data model
fails to embody those indexes, then somebody ought to be in trouble! ;-)
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