volunteer wanted to write a few FAQ entries about Mnesia

[Laszlo Varga]

Hello,
from my little practice, I have the feeling that the explicit concept
depends on the task, what the aggregate keys are intended to used for.
You might need them for reordering, for augmentation, for table extension,
for modelling hiearchial data structures, or whatelse.
Through my eyes, SNMP is not a concept, but a bunch of allowed concepts,
so difficult to generalize.

Laszlo Varga





> From: Chandrashekhar Mullaparthi <Chandrashekhar.Mullaparthi@REDACTED>
> To: "'Chris Pressey'" <cpressey@REDACTED>, Ulf Wiger 
<etxuwig@REDACTED>
> Cc: matthias@REDACTED, erlang-questions@REDACTED
> Subject: RE: volunteer wanted to write a few FAQ entries about Mnesia
> Date: Mon, 24 Feb 2003 12:58:13 -0000
> MIME-Version: 1.0
> 
> mnesia:match_object 
> mnesia:select 
> 
> achieve this, but you are right, there is no explicit concept of aggregate
> keys.
> 
> Chandru
> 
> -----Original Message-----
> From: Chris Pressey [mailto:cpressey@REDACTED]
> Sent: 21 February 2003 22:05
> To: Ulf Wiger
> Cc: matthias@REDACTED; erlang-questions@REDACTED
> Subject: Re: volunteer wanted to write a few FAQ entries about Mnesia
> 
> 
> On Fri, 21 Feb 2003 11:53:02 +0100 (MET)
> Ulf Wiger <etxuwig@REDACTED> wrote:
> 
> > On Thu, 20 Feb 2003, Chris Pressey wrote:
> > 
> > >Records are accessed by a single key (which may be unique
> > >or duplicate) and there is no concept of a secondary key.
> > 
> > Actually there is. You can define an index on a non-key
> > attribute, and access records using mnesia:index_read/3 or
> > index_match_object/2.
> 
> Oops!  I meant there is no concept of an aggregate key, i.e. of using
> multiple fields to identify a record.
> 
> -Chris
> 
> 
> 
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