[erlang-questions] Call for Contributions: Mnesia best practices

[Bob Calco]

Everyone:

I'm looking for thoughts from fellow Erlangers about database design &
implementation in Mnesia. With a heavy SQL background I, like many
relatively new Erlang folks I'm sure, have a tendency to think in terms of
the capabilities of traditional RDBMSs, and to try to normalize every data
model with which I come into contact. 

I'm also used to letting administrators deal with most database operations
and issues, whereas with Mnesia the programmer has basically supreme control
(both to do some really cool and flexible things, and to do some really dumb
things).

So the question is generic, not intended to solve a specific problem. I have
some ideas and will contribute separately. 

The question is: What is the best advice you could give a data architect
about designing and implementing a database in Mnesia from scratch? Examples
of the kinds of issues I'd like to see folks address:

* How to create an optimal data model for performance (vs. reporting,
comparing the SQL way to the Mnesia way). This question is really about
normalization in Mnesia vs. SQL, and tricks like storing whole records in
table fields.

* How to partition data between subsystems, without losing the illusion
they're all one big happy system.

* How to handle complex clustering and failover scenarios.

* How to handle calculation-intensive databases (for example, stock
databases that need to constantly recalculate certain attributes for the
purposes of sorting, searching)

* How to handle complex domain relationships. For example, let's say you are
writing a CRM tool and want to store each "person" in the database. But each
person can also be a colleague, or a client, or an incidental character
(contact person at some organization). E.e, What do you do when there is
inheritance in your domain model?

* What are some current pitfalls or "weak spots" of Mnesia that ought to be
avoided, however tempting they might be?

* How to implement the various callbacks, and what kinds outside of those
described in the Mnesia documentation, have been found most useful in
practice?

That kind of thing. I want to put together something of a master knowledge
base on this big subject that the community can use both to promote Erlang
and to promote Erlang's "best practices" implementation in the important
area of serving data to applications. 

/Bob