Mnesia and Oracle

Yariv Sadan <>
Tue Aug 8 23:51:54 CEST 2006


Hi Eduardo,

I haven't had production experience with these databases, but there
are a couple of things I found by research that are keeping me from
using Mnesia exclusively in my application:

- Mnesia disc storage, based on dets, has a couple of drawbacks when
handling very large (many gigs) datasets: potentially long repair
times and memory consumption that grows with data fragmentation.
- QLC, the query engine for Mnesia, doesn't currently optimize joins.
If your queries involve joining big tables, they can take a long time
to execute.

The join optimizations are planned for a future R11 OTP release, but
there are no plans to change dets AFAIK.

Depending on your application, these issues may not be a big problem.
For the application I'm building, I'm planning on using both MySQL and
Mnesia, where MySQL will be used for storing high-volume data and
Mnesia for "live" session data.

Hope this helps!

Regards,
Yariv

On 8/8/06, Inswitch Solutions <> wrote:
>
>
>
> Hi,
>
> I'm already working with Oracle and Mnesia, and I'd  like to hear experiences of the Erlang community about these  databases.
> When deciding over Oracle or Mnesia database for an  Erlang, or non Erlang, based real-time system which factors are in favour  in one over the other (performance...?) ?.
>
>
> thanks, Eduardo
>
>
>
>
>
> Prepaid Expertise -        Programmable Switches
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> Eng.        Eduardo Figoli - Development Center - IN Switch Solutions        Inc.
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