[erlang-questions] Index Overhead In Mnesia

[Ben Hood]

Hynek,

On 10 Jun 2008, at 13:46, Hynek Vychodil wrote:

> It is not obvious, but try change your write:
>
> write(_,0) -> ok;
> write(X,N) ->
>     T = now(),
>     mnesia:write(X#a{id = T, first = T, second = T}),
>     write(X,N-1).
>
> and think what happened to indexes in previous version :-)

Very interesting!

So, if I understand you correctly, what I conclude is that the index  
performance degrades when you have lots of identical keys.

Do you know why this is the case?

Does the index perhaps maintain a list of values for each key and  
hence the set of values has to be updated continuously?

If so, is this a bug or a feature?

Thx,

Ben