Could the index of dovecot be stored in database?

[eSX]

Hi dovecot,
I have a question about the index of dovecot.
I had read the wiki, and saw that I can custom a Input streams to do
read/seek/sync...by implementing a istream-*.c file.
Thus maybe dovecot can read mail from a http server or any others.
But I found that the index of maildir can't extend very well.
There is no extern API for developer?
For example, I want to put the index to database(maybe, MySQL) or any else,
But I found I have no way to implement it, Unless a heavy modification?


-- 
eSX