"big_mafa" <big_mafa@freemail.hu> writes:
> So, I realized, that PostgreSql doesn't truncates the xlog
> automatically.
Sure it does. However, the default allocation unit for xlog is 16MB,
so you're not going to be able to do anything in "a few MB".
You could try reducing the xlog allocation unit to a meg or two, but
I'm not sure exactly how much you'd have to change (it's probably not
a one-liner, because we don't officially support alternative sizes).
I'm also not sure that performance would be good if you did.
If you need a database with a tiny disk footprint, you might want to
look at Berkeley DB, or something else designed to be an embedded
database.
regards, tom lane