> So final question, what should I do to make that index much smaller on
> the disc.
Tune your penalty and picksplit function. Gevel module can help you to look
inside of index ( http://www.sai.msu.su/~megera/postgres/gist/gevel ).
Usially, index becomes big when picksplit works bad: during split it place one
key on one page and all other keys on another page. So you have a huge number of
page with single value.
--
Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru
WWW: http://www.sigaev.ru/