really thanks,Teodor Sigaev. HOW ts2 implment that ?

really thanks for Teodor Sigaev,beat regards.
Becaue it's very importent or me these days,so I posted it again.

>> I only know that GiST is also "Inverse Order OF Idexing",but of course
>> it is a tree NOT as lucene does
>Tsearch2 doesn't use inverted index (yet), and so it easy to update (your index
>is always full - online indexing), but it hasn't good performance on large data
>set. The limit is about 10^5 - 10^6 rows in practice.

I know the LUCENE " inverted index " is just like follows:

keyword doc_id[frequence] location
guangzhou 1[2] 3，6
he 2[1] 1
i 1[1] 4
live 1[2],2[1] 2，5，2
shanghai 2[1] 3

so ,before I thought that A node In GiST tree is very like the above :
In the tree's node , it has several value for storing its's
turple_id[frequence] location ,and that is why I thoutht the " inverted index ".


BUT now , I'm lost again ,how does Gist tree store lexem and how to find his correspoding tuples in database( including frequence location)?


Or to say ,how TSearch2 implement the Lucene's "inverted index" mean ?