How does Postgres make its B-tree index?
Masi,

The PostgreSQL B-Tree index is very strongly based on the implementation by Lehman and Yao, which includes a lot of work oriented around multi-version concurrency control, but there's still great info in this paper.

Of course, PostgreSQL doesn't make a 100% accurate replica of the method in the paper, and to find the differences, there will be almost no way to do it other than to (1) find someone who understands the PostgreSQL B-Tree, and has the time to go through the intricate explanation, or (2) dig through the source code yourself.

Another possibility is for you to visit Bruce Momjian's excellent reference website, where he discusses PostgreSQL internals in more detail.

In this case, however, based on the nature of your questions, I feel like you may have a fundamental misunderstanding about how B-Tree indexes work. In this case, I think a little Google searching, or maybe reading through a portion of a textbook like Fundamentals of Database Systems by Elmasri &amp; Navathe would do you some good.