can postgres btree indexes shrink?

[Azad Bolour <azadbolour@xxxxxxxxxx>]

Does the postgres implementation of btrees shrink the index if adjacent index tree nodes can be combined? 

I have read that data pages are not coalesced, only garbage collected when they become empty. But I have not seen anything specific about the treatment of index pages as deletions make the tree more sparse.

Thanks.

Azad