Tomas Vondra <tv@fuzzy.cz> writes:
> testdb=# select bt_page_items('test_index', 3);
> bt_page_items
> ----------------------------------
> (1,"(1,1)",8,f,f,"")
> (2,"(2,1)",12,f,f,"ca 01 00 00")
> (3,"(4,1)",12,f,f,"93 03 00 00")
> (3 rows)
> I don't understand the first row and I've been unable to find out if
> it's something special for the btree indexes or what.
You should read src/backend/access/nbtree/README, which would explain to
you why it is that leftmost tuples on interior btree pages don't contain
key values.
regards, tom lane