Duplicate index check in btbuild

Hi all,

Currently btbuild() rejects duplicate index in comparetup_index().
But there are some cases that index tuples for already deleted
heap tuples should be made. comparetup_index() doesn't work
well in such cases because comparetup_index() couldn't ignore
deleted tuples. In addition I could find no other place to check
index uniqueness in tuplesort.c .
Seems we have to give up the uniqueness check in comparetup_
index() and have to check it in _bt_buildadd().
We would be able to take the visibility of heap tuples into acount
in _bt_buildadd(). 

Comments ?

Regards.

Hiroshi Inoue
Inoue@tpf.co.jp