When _bt_check_unique finds a dead item that has same data as new
item, LP_DEAD is set to the item. Can we reuse this dead item instead
of inserting new item? If it is possible, the growth of btree index
can be reduced.
I think it is effective in the table like branches table of pgbench to
which the same item is updated many times.
An attached patch is test implementation of this idea. This patch is
not complete, but it might be useful to show this idea.
regards,
--- Atsushi Ogawa
