On Mon, Jun 18, 2018 at 4:05 PM, Peter Geoghegan <pg@bowt.ie> wrote:
> Finally, doing things this way would let you delete multiple
> duplicates in one shot, as I described in an earlier e-mail. Only a
> single descent of the tree is needed to delete quite a few index
> tuples, provided that they all happen to be logical duplicates. Again,
> your background worker will take advantage of this.
BTW, when you do this you should make sure that there is only one call
to _bt_delitems_vacuum(), so that there aren't too many WAL records.
Actually, that's not quite correct -- there should be one
_bt_delitems_vacuum() call *per leaf page* per bttargetdelete() call,
which is slightly different. There should rarely be more than one or
two calls to _bt_delitems_vacuum() in total, because your background
worker is only going to delete one heap page's duplicates per
bttargetdelete() call, and because there will be locality/correlation
with my TID order patch.
--
Peter Geoghegan