On Wed, Mar 21, 2012 at 8:13 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > I wrote: >> Robert Haas <robertmh...@gmail.com> writes: >>> Specifically, I'm wondering if we couldn't get away with rearranging >>> things so that the root line pointer (which has index entries) points >>> to the actual tuple, and the other line pointer (which can't have any >>> index entries) gets marked UNUSED. > >> This would amount to changing the TID of the live row. > > Another issue, quite independent from race conditions against other > observers of the row, is what if the tuple is part of an update chain? > You have no way to find the predecessor row version and update its > t_ctid forward link.
I don't see why I need to. The predecessor, if any, points to the root of the HOT chain; and that's exactly the TID that I'm proposing to keep around. The heap-only tuple's TID gets canned, but nobody can be pointing to that from outside the block, IIUC. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
