On Thu, 2007-08-09 at 12:39 +0530, Pavan Deolasee wrote: > No, pruning removes all dead tuples, irrespective of whether they are > HOT or COLD updated and whether they are heap-only or not. It > handles line pointer redirection and marks > all dead tuples as ~LP_USED. Defragging just repairs the fragmentation > by rearranging LP_USED tuples. > > > It's easily possible that 100% of the cold updates and deletes > are > removed by defragging because of HOT updates. It would be > pointless to > trigger a VACUUM when it might find nothing to clear up. Its > also > possible that the deletes are at one end of the table and the > updates at > the other. So we really need to keep track of the effects of > defragging > dead cold updates and deletes, so they can be subtracted from > the cold > update + deletes.
Whether I got the exact details of frugging & depruning correct or not: if a tuple version is removed, then VACUUM doesn't need to remove it later, so any non-VACUUM removal of rows must defer a VACUUM. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 7: You can help support the PostgreSQL project by donating at http://www.postgresql.org/about/donate
