Hi, I'm testing HOT patches, applying to CVS HEAD. http://archives.postgresql.org/pgsql-patches/2007-05/msg00065.php I found a few issues in the patch. Some of them might already have been fixed, but anyway I'll report them for information.
I don't see any problems excluding the following in TPC-C workload and pgbench power test. - MVCC-safe CLUSTER When I clustered a table with HOT-updated tuples, I saw the following error message. The HOT patch latest posted does not support MVCC-safe CLUSTER. | ERROR: unexpected HeapTupleSatisfiesVacuum result - Number of unremovable tuples reported by VACUUM VERBOSE HOT-updated tuples (HEAPTUPLE_DEAD_CHAIN) are counted as "keeped" and VACUUM VERBOSE prints them as "cannot be removed yet". However, we can actually remove them. We can reuse the data space of HOT-updated tuples, but need to keep their item pointers. We'd better to show them as two different messages -- for example, unremovable tuples and unreusable item pointers. - ANALYZE and statistics of dead rows Since redirected or redirect-dead item pointers are counted as "dead rows", we overestimates the number of dead rows. It confuses statistics and ill-affects to autovacuums; If autovacuum does ANALYZE, the number of dead tuples looks suddenly increased and it triggers unnecessary VACUUMs by the next autovacuum. - Trigger of auto-analyze HOT updates does not affect pgstat_info->trans->tuples_inserted/deleted fields, so auto-analyze will be triggered less frequently. However, it might be rather proper because HOT-updates means the indexed columns were not changed in the updates. If the values used in WHERE-clauses, we don't have to re-analyze the relation. Regards, --- ITAGAKI Takahiro NTT Open Source Software Center ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
