I could reproduce this on my laptop, standby is about 20% slower. I ran
oprofile, and what stands out as the difference between the master and
standby is that on standby about 20% of the CPU time is spent in
hash_seq_search(). The callpath is GetSnapshotDat() ->
KnownAssignedXidsGetAndSetXmin() -> hash_seq_search(). That explains the
difference in performance.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com