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 -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers