with PostgreSQL 9.1.9,the stats collector process is not work!

Hello everybody:

After I switch the slave to the master , I can not get the stats information by the below sql and the pg_stat_reset() does not work on the New Master,
And I vacuum by hand,it's still not work! I need some help.Could you give me any idea?

the stat sql:

SELECT st.relname, n_tup_ins, n_tup_upd, n_tup_del, n_tup_hot_upd, n_live_tup, n_dead_tup, last_vacuum, last_autovacuum, last_analyze, last_autoanalyze, vacuum_count, autovacuum_count, analyze_count, autoanalyze_count, pg_size_pretty(pg_relation_size(st.relid) + CASE WHEN cl.reltoastrelid = 0 THEN 0 ELSE pg_relation_size(cl.reltoastrelid) + COALESCE((SELECT SUM(pg_relation_size(indexrelid)) FROM pg_index WHERE indrelid=cl.reltoastrelid)::int8, 0) END + COALESCE((SELECT SUM(pg_relation_size(indexrelid)) FROM pg_index WHERE indrelid=st.relid)::int8, 0)) AS size FROM pg_stat_all_tables st JOIN pg_class cl on cl.oid=st.relid WHERE schemaname = 'public' ORDER BY relname;

My environment:

Linux 3.2.1-gentoo-r2
postgresql 9.1.9,

the paras:
"autovacuum";"on"
"track_counts";"on"

/etc/hosts:
127.0.0.1 localhost 192.168.0.22 localhost.localdomain localhost

the postgresql's processes exist:

writer process stats collector process wal writer process autovacuum launcher process wal sender process

Thank you for your time!
Best Regard!

River