autoanalyze criteria

Hi,

If I understand
http://www.postgresql.org/docs/9.1/static/routine-vacuuming.html
correctly, the autovacuum threshold in could be estimated like this in
PostgreSQL 9.1:

SELECT pg_stat_user_tables.relname,
pg_stat_user_tables.n_dead_tup,
CAST(current_setting('autovacuum_vacuum_threshold') AS bigint)
+ (CAST(current_setting('autovacuum_vacuum_scale_factor') AS
numeric)
* pg_class.reltuples) AS av_threshold
FROM pg_stat_user_tables
JOIN pg_class on pg_stat_user_tables.relid = pg_class.oid
ORDER BY 1;

If pg_stat_user_tables.n_dead_tup exceeds av_threshold autovacuum should
kick in. Obviously, that does rely on up-to-date statistics. Is that how
it is actually done?

2nd question: because pg_stat_user_tables.n_dead_tup is itself estimated
by ANALYZE it cannot be used as a criterion for the next autoanalyze
run, I think. Is there any way to query, whether a table currently
qualifies for autoanalyze?

Thanks and Regards,
Stefan