autovacuum

Hi

I have a table about 17G in size. I did a pg_relation_size before
deleting 2 millions rows. I waited a few hours(actually overnight) and
then checked the table size with pg_relation_size. The size reported was
exactly the same.

My autovacuum is set to run every 50 minutes.

Settings:

autovacuum = on # enable autovacuum subprocess?

autovacuum_naptime = 3000 # time between autovacuum runs,
in secs

autovacuum_vacuum_threshold = 10000 # min # of tuple updates before

# vacuum

autovacuum_analyze_threshold = 1500 # min # of tuple updates before

# analyze

autovacuum_vacuum_scale_factor = 0.4 # fraction of rel size before

# vacuum

autovacuum_analyze_scale_factor = 0.2 # fraction of rel size before

# analyze

autovacuum_vacuum_cost_delay = -1

vacuum_cost_delay = 200 # 0-1000 milliseconds

#vacuum_cost_page_hit = 1 # 0-10000 credits

#vacuum_cost_page_miss = 10 # 0-10000 credits

#vacuum_cost_page_dirty = 20 # 0-10000 credits

vacuum_cost_limit = 50

work_mem = 802400 # min 64, size in KB

maintenance_work_mem = 102400 # min 1024, size in KB

#max_stack_depth = 2048 # min 100, size in KB

# - Free Space Map -

max_fsm_pages = 2000000

Why doesn't pg_relation_size take the autovacuum maintenance into effect