[GENERAL] large table

[Luke Coldiron]

I am trying to figure out what would have caused a table in a PostgreSQL 8.4.16 
to get into a state where there is only 1 live tuple and has only ever had one 
1 tuple but the size of the table is huge.

CREATE TABLE public.myTable(  myColumn timestamp with time zone NOT NULL);

Note: there is no primary key or index on this table.
CREATE OR REPLACE FUNCTION public.myFunc()RETURNS VOID AS $$BEGIN   UPDATE 
public.myTable SET myColumn = CLOCK_TIMESTAMP();
   IF NOT FOUND THEN      INSERT INTO public.myTable(myColumn) VALUES 
(CLOCK_TIMESTAMP());   END IF;END;$$ LANGUAGE plpgsql VOLATILE STRICT SECURITY 
DEFINER;
CREATE OR REPLACE FUNCTION public.wasUpdated(OUT was_updated boolean)RETURNS 
BOOLEAN AS $$BEGIN   was_updated := COALESCE((SELECT myColumn FROM 
public.myTable) > (CLOCK_TIMESTAMP() - INTERVAL '5 SECOND'),                    
                                 FALSE);END;$$ LANGUAGE plpgsql VOLATILE STRICT 
SECURITY DEFINER;
SELECT *FROM pg_stat_all_tablesWHERE relname = 'myTable';


 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  relid
  schemaname
  relname
  seq_scan
  seq_tup_read
  idx_scan
  idx_tup_fetch
  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
 
 
  16713
  public
  myTable
  3991833
  3992001
   
   
  0
  3775409
  0
  3771173
  949135
  183
   
  2014-09-18
  11:28:47.63545+00
   
  2014-09-18
  11:27:47.134432+00
 
The stats are very far off with n_live_tup at 949135 when there is only a 
single row in the table. Autovacuum appears to be running on a regular basis.
SELECT *
FROM pgstattuple('public.myTable');


 
 
 
 
 
 
 
 
 
 
  table_len
  tuple_count
  tuple_len
  tuple_percent
  dead_tuple_count
  dead_tuple_len
  dead_tuple_percent
  free_space
  free_precent
 
 
  34709504
  1
  32
  0
  105
  3360
  0.01
  30757308
  88.61
 
The actual size of the table is around 33 MB.
The myFunc function is called every 2.5 seconds and the wasUpdated function 
every 2 seconds by separate processes. 
I realize that running a FULL VACUUM or CLUSTER command on the table will 
resolve the issue but I am more interested in a root cause that explains why 
this table would end up in this state. I have tried to reproduce this issue by 
running the exact setup and have not been able to get the table to grow like 
this example. Any plausible cause'es or explanations would be much appreciated.
Luke