Re: How to analyze a slowdown in 9.3.5?

Just curious. Have you checked that the tables are being vacuum/analyzed periodically and that the statistics are up to date? Try running the following query to verify:

SELECT n.nspname,
       s.relname,
       c.reltuples::bigint,
--       n_live_tup,
       n_tup_ins,
       n_tup_upd,
       n_tup_del,
       date_trunc('second', last_vacuum) as last_vacuum,
       date_trunc('second', last_autovacuum) as last_autovacuum,
       date_trunc('second', last_analyze) as last_analyze,
       date_trunc('second', last_autoanalyze) as last_autoanalyze
       ,
       round( current_setting('autovacuum_vacuum_threshold')::integer + current_setting('autovacuum_vacuum_scale_factor')::numeric * C.reltuples) AS av_threshold
  FROM pg_stat_all_tables s
  JOIN pg_class c ON c.oid = s.relid
  JOIN pg_namespace n ON (n.oid = c.relnamespace)
 WHERE s.relname NOT LIKE 'pg_%'
   AND s.relname NOT LIKE 'sql_%'
 ORDER by 1, 2;