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-- CHECK CACHE RATE --
SELECT 
  sum(heap_blks_read) as heap_read,
  sum(heap_blks_hit)  as heap_hit,
  sum(heap_blks_hit) / (sum(heap_blks_hit) + sum(heap_blks_read)) as ratio
FROM 
  pg_statio_user_tables;


-- CHECK INDEX USAGE ---
SELECT 
  relname, 
  100 * idx_scan / (seq_scan + idx_scan) percent_of_times_index_used, 
  n_live_tup rows_in_table
FROM 
  pg_stat_user_tables
WHERE 
    seq_scan + idx_scan > 0 
ORDER BY 
  n_live_tup DESC;


-- CHECK INDEX IN CACHE --
SELECT 
  sum(idx_blks_read) as idx_read,
  sum(idx_blks_hit)  as idx_hit,
  (sum(idx_blks_hit) - sum(idx_blks_read)) / sum(idx_blks_hit) as ratio
FROM 
  pg_statio_user_indexes;


--QUERY TIME --

SELECT 
  (total_time / 1000 / 60) as total_minutes, 
  (total_time/calls) as average_time, 
  query 
FROM pg_stat_statements 
ORDER BY 1 DESC 
LIMIT 100;