Get Size of SeqScan data

seqscan.sql

-- 1- Data collect in a database, 2 times with few hours lag 
-- 2- 'Create table as' in another database

-- CREATE TABLE stats_tables AS
\o tables.out
COPY (
SELECT relid , schemaname , relname , seq_scan
       , seq_tup_read , idx_scan , idx_tup_fetch
       , pg_table_size(relid) as table_size
       , now() AS date_ev
FROM pg_stat_user_tables
WHERE pg_table_size(relid) > 8192 * 1024
ORDER BY seq_scan DESC
) TO STDOUT;
\o

-- 3- COPY data in the table, 2 times  
--  \copy stats_tables FROM 'tables.out'

-- 4- Run query  
SELECT tablename , nb_seq_scan_hours
  , pg_size_pretty((nb_seq_scan_hours * table_size )::numeric) AS total
  , pg_size_pretty((sum( nb_seq_scan_hours * table_size ) OVER ())::numeric) AS sum_size
FROM (
  SELECT tablename
         , trunc((seq_scan - prev_seq_scan)::float / lag_hours ) AS nb_seq_scan_hours
         , table_size
  FROM (
    SELECT schemaname || '.' || relname AS tablename , seq_scan
           , lag(seq_scan) OVER (PARTITION BY schemaname || '.' || relname ORDER BY date_ev) AS prev_seq_scan
           , date_ev
           , lag(date_ev) OVER (PARTITION BY schemaname || '.' || relname ORDER BY date_ev) AS prev_date_ev
           ,  extract('hours' from  date_ev - lag(date_ev) OVER (PARTITION BY schemaname || '.' || relname ORDER BY date_ev) )
             + extract('minute' from  date_ev - lag(date_ev) OVER (PARTITION BY schemaname || '.' || relname ORDER BY date_ev) ) / 60  as lag_hours
           , table_size
    FROM stats_tables) x
  WHERE prev_seq_scan IS NOT NULL
    AND seq_scan - prev_seq_scan > 0) y
ORDER BY 2 DESC;