I've been periodically collecting the stats stored in pg_statio_all_tables and pg_stat_database for ~30 different clusters, and have noticed a curiosity. I would have thought that for a given period, the change in pg_stat_database.blks_read would be <= the sum of the changes in pg_statio_user_tables.heap_blks_read + pg_statio_user_tables.idx_blks_read + pg_statio_user_tables.toast_blks_read + pg_statio_user_tables.tidx_blks_read. In short, the total would be <= heap + idx + toast + idx for user tables. It does not appear that way. The table-level IO stats appear to be typically 1-2 orders of magnitude larger than the db-level stats. Can anyone explain that? TIA. Ed
