Search Postgresql Archives

pg_class.reltuples VS pg_stat_all_tables.n_live_tup for estimation of table

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hello,

Does anyone which is a more accurate estimate of a table's live rows: pg_class.reltuples (http://www.postgresql.org/docs/current/static/catalog-pg-class.html) OR pg_stat_all_tables.n_live_tup (http://www.postgresql.org/docs/current/static/monitoring-stats.html#PG-STAT-ALL-TABLES-VIEW)? In my test database their values are not the same.
  • Is pg_class.reltuples an estimation of live tuples only, or is it of all tuples (both live and dead)? I would guess it's live only but that is a guess
  • In the database I am testing:
    • pg_class.reltuples <> pg_stat_all_tables.n_live_tup
    • pg_class.reltuples <> (pg_stat_all_tables.n_live_tup + pg_stat_all_tables.n_dead_tup)

I understand that pg_stat_all_tables is probably the more expensive view to query but I am already querying both so I only care which is more accurate.


Thanks!
Will

Will J. Dunn

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]
  Powered by Linux