Re: [ADMIN] pg_* Tables
Yep, small row counts. Thanks, Greg! From: Greg Williamson [mailto:gwilliamso...@yahoo.com] Sent: Monday, 6 December 2010 5:34 PM To: Samuel Stearns; pgsql-admin@postgresql.org Subject: Re: [ADMIN] pg_* Tables Samuel Stearns wrote: Howdy, Environment: Solaris 10 Postgres 8.3.3 I’m getting high sequential scans for some pg_* tables: database=# select relname, sum(seq_scan) as seq_scan,sum(seq_tup_read) as seq_tup_read,sum(idx_scan) as idx_scan, sum(idx_tup_fetch) as idx_tup_fetch, sum(n_tup_ins) as n_tup_ins, sum(n_tup_upd) as n_tup_upd, sum(n_tup_del) as n_tup_del from pg_stat_all_tables group by 1 order by 2 desc limit 4; relname | seq_scan | seq_tup_read | idx_scan | idx_tup_fetch | n_tup_ins | n_tup_upd | n_tup_del -+--+--+--+---+---+---+--- table | 6896498 | 91295702 | 107663 |469057 |103966 | 103966 |103966 pg_authid | 3119053 |125950392 | 12000732 | 12000718 | 1 | 1 | 0 pg_am | 2642438 | 2642440 |5 | 5 | 0 | 0 | 0 pg_database | 1349020 | 14771768 | 6953392 | 6953392 | 0 | 0 | 0 ... Is this normal? Is it advisable to index pg_* tables? Do you vacuum the database regularly ? What are the number of rows in those tables ? It is possible that the planner is doing a sequential scan because the tables are small and that's faster than doing indexed reads. Greg Williamson
[ADMIN] pg_* Tables
Howdy, Environment: Solaris 10 Postgres 8.3.3 I'm getting high sequential scans for some pg_* tables: database=# select relname, sum(seq_scan) as seq_scan,sum(seq_tup_read) as seq_tup_read,sum(idx_scan) as idx_scan, sum(idx_tup_fetch) as idx_tup_fetch, sum(n_tup_ins) as n_tup_ins, sum(n_tup_upd) as n_tup_upd, sum(n_tup_del) as n_tup_del from pg_stat_all_tables group by 1 order by 2 desc limit 4; relname | seq_scan | seq_tup_read | idx_scan | idx_tup_fetch | n_tup_ins | n_tup_upd | n_tup_del -+--+--+--+---+---+---+--- table | 6896498 | 91295702 | 107663 |469057 |103966 | 103966 |103966 pg_authid | 3119053 |125950392 | 12000732 | 12000718 | 1 | 1 | 0 pg_am | 2642438 | 2642440 |5 | 5 | 0 | 0 | 0 pg_database | 1349020 | 14771768 | 6953392 | 6953392 | 0 | 0 | 0 (4 rows) database=# Is this normal? Is it advisable to index pg_* tables? Thank you, Sam
Re: [ADMIN] pg_* Tables
Samuel Stearns wrote: Howdy, Environment: Solaris 10 Postgres 8.3.3 I’m getting high sequential scans for some pg_* tables: database=# select relname, sum(seq_scan) as seq_scan,sum(seq_tup_read) as seq_tup_read,sum(idx_scan) as idx_scan, sum(idx_tup_fetch) as idx_tup_fetch, sum(n_tup_ins) as n_tup_ins, sum(n_tup_upd) as n_tup_upd, sum(n_tup_del) as n_tup_del from pg_stat_all_tables group by 1 order by 2 desc limit 4; relname | seq_scan | seq_tup_read | idx_scan | idx_tup_fetch | n_tup_ins | n_tup_upd | n_tup_del -+--+--+--+---+---+---+--- - table | 6896498 | 91295702 | 107663 |469057 |103966 | 103966 |103966 pg_authid | 3119053 |125950392 | 12000732 | 12000718 | 1 | 1 | 0 pg_am | 2642438 | 2642440 |5 | 5 | 0 | 0 | 0 pg_database | 1349020 | 14771768 | 6953392 | 6953392 | 0 | 0 | 0... Is this normal? Is it advisable to index pg_* tables? Do you vacuum the database regularly ? What are the number of rows in those tables ? It is possible that the planner is doing a sequential scan because the tables are small and that's faster than doing indexed reads. Greg Williamson
