Yep, small row counts. Thanks, Greg! From: Greg Williamson [mailto:[email protected]] Sent: Monday, 6 December 2010 5:34 PM To: Samuel Stearns; [email protected] 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
