Re: 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