Re: BUG #4596: information_schema.table_privileges is way too slow

Hello

really it's should be slow, it's cross join pg_class, pg_authid, pg_authid

for fast respond you have to specify minimally table_name and grantor fields.

select * from information_schema.table_privileges where table_name =
'foo' and grantor = 'pavel';

regards
Pavel Stehule

2008/12/25, Kirill Simonov <xi(at)gamma(dot)dn(dot)ua>:
> Pavel Stehule wrote:
>> 2008/12/25 Kirill Simonov <xi(at)gamma(dot)dn(dot)ua>:
>>> Tom Lane wrote:
>>>> "Kirill Simonov" <xi(at)gamma(dot)dn(dot)ua> writes:
>>>>> It takes about 5 minutes to perform the query
>>>>> SELECT * FROM information_schema.table_privileges
>>>>> on an empty database (i.e. with system tables only).
>>>> Not here. What non-default settings might you be using?
>>>>
>>> Indeed, it is slow because there are a lot of rows in pg_authid (about
>>> 700).
>>> Is there a possibility to make table_privileges faster with a large
>>> number
>>> of roles?
>>>
>>> Thanks,
>>> Kirill
>>
>> two years ago I tested 50000 users without problems. Try to vacuum and
>> reindex your system tables
>>
>
> Neither VACUUM nor REINDEX SYSTEM did help. The problem could be
> reproduced on a freshly installed Postgres:
>
> -- add a function to generate dummy roles.
> create language plpgsql;
> create function create_dummy_role(start int, finish int) returns void as $$
> begin
> for i in start..finish loop
> execute 'create role dummy_' || cast(i as text);
> end loop;
> end;
> $$ language plpgsql;
>
> -- no extra roles
> select count(*) from information_schema.table_privileges;
> >>> Time: 11.467 ms
>
> -- 10 roles
> select create_dummy_role(1, 10);
> select count(*) from information_schema.table_privileges;
> >>> Time: 161.539 ms
>
> -- 100 roles
> select create_dummy_role(11, 100);
> select count(*) from information_schema.table_privileges;
> >>> Time: 7807.675 ms
>
> -- 1000 roles
> select create_dummy_role(101, 1000);
> select count(*) from information_schema.table_privileges;
> >>> Time: 543030.948 ms
>
>
> Thanks,
> Kirill
>