Re: [HACKERS] subquery in limit
> "Roberts, Jon" <[EMAIL PROTECTED]> writes: > > I have no idea why you can't do a subquery in the limit > > It hasn't seemed worth putting any effort into --- AFAIR this is the > first time anyone's even inquired about it. As you say, you can always > use a function. > > > And I'm sure someone will point out a more efficient way to write my > > function without using pl/pgsql. :) > > Only that it doesn't seem a particularly bright idea to use SECURITY > DEFINER for a function that will execute any arbitrary caller-provided > SQL ... > LOL! I knew something in my code would trigger a response. :) Jon ---(end of broadcast)--- TIP 6: explain analyze is your friend
Re: [HACKERS] subquery in limit
"Roberts, Jon" <[EMAIL PROTECTED]> writes: > I have no idea why you can't do a subquery in the limit It hasn't seemed worth putting any effort into --- AFAIR this is the first time anyone's even inquired about it. As you say, you can always use a function. > And I'm sure someone will point out a more efficient way to write my > function without using pl/pgsql. :) Only that it doesn't seem a particularly bright idea to use SECURITY DEFINER for a function that will execute any arbitrary caller-provided SQL ... regards, tom lane ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
Re: [HACKERS] subquery in limit
I have no idea why you can't do a subquery in the limit but you can
reference a function:
create table test as select * from pg_tables;
create or replace function fn_count(p_sql varchar) returns int as
$$
declare
v_count int;
begin
execute p_sql into v_count;
return v_count;
end;
$$
language 'plpgsql' security definer;
select * from test limit fn_count('select round(count(*)*0.9) from
test');
And I'm sure someone will point out a more efficient way to write my
function without using pl/pgsql. :)
Jon
> -Original Message-
> From: [EMAIL PROTECTED] [mailto:pgsql-hackers-
> [EMAIL PROTECTED] On Behalf Of Grzegorz Jaskiewicz
> Sent: Friday, February 15, 2008 5:35 AM
> To: pgsql-hackers@postgresql.org
> Subject: [HACKERS] subquery in limit
>
> (just as an example):
> select * from test order by a limit (select count(*)*0.9 from test);
>
> is not doable in postgresql. Someone recently asked on IRC about,
> "SELECT TOP 90 PERCENT" type of query in m$sql.
> Any ideas how should this be approach in psql. I ask here, because you
> guys probably can tell why the first query won't work (subquery is not
> allowed as limit's argument, why?).
>
> cheers.
>
> --
> Grzegorz Jaskiewicz
> [EMAIL PROTECTED]
>
>
>
>
> ---(end of
broadcast)---
> TIP 3: Have you checked our extensive FAQ?
>
>http://www.postgresql.org/docs/faq
---(end of broadcast)---
TIP 2: Don't 'kill -9' the postmaster
[HACKERS] subquery in limit
(just as an example): select * from test order by a limit (select count(*)*0.9 from test); is not doable in postgresql. Someone recently asked on IRC about, "SELECT TOP 90 PERCENT" type of query in m$sql. Any ideas how should this be approach in psql. I ask here, because you guys probably can tell why the first query won't work (subquery is not allowed as limit's argument, why?). cheers. -- Grzegorz Jaskiewicz [EMAIL PROTECTED] ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
