On Fri, Jul 19, 2013 at 5:08 PM, guxiaobo1982 <guxiaobo1...@qq.com> wrote:
>
> what does a wrapper function mean, count is a standard function in Greenplum,
> or how to creat the wrapper function.
>
> regards
>
> On Fri, Jul 19, 2013 at 7:47 AM, guxiaobo1982 <guxiaobo1...@qq.com> wrote:
>
> There is another situation,
>
>
> We have a demo table with about 17000000 rows, the "select count(1) from
> demotable" statement finishes with-in 3 seconds when executed directlly
> against the Greenplum database,but it takes about 230 seconds to finish when
> executed via postgres_fdw inside PostgreSQL 9.3 beta2, I guess that it may
> because of postgres_fdw pulling data to the PostgreSQL instance and counts
> the rows there, but I think the query optimizer should pass through the
> count() function to the Greenplum end, and gets only the result back.
>
>
> Are you able to create a function in Greenplum which is a wrapper around that
> count(*) and call that via the postgres_fdw?
>
Create a function in Greenplum like (untested, I don't have Greenplum)
create table custom_count() returns bigint as $$
select count(*) as total from yourtable;
$$ language sql;
Then from your pg db using postgres_fdw select * from that function (which
resides in Greenplum).
No idea if that'll work or make a difference though.
