I do face the same problem when run a select on a Big Table with "TOP" clause.
The explain says "2) Next, we do an all-AMPs STAT FUNCTION step from ...."
I have observed that when I do a select like
"SELECT TOP 100 FROM table1;
It is taking a long time too to process and delays the entire process.
when I removed the TOP 100, it started working faster.
Is the TOP 100 is the clause invokes the STAT FUNCTION ?
On huge tables, why it delays?