Re: bad estimates

Ken Geis wrote:
> I went through the code (7.4 beta2) that estimates the cost of an index
> scan path.  What I need to be sure of is that when running a query in
> pgsql that uses only the columns that are in an index, the underlying
> table need not be accessed.  I know that Oracle does this.

Thinking about it some more, it's obvious to me that a pgsql index scan
must be accessing the underlying table even though all of the
information needed is in the index itself.  A linear scan of a 660M file
should not take 55 minutes.  I could confirm this with stats, but
someone out there probably already knows the answer here.


Ken