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
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