Re: simple join uses indexes, very slow

On Tue, Mar 28, 2006 at 11:20:19AM -0600, Dave Dutcher wrote:
> I guess what I am really curious about is why was the OP getting an
> expensive sort when the planner tried a merge join?

A merge join requires sorted inputs.

> Most of the time was spent sorting the parameters parameters table by
> opset_num even though opset_num is indexed. Isn't Postgres able to walk the
> index instead of sorting?

The time of an index scan vs. a sequential scan + sort depends on several
factors, so it's not just a matter of walking the index whenever there is one.

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