Re: Fuzzy cost comparison to eliminate redundant planning

Tom Lane wrote:
> As an experiment, I made the attached patch that converts add_path's
> cost comparisons to "fuzzy" comparisons --- two paths are considered to
> have the same cost if it differs by less than 1% of the smaller
> total_cost.  I found that this reduced the planning time of Eric's
> query by about 40%, without changing the resulting plan.  On more
> typical queries where the relations all have different statistics,
> I doubt it would have as much effect, but I'm inclined to apply the
> change anyway.

It looks like a great idea to me...

 > + 	 * XXX does this percentage need to be user-configurable?

...but I think the answer to the above is yes.

Joe