Re: PoC: Partial sort

On Sun, Dec 22, 2013 at 07:38:05PM +0400, Alexander Korotkov wrote:
> Hi!
> 
> Next revision. It expected to do better work with optimizer. It introduces
> presorted_keys argument of cost_sort function which represent number of
> keys already sorted in Path. Then this function uses estimate_num_groups to
> estimate number of groups with different values of presorted keys and
> assumes that dataset is uniformly divided by
> groups. get_cheapest_fractional_path_for_pathkeys tries to select the path
> matching most part of path keys.
> You can see it's working pretty good on single table queries.

Nice work! The plans look good and the calculated costs seem sane also.

I suppose the problem with the joins is generating the pathkeys?

Have a nice day,
-- 
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> He who writes carelessly confesses thereby at the very outset that he does
> not attach much importance to his own thoughts.
   -- Arthur Schopenhauer