EXPLAIN and nfiltered

Hi,

Here's a patch for showing in EXPLAIN ANALYZE the number of rows a plan 
qual filtered from a node's input.  The output looks like this:


                                                       QUERY PLAN 

-----------------------------------------------------------------------------------------------------------------------
  Subquery Scan on ss  (cost=0.00..50.00 rows=267 width=4) (actual 
time=0.035..0.088 rows=5 filtered=3 loops=1)
    Filter: (ss.a < 6)
    ->  Limit  (cost=0.00..40.00 rows=800 width=4) (actual 
time=0.031..0.067 rows=8 filtered=0 loops=1)
          ->  Seq Scan on foo  (cost=0.00..40.00 rows=800 width=4) 
(actual time=0.027..0.040 rows=8 filtered=2 loops=1)
                Filter: (a < 9)
  Total runtime: 0.146 ms
(6 rows)


It might be better if the output was on the Filter: line but this was 
just the result of a quick idea and I wanted to see how much work the 
actual implementation would be.

Any suggestions and comments on the output format, the patch and the 
idea are welcome.


Regards,
Marko Tiikkaja