Re: Aggregate leads to superfluous projection from the scan - Mailing list pgsql-hackers

Hi,

Here is the query which involves aggregate on a single column:

https://dbfiddle.uk/?rdbms=postgres_13&fiddle=44bfd8f6b6b5aad34d00d449c04c5a96

As you can see from `Output:`, there are many columns added which are not needed by the query executor.

I wonder if someone has noticed this in the past.

If so, what was the discussion around this topic ?

Thanks

                                                              QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------
 Aggregate  (cost=119.00..119.01 rows=1 width=8) (actual time=9.453..9.453 rows=1 loops=1)
   Output: count(fire_year)
   ->  Index Scan using fires_pkey on public.fires t  (cost=0.00..116.50 rows=1000 width=4) (actual time=9.432..9.432 rows=0 loops=1)
         Output: fire_year
         Index Cond: (t.objectid <= 2000000)
 Planning Time: 52.598 ms
 Execution Time: 13.082 ms

Please pay attention to the column list after `Output:`

Tom:

Can you take a look and let me know what I may have missed ?

Thanks