Re: [HACKERS] Partition-wise aggregation/grouping - Mailing list pgsql-hackers

On Thu, Dec 14, 2017 at 4:01 PM, Ashutosh Bapat <ashutosh.bapat@enterprisedb.com> wrote:

+
+-- Partial aggregation as GROUP BY clause does not match with PARTITION KEY
+EXPLAIN (COSTS OFF)
+SELECT b, sum(a), count(*) FROM pagg_tab GROUP BY b ORDER BY 1, 2, 3;
+                           QUERY PLAN
+----------------------------------------------------------------
+ Sort
+   Sort Key: pagg_tab_p1.b, (sum(pagg_tab_p1.a)), (count(*))
+   ->  Finalize GroupAggregate
+         Group Key: pagg_tab_p1.b
+         ->  Sort
+               Sort Key: pagg_tab_p1.b
+               ->  Append
+                     ->  Partial HashAggregate
+                           Group Key: pagg_tab_p1.b
+                           ->  Seq Scan on pagg_tab_p1
+                     ->  Partial HashAggregate
+                           Group Key: pagg_tab_p2_s1.b
+                           ->  Append
+                                 ->  Seq Scan on pagg_tab_p2_s1
+                                 ->  Seq Scan on pagg_tab_p2_s2
+                     ->  Partial HashAggregate
+                           Group Key: pagg_tab_p3_s1.b
+                           ->  Append
+                                 ->  Seq Scan on pagg_tab_p3_s1
+                                 ->  Seq Scan on pagg_tab_p3_s2
+(20 rows)

Why aren't we seeing partial aggregation paths for level two and below
partitions?

In this version of the patch I have not recursed into next level.

Will work on it and submit changes in the next patch-set.