-- e.g. due to an index scan.

BEGIN;

SET LOCAL enable_hashagg = false;

EXPLAIN SELECT a, b, count(*), max(a), max(b) FROM gstest3 GROUP BY GROUPING SETS(a, b,()) ORDER BY a, b;

QUERY PLAN

-------------------------------------------------------------------------

Sort (cost=1.20..1.21 rows=5 width=24)

EXPLAIN(COSTS OFF)SELECT a, b, count(*), max(a), max(b) FROM gstest3 GROUP BY GROUPING SETS(a, b,()) ORDER BY a, b;

QUERY PLAN

---------------------------------------

Sort

Sort Key: a, b

-> GroupAggregate (cost=1.03..1.14 rows=5 width=24)

-> GroupAggregate

Group Key: a

Group Key: ()

Sort Key: b

Group Key: b

-> Sort (cost=1.03..1.03 rows=2 width=8)

-> Sort

Sort Key: a

-> Seq Scan on gstest3 (cost=0.00..1.02 rows=2 width=8)

-> Seq Scan on gstest3

(10 rows)

SELECT a, b, count(*), max(a), max(b) FROM gstest3 GROUP BY GROUPING SETS(a, b,()) ORDER BY a, b;

(5 rows)

SET LOCAL enable_seqscan = false;

EXPLAIN SELECT a, b, count(*), max(a), max(b) FROM gstest3 GROUP BY GROUPING SETS(a, b,()) ORDER BY a, b;

QUERY PLAN

-----------------------------------------------------------------------------------------

Sort (cost=12.32..12.33 rows=5 width=24)

EXPLAIN(COSTS OFF)SELECT a, b, count(*), max(a), max(b) FROM gstest3 GROUP BY GROUPING SETS(a, b,()) ORDER BY a, b;

QUERY PLAN

------------------------------------------------------

Sort

Sort Key: a, b

-> GroupAggregate (cost=0.13..12.26 rows=5 width=24)

-> GroupAggregate

Group Key: a

Group Key: ()

Sort Key: b

Group Key: b

-> Index Scan using gstest3_pkey on gstest3 (cost=0.13..12.16 rows=2 width=8)

-> Index Scan using gstest3_pkey on gstest3

(8 rows)

SELECT a, b, count(*), max(a), max(b) FROM gstest3 GROUP BY GROUPING SETS(a, b,()) ORDER BY a, b;

BEGIN;

SET LOCAL enable_hashagg= false;

EXPLAINSELECT a, b,count(*),max(a),max(b)FROM gstest3GROUP BY GROUPING SETS(a, b,())ORDER BY a, b;

EXPLAIN(COSTS OFF)SELECT a, b,count(*),max(a),max(b)FROM gstest3GROUP BY GROUPING SETS(a, b,())ORDER BY a, b;

SELECT a, b,count(*),max(a),max(b)FROM gstest3GROUP BY GROUPING SETS(a, b,())ORDER BY a, b;

SET LOCAL enable_seqscan= false;

EXPLAINSELECT a, b,count(*),max(a),max(b)FROM gstest3GROUP BY GROUPING SETS(a, b,())ORDER BY a, b;

EXPLAIN(COSTS OFF)SELECT a, b,count(*),max(a),max(b)FROM gstest3GROUP BY GROUPING SETS(a, b,())ORDER BY a, b;

SELECT a, b,count(*),max(a),max(b)FROM gstest3GROUP BY GROUPING SETS(a, b,())ORDER BY a, b;

COMMIT;