SELECT str AS result

FROM expln('

SELECT x FROM A where x < 10 group by(x);') AS str

WHERE str NOT LIKE 'Query Identifier%';

WHERE str NOT LIKE 'Query Identifier%' and str NOT LIKE '%Memory%';

result

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

HashAggregate (actual rows=10 loops=1)

AQO not used

Output: x

Group Key: a.x

Batches: 1 Memory Usage: 40kB

-> Seq Scan on public.a (actual rows=1000 loops=1)

AQO not used

Output: x

Filter: (a.x < 10)

Using aqo: true

AQO mode: LEARN

JOINS: 0

(12 rows)

(11 rows)

-- cardinality 1000 in Seq Scan on a

SELECT str AS result

FROM expln('

SELECT x,y FROM A,B WHERE x < 10 AND A.x = B.y;') AS str

WHERE str NOT LIKE 'Query Identifier%';

WHERE str NOT LIKE 'Query Identifier%' and str NOT LIKE '%Memory%';

result

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

Merge Join (actual rows=100000 loops=1)

AQO not used

Output: a.x

Sort Key: a.x

Sort Method: quicksort Memory: 79kB

-> Seq Scan on public.a (actual rows=1000 loops=1)

AQO: rows=1000, error=0%

Output: a.x

AQO not used

Output: b.y

Sort Key: b.y

Sort Method: quicksort Memory: 79kB

-> Seq Scan on public.b (actual rows=1000 loops=1)

AQO not used

Output: b.y

Using aqo: true

AQO mode: LEARN

JOINS: 0

(24 rows)

(22 rows)

-- cardinality 100 in Seq Scan on a and Seq Scan on b

SELECT str AS result

FROM expln('

SELECT x FROM A,B where x < 10 and y > 10 group by(x);') AS str

WHERE str NOT LIKE 'Query Identifier%';

WHERE str NOT LIKE 'Query Identifier%' and str NOT LIKE '%Memory%';

result

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

HashAggregate (actual rows=0 loops=1)

AQO not used

Output: a.x

Group Key: a.x

Batches: 1 Memory Usage: 40kB

-> Nested Loop (actual rows=0 loops=1)

AQO not used

Output: a.x

Using aqo: true

AQO mode: LEARN

JOINS: 1

(21 rows)

(20 rows)

-- cardinality 1000 Hash Cond: (a.x = b.y) and 1 Seq Scan on b

-- this cardinality is wrong because we take it from bad neibours (previous query).

-- clause y > 10 give count of rows with the same clauses.

SELECT str AS result

FROM expln('

SELECT x,y FROM A,B WHERE x < 10 and y > 10 AND A.x = B.y;') AS str

WHERE str NOT LIKE 'Query Identifier%';

WHERE str NOT LIKE 'Query Identifier%' and str NOT LIKE '%Memory%';

result

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

Hash Join (actual rows=0 loops=1)

-> Hash (actual rows=0 loops=1)

AQO not used

Output: b.y

Buckets: 1024 Batches: 1 Memory Usage: 8kB

-> Seq Scan on public.b (actual rows=0 loops=1)

AQO: rows=1, error=100%

Output: b.y

Using aqo: true

AQO mode: LEARN

JOINS: 0

(20 rows)

(19 rows)

DROP EXTENSION aqo CASCADE;

SELECT strAS result

FROM expln('

SELECT x FROM A where x < 10 group by(x);')AS str

WHERE str NOTLIKE'Query Identifier%';

WHERE str NOTLIKE'Query Identifier%'and str NOTLIKE'%Memory%';

SELECT strAS result

FROM expln('

SELECT x,y FROM A,B WHERE x < 10 AND A.x = B.y;')AS str

WHERE str NOTLIKE'Query Identifier%';

WHERE str NOTLIKE'Query Identifier%'and str NOTLIKE'%Memory%';

SELECT strAS result

FROM expln('

SELECT x FROM A,B where x < 10 and y > 10 group by(x);')AS str

WHERE str NOTLIKE'Query Identifier%';

WHERE str NOTLIKE'Query Identifier%'and str NOTLIKE'%Memory%';

SELECT strAS result

FROM expln('

SELECT x,y FROM A,B WHERE x < 10 and y > 10 AND A.x = B.y;')AS str

WHERE str NOTLIKE'Query Identifier%';

WHERE str NOTLIKE'Query Identifier%'and str NOTLIKE'%Memory%';

DROP EXTENSION aqo CASCADE;