postgresql/src/test/regress/expected/union.out

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2000-01-06 07:40:54 +01:00
--
-- UNION (also INTERSECT, EXCEPT)
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--
-- Simple UNION constructs
SELECT 1 AS two UNION SELECT 2 ORDER BY 1;
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two
-----
1
2
(2 rows)
SELECT 1 AS one UNION SELECT 1 ORDER BY 1;
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one
-----
1
(1 row)
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SELECT 1 AS two UNION ALL SELECT 2;
two
-----
1
2
(2 rows)
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SELECT 1 AS two UNION ALL SELECT 1;
two
-----
1
1
(2 rows)
SELECT 1 AS three UNION SELECT 2 UNION SELECT 3 ORDER BY 1;
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three
-------
1
2
3
(3 rows)
SELECT 1 AS two UNION SELECT 2 UNION SELECT 2 ORDER BY 1;
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two
-----
1
2
(2 rows)
SELECT 1 AS three UNION SELECT 2 UNION ALL SELECT 2 ORDER BY 1;
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three
-------
1
2
2
(3 rows)
SELECT 1.1 AS two UNION SELECT 2.2 ORDER BY 1;
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two
-----
1.1
2.2
(2 rows)
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-- Mixed types
SELECT 1.1 AS two UNION SELECT 2 ORDER BY 1;
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two
-----
1.1
2
(2 rows)
SELECT 1 AS two UNION SELECT 2.2 ORDER BY 1;
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two
-----
1
2.2
(2 rows)
SELECT 1 AS one UNION SELECT 1.0::float8 ORDER BY 1;
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one
-----
1
(1 row)
SELECT 1.1 AS two UNION ALL SELECT 2 ORDER BY 1;
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two
-----
1.1
2
(2 rows)
SELECT 1.0::float8 AS two UNION ALL SELECT 1 ORDER BY 1;
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two
-----
1
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1
(2 rows)
SELECT 1.1 AS three UNION SELECT 2 UNION SELECT 3 ORDER BY 1;
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three
-------
1.1
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2
3
(3 rows)
SELECT 1.1::float8 AS two UNION SELECT 2 UNION SELECT 2.0::float8 ORDER BY 1;
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two
-----
1.1
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2
(2 rows)
SELECT 1.1 AS three UNION SELECT 2 UNION ALL SELECT 2 ORDER BY 1;
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three
-------
1.1
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2
2
(3 rows)
SELECT 1.1 AS two UNION (SELECT 2 UNION ALL SELECT 2) ORDER BY 1;
two
-----
1.1
2
(2 rows)
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--
-- Try testing from tables...
--
SELECT f1 AS five FROM FLOAT8_TBL
UNION
SELECT f1 FROM FLOAT8_TBL
ORDER BY 1;
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five
-----------------------
-1.2345678901234e+200
-1004.3
-34.84
-1.2345678901234e-200
0
(5 rows)
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SELECT f1 AS ten FROM FLOAT8_TBL
UNION ALL
SELECT f1 FROM FLOAT8_TBL;
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ten
-----------------------
0
-34.84
-1004.3
-1.2345678901234e+200
-1.2345678901234e-200
0
-34.84
-1004.3
-1.2345678901234e+200
-1.2345678901234e-200
(10 rows)
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SELECT f1 AS nine FROM FLOAT8_TBL
UNION
SELECT f1 FROM INT4_TBL
ORDER BY 1;
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nine
-----------------------
-1.2345678901234e+200
-2147483647
-123456
-1004.3
-34.84
-1.2345678901234e-200
0
123456
2147483647
(9 rows)
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SELECT f1 AS ten FROM FLOAT8_TBL
UNION ALL
SELECT f1 FROM INT4_TBL;
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ten
-----------------------
0
-34.84
-1004.3
-1.2345678901234e+200
-1.2345678901234e-200
0
123456
-123456
2147483647
-2147483647
(10 rows)
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SELECT f1 AS five FROM FLOAT8_TBL
WHERE f1 BETWEEN -1e6 AND 1e6
UNION
SELECT f1 FROM INT4_TBL
WHERE f1 BETWEEN 0 AND 1000000
ORDER BY 1;
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five
-----------------------
-1004.3
-34.84
-1.2345678901234e-200
0
123456
(5 rows)
SELECT CAST(f1 AS char(4)) AS three FROM VARCHAR_TBL
UNION
SELECT f1 FROM CHAR_TBL
ORDER BY 1;
three
-------
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a
ab
abcd
(3 rows)
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SELECT f1 AS three FROM VARCHAR_TBL
UNION
SELECT CAST(f1 AS varchar) FROM CHAR_TBL
ORDER BY 1;
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three
-------
a
ab
abcd
(3 rows)
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SELECT f1 AS eight FROM VARCHAR_TBL
UNION ALL
SELECT f1 FROM CHAR_TBL;
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eight
-------
a
ab
abcd
abcd
a
ab
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abcd
abcd
(8 rows)
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SELECT f1 AS five FROM TEXT_TBL
UNION
SELECT f1 FROM VARCHAR_TBL
UNION
SELECT TRIM(TRAILING FROM f1) FROM CHAR_TBL
ORDER BY 1;
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five
-------------------
a
ab
abcd
doh!
hi de ho neighbor
(5 rows)
--
-- INTERSECT and EXCEPT
--
SELECT q2 FROM int8_tbl INTERSECT SELECT q1 FROM int8_tbl ORDER BY 1;
q2
------------------
123
4567890123456789
(2 rows)
SELECT q2 FROM int8_tbl INTERSECT ALL SELECT q1 FROM int8_tbl ORDER BY 1;
q2
------------------
123
4567890123456789
4567890123456789
(3 rows)
SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl ORDER BY 1;
q2
-------------------
-4567890123456789
456
(2 rows)
SELECT q2 FROM int8_tbl EXCEPT ALL SELECT q1 FROM int8_tbl ORDER BY 1;
q2
-------------------
-4567890123456789
456
(2 rows)
SELECT q2 FROM int8_tbl EXCEPT ALL SELECT DISTINCT q1 FROM int8_tbl ORDER BY 1;
q2
-------------------
-4567890123456789
456
4567890123456789
(3 rows)
SELECT q1 FROM int8_tbl EXCEPT SELECT q2 FROM int8_tbl ORDER BY 1;
q1
----
(0 rows)
SELECT q1 FROM int8_tbl EXCEPT ALL SELECT q2 FROM int8_tbl ORDER BY 1;
q1
------------------
123
4567890123456789
(2 rows)
SELECT q1 FROM int8_tbl EXCEPT ALL SELECT DISTINCT q2 FROM int8_tbl ORDER BY 1;
q1
------------------
123
4567890123456789
4567890123456789
(3 rows)
SELECT q1 FROM int8_tbl EXCEPT ALL SELECT q1 FROM int8_tbl FOR NO KEY UPDATE;
ERROR: FOR NO KEY UPDATE is not allowed with UNION/INTERSECT/EXCEPT
-- nested cases
(SELECT 1,2,3 UNION SELECT 4,5,6) INTERSECT SELECT 4,5,6;
?column? | ?column? | ?column?
----------+----------+----------
4 | 5 | 6
(1 row)
(SELECT 1,2,3 UNION SELECT 4,5,6 ORDER BY 1,2) INTERSECT SELECT 4,5,6;
?column? | ?column? | ?column?
----------+----------+----------
4 | 5 | 6
(1 row)
(SELECT 1,2,3 UNION SELECT 4,5,6) EXCEPT SELECT 4,5,6;
?column? | ?column? | ?column?
----------+----------+----------
1 | 2 | 3
(1 row)
(SELECT 1,2,3 UNION SELECT 4,5,6 ORDER BY 1,2) EXCEPT SELECT 4,5,6;
?column? | ?column? | ?column?
----------+----------+----------
1 | 2 | 3
(1 row)
-- exercise both hashed and sorted implementations of UNION/INTERSECT/EXCEPT
set enable_hashagg to on;
explain (costs off)
select count(*) from
( select unique1 from tenk1 union select fivethous from tenk1 ) ss;
QUERY PLAN
----------------------------------------------------------------
Aggregate
-> HashAggregate
Group Key: tenk1.unique1
-> Append
-> Index Only Scan using tenk1_unique1 on tenk1
-> Seq Scan on tenk1 tenk1_1
(6 rows)
select count(*) from
( select unique1 from tenk1 union select fivethous from tenk1 ) ss;
count
-------
10000
(1 row)
explain (costs off)
select count(*) from
( select unique1 from tenk1 intersect select fivethous from tenk1 ) ss;
QUERY PLAN
------------------------------------------------------------------------------------
Aggregate
-> Subquery Scan on ss
-> HashSetOp Intersect
-> Append
-> Subquery Scan on "*SELECT* 2"
-> Seq Scan on tenk1
-> Subquery Scan on "*SELECT* 1"
-> Index Only Scan using tenk1_unique1 on tenk1 tenk1_1
(8 rows)
select count(*) from
( select unique1 from tenk1 intersect select fivethous from tenk1 ) ss;
count
-------
5000
(1 row)
explain (costs off)
select unique1 from tenk1 except select unique2 from tenk1 where unique2 != 10;
QUERY PLAN
------------------------------------------------------------------------
HashSetOp Except
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Index Only Scan using tenk1_unique1 on tenk1
-> Subquery Scan on "*SELECT* 2"
-> Index Only Scan using tenk1_unique2 on tenk1 tenk1_1
Filter: (unique2 <> 10)
(7 rows)
select unique1 from tenk1 except select unique2 from tenk1 where unique2 != 10;
unique1
---------
10
(1 row)
set enable_hashagg to off;
explain (costs off)
select count(*) from
( select unique1 from tenk1 union select fivethous from tenk1 ) ss;
QUERY PLAN
----------------------------------------------------------------
Aggregate
-> Unique
-> Merge Append
Sort Key: tenk1.unique1
-> Index Only Scan using tenk1_unique1 on tenk1
-> Sort
Sort Key: tenk1_1.fivethous
-> Seq Scan on tenk1 tenk1_1
(8 rows)
select count(*) from
( select unique1 from tenk1 union select fivethous from tenk1 ) ss;
count
-------
10000
(1 row)
explain (costs off)
select count(*) from
( select unique1 from tenk1 intersect select fivethous from tenk1 ) ss;
QUERY PLAN
------------------------------------------------------------------------------------------
Aggregate
-> Subquery Scan on ss
-> SetOp Intersect
-> Sort
Sort Key: "*SELECT* 2".fivethous
-> Append
-> Subquery Scan on "*SELECT* 2"
-> Seq Scan on tenk1
-> Subquery Scan on "*SELECT* 1"
-> Index Only Scan using tenk1_unique1 on tenk1 tenk1_1
(10 rows)
select count(*) from
( select unique1 from tenk1 intersect select fivethous from tenk1 ) ss;
count
-------
5000
(1 row)
explain (costs off)
select unique1 from tenk1 except select unique2 from tenk1 where unique2 != 10;
QUERY PLAN
------------------------------------------------------------------------------
SetOp Except
-> Sort
Sort Key: "*SELECT* 1".unique1
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Index Only Scan using tenk1_unique1 on tenk1
-> Subquery Scan on "*SELECT* 2"
-> Index Only Scan using tenk1_unique2 on tenk1 tenk1_1
Filter: (unique2 <> 10)
(9 rows)
select unique1 from tenk1 except select unique2 from tenk1 where unique2 != 10;
unique1
---------
10
(1 row)
reset enable_hashagg;
-- non-hashable type
set enable_hashagg to on;
explain (costs off)
select x from (values ('11'::varbit), ('10'::varbit)) _(x) union select x from (values ('11'::varbit), ('10'::varbit)) _(x);
QUERY PLAN
-----------------------------------------------
Unique
-> Sort
Sort Key: "*VALUES*".column1
-> Append
-> Values Scan on "*VALUES*"
-> Values Scan on "*VALUES*_1"
(6 rows)
set enable_hashagg to off;
explain (costs off)
select x from (values ('11'::varbit), ('10'::varbit)) _(x) union select x from (values ('11'::varbit), ('10'::varbit)) _(x);
QUERY PLAN
-----------------------------------------------
Unique
-> Sort
Sort Key: "*VALUES*".column1
-> Append
-> Values Scan on "*VALUES*"
-> Values Scan on "*VALUES*_1"
(6 rows)
reset enable_hashagg;
-- arrays
set enable_hashagg to on;
explain (costs off)
select x from (values (array[1, 2]), (array[1, 3])) _(x) union select x from (values (array[1, 2]), (array[1, 4])) _(x);
QUERY PLAN
-----------------------------------------
HashAggregate
Group Key: "*VALUES*".column1
-> Append
-> Values Scan on "*VALUES*"
-> Values Scan on "*VALUES*_1"
(5 rows)
select x from (values (array[1, 2]), (array[1, 3])) _(x) union select x from (values (array[1, 2]), (array[1, 4])) _(x);
x
-------
{1,4}
{1,2}
{1,3}
(3 rows)
explain (costs off)
select x from (values (array[1, 2]), (array[1, 3])) _(x) intersect select x from (values (array[1, 2]), (array[1, 4])) _(x);
QUERY PLAN
-----------------------------------------------
HashSetOp Intersect
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Values Scan on "*VALUES*"
-> Subquery Scan on "*SELECT* 2"
-> Values Scan on "*VALUES*_1"
(6 rows)
select x from (values (array[1, 2]), (array[1, 3])) _(x) intersect select x from (values (array[1, 2]), (array[1, 4])) _(x);
x
-------
{1,2}
(1 row)
explain (costs off)
select x from (values (array[1, 2]), (array[1, 3])) _(x) except select x from (values (array[1, 2]), (array[1, 4])) _(x);
QUERY PLAN
-----------------------------------------------
HashSetOp Except
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Values Scan on "*VALUES*"
-> Subquery Scan on "*SELECT* 2"
-> Values Scan on "*VALUES*_1"
(6 rows)
select x from (values (array[1, 2]), (array[1, 3])) _(x) except select x from (values (array[1, 2]), (array[1, 4])) _(x);
x
-------
{1,3}
(1 row)
-- non-hashable type
explain (costs off)
select x from (values (array['10'::varbit]), (array['11'::varbit])) _(x) union select x from (values (array['10'::varbit]), (array['01'::varbit])) _(x);
QUERY PLAN
-----------------------------------------------
Unique
-> Sort
Sort Key: "*VALUES*".column1
-> Append
-> Values Scan on "*VALUES*"
-> Values Scan on "*VALUES*_1"
(6 rows)
select x from (values (array['10'::varbit]), (array['11'::varbit])) _(x) union select x from (values (array['10'::varbit]), (array['01'::varbit])) _(x);
x
------
{01}
{10}
{11}
(3 rows)
set enable_hashagg to off;
explain (costs off)
select x from (values (array[1, 2]), (array[1, 3])) _(x) union select x from (values (array[1, 2]), (array[1, 4])) _(x);
QUERY PLAN
-----------------------------------------------
Unique
-> Sort
Sort Key: "*VALUES*".column1
-> Append
-> Values Scan on "*VALUES*"
-> Values Scan on "*VALUES*_1"
(6 rows)
select x from (values (array[1, 2]), (array[1, 3])) _(x) union select x from (values (array[1, 2]), (array[1, 4])) _(x);
x
-------
{1,2}
{1,3}
{1,4}
(3 rows)
explain (costs off)
select x from (values (array[1, 2]), (array[1, 3])) _(x) intersect select x from (values (array[1, 2]), (array[1, 4])) _(x);
QUERY PLAN
-----------------------------------------------------
SetOp Intersect
-> Sort
Sort Key: "*SELECT* 1".x
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Values Scan on "*VALUES*"
-> Subquery Scan on "*SELECT* 2"
-> Values Scan on "*VALUES*_1"
(8 rows)
select x from (values (array[1, 2]), (array[1, 3])) _(x) intersect select x from (values (array[1, 2]), (array[1, 4])) _(x);
x
-------
{1,2}
(1 row)
explain (costs off)
select x from (values (array[1, 2]), (array[1, 3])) _(x) except select x from (values (array[1, 2]), (array[1, 4])) _(x);
QUERY PLAN
-----------------------------------------------------
SetOp Except
-> Sort
Sort Key: "*SELECT* 1".x
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Values Scan on "*VALUES*"
-> Subquery Scan on "*SELECT* 2"
-> Values Scan on "*VALUES*_1"
(8 rows)
select x from (values (array[1, 2]), (array[1, 3])) _(x) except select x from (values (array[1, 2]), (array[1, 4])) _(x);
x
-------
{1,3}
(1 row)
reset enable_hashagg;
-- records
set enable_hashagg to on;
explain (costs off)
select x from (values (row(1, 2)), (row(1, 3))) _(x) union select x from (values (row(1, 2)), (row(1, 4))) _(x);
QUERY PLAN
-----------------------------------------------
Unique
-> Sort
Sort Key: "*VALUES*".column1
-> Append
-> Values Scan on "*VALUES*"
-> Values Scan on "*VALUES*_1"
(6 rows)
select x from (values (row(1, 2)), (row(1, 3))) _(x) union select x from (values (row(1, 2)), (row(1, 4))) _(x);
x
-------
(1,2)
(1,3)
(1,4)
(3 rows)
explain (costs off)
select x from (values (row(1, 2)), (row(1, 3))) _(x) intersect select x from (values (row(1, 2)), (row(1, 4))) _(x);
QUERY PLAN
-----------------------------------------------------
SetOp Intersect
-> Sort
Sort Key: "*SELECT* 1".x
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Values Scan on "*VALUES*"
-> Subquery Scan on "*SELECT* 2"
-> Values Scan on "*VALUES*_1"
(8 rows)
select x from (values (row(1, 2)), (row(1, 3))) _(x) intersect select x from (values (row(1, 2)), (row(1, 4))) _(x);
x
-------
(1,2)
(1 row)
explain (costs off)
select x from (values (row(1, 2)), (row(1, 3))) _(x) except select x from (values (row(1, 2)), (row(1, 4))) _(x);
QUERY PLAN
-----------------------------------------------------
SetOp Except
-> Sort
Sort Key: "*SELECT* 1".x
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Values Scan on "*VALUES*"
-> Subquery Scan on "*SELECT* 2"
-> Values Scan on "*VALUES*_1"
(8 rows)
select x from (values (row(1, 2)), (row(1, 3))) _(x) except select x from (values (row(1, 2)), (row(1, 4))) _(x);
x
-------
(1,3)
(1 row)
-- non-hashable type
-- With an anonymous row type, the typcache does not report that the
-- type is hashable. (Otherwise, this would fail at execution time.)
explain (costs off)
select x from (values (row('10'::varbit)), (row('11'::varbit))) _(x) union select x from (values (row('10'::varbit)), (row('01'::varbit))) _(x);
QUERY PLAN
-----------------------------------------------
Unique
-> Sort
Sort Key: "*VALUES*".column1
-> Append
-> Values Scan on "*VALUES*"
-> Values Scan on "*VALUES*_1"
(6 rows)
select x from (values (row('10'::varbit)), (row('11'::varbit))) _(x) union select x from (values (row('10'::varbit)), (row('01'::varbit))) _(x);
x
------
(01)
(10)
(11)
(3 rows)
-- With a defined row type, the typcache can inspect the type's fields
-- for hashability.
create type ct1 as (f1 varbit);
explain (costs off)
select x from (values (row('10'::varbit)::ct1), (row('11'::varbit)::ct1)) _(x) union select x from (values (row('10'::varbit)::ct1), (row('01'::varbit)::ct1)) _(x);
QUERY PLAN
-----------------------------------------------
Unique
-> Sort
Sort Key: "*VALUES*".column1
-> Append
-> Values Scan on "*VALUES*"
-> Values Scan on "*VALUES*_1"
(6 rows)
select x from (values (row('10'::varbit)::ct1), (row('11'::varbit)::ct1)) _(x) union select x from (values (row('10'::varbit)::ct1), (row('01'::varbit)::ct1)) _(x);
x
------
(01)
(10)
(11)
(3 rows)
drop type ct1;
set enable_hashagg to off;
explain (costs off)
select x from (values (row(1, 2)), (row(1, 3))) _(x) union select x from (values (row(1, 2)), (row(1, 4))) _(x);
QUERY PLAN
-----------------------------------------------
Unique
-> Sort
Sort Key: "*VALUES*".column1
-> Append
-> Values Scan on "*VALUES*"
-> Values Scan on "*VALUES*_1"
(6 rows)
select x from (values (row(1, 2)), (row(1, 3))) _(x) union select x from (values (row(1, 2)), (row(1, 4))) _(x);
x
-------
(1,2)
(1,3)
(1,4)
(3 rows)
explain (costs off)
select x from (values (row(1, 2)), (row(1, 3))) _(x) intersect select x from (values (row(1, 2)), (row(1, 4))) _(x);
QUERY PLAN
-----------------------------------------------------
SetOp Intersect
-> Sort
Sort Key: "*SELECT* 1".x
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Values Scan on "*VALUES*"
-> Subquery Scan on "*SELECT* 2"
-> Values Scan on "*VALUES*_1"
(8 rows)
select x from (values (row(1, 2)), (row(1, 3))) _(x) intersect select x from (values (row(1, 2)), (row(1, 4))) _(x);
x
-------
(1,2)
(1 row)
explain (costs off)
select x from (values (row(1, 2)), (row(1, 3))) _(x) except select x from (values (row(1, 2)), (row(1, 4))) _(x);
QUERY PLAN
-----------------------------------------------------
SetOp Except
-> Sort
Sort Key: "*SELECT* 1".x
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Values Scan on "*VALUES*"
-> Subquery Scan on "*SELECT* 2"
-> Values Scan on "*VALUES*_1"
(8 rows)
select x from (values (row(1, 2)), (row(1, 3))) _(x) except select x from (values (row(1, 2)), (row(1, 4))) _(x);
x
-------
(1,3)
(1 row)
reset enable_hashagg;
--
-- Mixed types
--
SELECT f1 FROM float8_tbl INTERSECT SELECT f1 FROM int4_tbl ORDER BY 1;
f1
----
0
(1 row)
SELECT f1 FROM float8_tbl EXCEPT SELECT f1 FROM int4_tbl ORDER BY 1;
f1
-----------------------
-1.2345678901234e+200
-1004.3
-34.84
-1.2345678901234e-200
(4 rows)
--
-- Operator precedence and (((((extra))))) parentheses
--
SELECT q1 FROM int8_tbl INTERSECT SELECT q2 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl ORDER BY 1;
q1
-------------------
-4567890123456789
123
123
456
4567890123456789
4567890123456789
4567890123456789
(7 rows)
SELECT q1 FROM int8_tbl INTERSECT (((SELECT q2 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl))) ORDER BY 1;
q1
------------------
123
4567890123456789
(2 rows)
(((SELECT q1 FROM int8_tbl INTERSECT SELECT q2 FROM int8_tbl ORDER BY 1))) UNION ALL SELECT q2 FROM int8_tbl;
q1
-------------------
123
4567890123456789
456
4567890123456789
123
4567890123456789
-4567890123456789
(7 rows)
SELECT q1 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl ORDER BY 1;
q1
-------------------
-4567890123456789
456
(2 rows)
SELECT q1 FROM int8_tbl UNION ALL (((SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl ORDER BY 1)));
q1
-------------------
123
123
4567890123456789
4567890123456789
4567890123456789
-4567890123456789
456
(7 rows)
(((SELECT q1 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl))) EXCEPT SELECT q1 FROM int8_tbl ORDER BY 1;
q1
-------------------
-4567890123456789
456
(2 rows)
--
-- Subqueries with ORDER BY & LIMIT clauses
--
-- In this syntax, ORDER BY/LIMIT apply to the result of the EXCEPT
SELECT q1,q2 FROM int8_tbl EXCEPT SELECT q2,q1 FROM int8_tbl
ORDER BY q2,q1;
q1 | q2
------------------+-------------------
4567890123456789 | -4567890123456789
123 | 456
(2 rows)
-- This should fail, because q2 isn't a name of an EXCEPT output column
SELECT q1 FROM int8_tbl EXCEPT SELECT q2 FROM int8_tbl ORDER BY q2 LIMIT 1;
ERROR: column "q2" does not exist
LINE 1: ... int8_tbl EXCEPT SELECT q2 FROM int8_tbl ORDER BY q2 LIMIT 1...
^
DETAIL: There is a column named "q2" in table "*SELECT* 2", but it cannot be referenced from this part of the query.
-- But this should work:
SELECT q1 FROM int8_tbl EXCEPT (((SELECT q2 FROM int8_tbl ORDER BY q2 LIMIT 1))) ORDER BY 1;
q1
------------------
123
4567890123456789
(2 rows)
--
-- New syntaxes (7.1) permit new tests
--
(((((select * from int8_tbl)))));
q1 | q2
------------------+-------------------
123 | 456
123 | 4567890123456789
4567890123456789 | 123
4567890123456789 | 4567890123456789
4567890123456789 | -4567890123456789
(5 rows)
--
-- Check behavior with empty select list (allowed since 9.4)
--
select union select;
--
(1 row)
select intersect select;
--
(1 row)
select except select;
--
(0 rows)
-- check hashed implementation
set enable_hashagg = true;
set enable_sort = false;
-- We've no way to check hashed UNION as the empty pathkeys in the Append are
-- fine to make use of Unique, which is cheaper than HashAggregate and we've
-- no means to disable Unique.
explain (costs off)
select from generate_series(1,5) intersect select from generate_series(1,3);
QUERY PLAN
----------------------------------------------------------------------
HashSetOp Intersect
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Function Scan on generate_series
-> Subquery Scan on "*SELECT* 2"
-> Function Scan on generate_series generate_series_1
(6 rows)
select from generate_series(1,5) union all select from generate_series(1,3);
--
(8 rows)
select from generate_series(1,5) intersect select from generate_series(1,3);
--
(1 row)
select from generate_series(1,5) intersect all select from generate_series(1,3);
--
(3 rows)
select from generate_series(1,5) except select from generate_series(1,3);
--
(0 rows)
select from generate_series(1,5) except all select from generate_series(1,3);
--
(2 rows)
-- check sorted implementation
set enable_hashagg = false;
set enable_sort = true;
explain (costs off)
select from generate_series(1,5) union select from generate_series(1,3);
QUERY PLAN
----------------------------------------------------------------
Unique
-> Append
-> Function Scan on generate_series
-> Function Scan on generate_series generate_series_1
(4 rows)
explain (costs off)
select from generate_series(1,5) intersect select from generate_series(1,3);
QUERY PLAN
----------------------------------------------------------------------
SetOp Intersect
-> Append
-> Subquery Scan on "*SELECT* 1"
-> Function Scan on generate_series
-> Subquery Scan on "*SELECT* 2"
-> Function Scan on generate_series generate_series_1
(6 rows)
select from generate_series(1,5) union select from generate_series(1,3);
--
(1 row)
select from generate_series(1,5) union all select from generate_series(1,3);
--
(8 rows)
select from generate_series(1,5) intersect select from generate_series(1,3);
--
(1 row)
select from generate_series(1,5) intersect all select from generate_series(1,3);
--
(3 rows)
select from generate_series(1,5) except select from generate_series(1,3);
--
(0 rows)
select from generate_series(1,5) except all select from generate_series(1,3);
--
(2 rows)
-- Try a variation of the above but with a CTE which contains a column, again
-- with an empty final select list.
-- Ensure we get the expected 1 row with 0 columns
with cte as materialized (select s from generate_series(1,5) s)
select from cte union select from cte;
--
(1 row)
-- Ensure we get the same result as the above.
with cte as not materialized (select s from generate_series(1,5) s)
select from cte union select from cte;
--
(1 row)
reset enable_hashagg;
reset enable_sort;
--
-- Check handling of a case with unknown constants. We don't guarantee
-- an undecorated constant will work in all cases, but historically this
-- usage has worked, so test we don't break it.
--
SELECT a.f1 FROM (SELECT 'test' AS f1 FROM varchar_tbl) a
UNION
SELECT b.f1 FROM (SELECT f1 FROM varchar_tbl) b
ORDER BY 1;
f1
------
a
ab
abcd
test
(4 rows)
-- This should fail, but it should produce an error cursor
SELECT '3.4'::numeric UNION SELECT 'foo';
ERROR: invalid input syntax for type numeric: "foo"
LINE 1: SELECT '3.4'::numeric UNION SELECT 'foo';
^
--
-- Test that expression-index constraints can be pushed down through
-- UNION or UNION ALL
--
CREATE TEMP TABLE t1 (a text, b text);
CREATE INDEX t1_ab_idx on t1 ((a || b));
CREATE TEMP TABLE t2 (ab text primary key);
INSERT INTO t1 VALUES ('a', 'b'), ('x', 'y');
INSERT INTO t2 VALUES ('ab'), ('xy');
set enable_seqscan = off;
set enable_indexscan = on;
set enable_bitmapscan = off;
set enable_sort = off;
explain (costs off)
SELECT * FROM
(SELECT a || b AS ab FROM t1
UNION ALL
SELECT * FROM t2) t
WHERE ab = 'ab';
QUERY PLAN
---------------------------------------------
Append
-> Index Scan using t1_ab_idx on t1
Index Cond: ((a || b) = 'ab'::text)
-> Index Only Scan using t2_pkey on t2
Index Cond: (ab = 'ab'::text)
(5 rows)
explain (costs off)
SELECT * FROM
(SELECT a || b AS ab FROM t1
UNION
SELECT * FROM t2) t
WHERE ab = 'ab';
QUERY PLAN
---------------------------------------------------
HashAggregate
Group Key: ((t1.a || t1.b))
-> Append
-> Index Scan using t1_ab_idx on t1
Index Cond: ((a || b) = 'ab'::text)
-> Index Only Scan using t2_pkey on t2
Index Cond: (ab = 'ab'::text)
(7 rows)
--
-- Test that ORDER BY for UNION ALL can be pushed down to inheritance
-- children.
--
CREATE TEMP TABLE t1c (b text, a text);
ALTER TABLE t1c INHERIT t1;
CREATE TEMP TABLE t2c (primary key (ab)) INHERITS (t2);
INSERT INTO t1c VALUES ('v', 'w'), ('c', 'd'), ('m', 'n'), ('e', 'f');
INSERT INTO t2c VALUES ('vw'), ('cd'), ('mn'), ('ef');
CREATE INDEX t1c_ab_idx on t1c ((a || b));
set enable_seqscan = on;
set enable_indexonlyscan = off;
explain (costs off)
SELECT * FROM
(SELECT a || b AS ab FROM t1
UNION ALL
SELECT ab FROM t2) t
ORDER BY 1 LIMIT 8;
Fix EXPLAIN's column alias output for mismatched child tables. If an inheritance/partitioning parent table is assigned some column alias names in the query, EXPLAIN mapped those aliases onto the child tables' columns by physical position, resulting in bogus output if a child table's columns aren't one-for-one with the parent's. To fix, make expand_single_inheritance_child() generate a correctly re-mapped column alias list, rather than just copying the parent RTE's alias node. (We have to fill the alias field, not just adjust the eref field, because ruleutils.c will ignore eref in favor of looking at the real column names.) This means that child tables will now always have alias fields in plan rtables, where before they might not have. That results in a rather substantial set of regression test output changes: EXPLAIN will now always show child tables with aliases that match the parent table (usually with "_N" appended for uniqueness). But that seems like a net positive for understandability, since the parent alias corresponds to something that actually appeared in the original query, while the child table names didn't. (Note that this does not change anything for cases where an explicit table alias was written in the query for the parent table; it just makes cases without such aliases behave similarly to that.) Hence, while we could avoid these subsidiary changes if we made inherit.c more complicated, we choose not to. Discussion: https://postgr.es/m/12424.1575168015@sss.pgh.pa.us
2019-12-03 01:08:10 +01:00
QUERY PLAN
-----------------------------------------------------
Limit
-> Merge Append
Sort Key: ((t1.a || t1.b))
-> Index Scan using t1_ab_idx on t1
Fix EXPLAIN's column alias output for mismatched child tables. If an inheritance/partitioning parent table is assigned some column alias names in the query, EXPLAIN mapped those aliases onto the child tables' columns by physical position, resulting in bogus output if a child table's columns aren't one-for-one with the parent's. To fix, make expand_single_inheritance_child() generate a correctly re-mapped column alias list, rather than just copying the parent RTE's alias node. (We have to fill the alias field, not just adjust the eref field, because ruleutils.c will ignore eref in favor of looking at the real column names.) This means that child tables will now always have alias fields in plan rtables, where before they might not have. That results in a rather substantial set of regression test output changes: EXPLAIN will now always show child tables with aliases that match the parent table (usually with "_N" appended for uniqueness). But that seems like a net positive for understandability, since the parent alias corresponds to something that actually appeared in the original query, while the child table names didn't. (Note that this does not change anything for cases where an explicit table alias was written in the query for the parent table; it just makes cases without such aliases behave similarly to that.) Hence, while we could avoid these subsidiary changes if we made inherit.c more complicated, we choose not to. Discussion: https://postgr.es/m/12424.1575168015@sss.pgh.pa.us
2019-12-03 01:08:10 +01:00
-> Index Scan using t1c_ab_idx on t1c t1_1
-> Index Scan using t2_pkey on t2
Fix EXPLAIN's column alias output for mismatched child tables. If an inheritance/partitioning parent table is assigned some column alias names in the query, EXPLAIN mapped those aliases onto the child tables' columns by physical position, resulting in bogus output if a child table's columns aren't one-for-one with the parent's. To fix, make expand_single_inheritance_child() generate a correctly re-mapped column alias list, rather than just copying the parent RTE's alias node. (We have to fill the alias field, not just adjust the eref field, because ruleutils.c will ignore eref in favor of looking at the real column names.) This means that child tables will now always have alias fields in plan rtables, where before they might not have. That results in a rather substantial set of regression test output changes: EXPLAIN will now always show child tables with aliases that match the parent table (usually with "_N" appended for uniqueness). But that seems like a net positive for understandability, since the parent alias corresponds to something that actually appeared in the original query, while the child table names didn't. (Note that this does not change anything for cases where an explicit table alias was written in the query for the parent table; it just makes cases without such aliases behave similarly to that.) Hence, while we could avoid these subsidiary changes if we made inherit.c more complicated, we choose not to. Discussion: https://postgr.es/m/12424.1575168015@sss.pgh.pa.us
2019-12-03 01:08:10 +01:00
-> Index Scan using t2c_pkey on t2c t2_1
(7 rows)
SELECT * FROM
(SELECT a || b AS ab FROM t1
UNION ALL
SELECT ab FROM t2) t
ORDER BY 1 LIMIT 8;
ab
----
ab
ab
cd
dc
ef
fe
mn
nm
(8 rows)
reset enable_seqscan;
reset enable_indexscan;
reset enable_bitmapscan;
reset enable_sort;
-- This simpler variant of the above test has been observed to fail differently
create table events (event_id int primary key);
create table other_events (event_id int primary key);
create table events_child () inherits (events);
explain (costs off)
select event_id
from (select event_id from events
union all
select event_id from other_events) ss
order by event_id;
QUERY PLAN
----------------------------------------------------------
Merge Append
Sort Key: events.event_id
-> Index Scan using events_pkey on events
-> Sort
Fix EXPLAIN's column alias output for mismatched child tables. If an inheritance/partitioning parent table is assigned some column alias names in the query, EXPLAIN mapped those aliases onto the child tables' columns by physical position, resulting in bogus output if a child table's columns aren't one-for-one with the parent's. To fix, make expand_single_inheritance_child() generate a correctly re-mapped column alias list, rather than just copying the parent RTE's alias node. (We have to fill the alias field, not just adjust the eref field, because ruleutils.c will ignore eref in favor of looking at the real column names.) This means that child tables will now always have alias fields in plan rtables, where before they might not have. That results in a rather substantial set of regression test output changes: EXPLAIN will now always show child tables with aliases that match the parent table (usually with "_N" appended for uniqueness). But that seems like a net positive for understandability, since the parent alias corresponds to something that actually appeared in the original query, while the child table names didn't. (Note that this does not change anything for cases where an explicit table alias was written in the query for the parent table; it just makes cases without such aliases behave similarly to that.) Hence, while we could avoid these subsidiary changes if we made inherit.c more complicated, we choose not to. Discussion: https://postgr.es/m/12424.1575168015@sss.pgh.pa.us
2019-12-03 01:08:10 +01:00
Sort Key: events_1.event_id
-> Seq Scan on events_child events_1
-> Index Scan using other_events_pkey on other_events
(7 rows)
drop table events_child, events, other_events;
reset enable_indexonlyscan;
Revisit handling of UNION ALL subqueries with non-Var output columns. In commit 57664ed25e5dea117158a2e663c29e60b3546e1c I tried to fix a bug reported by Teodor Sigaev by making non-simple-Var output columns distinct (by wrapping their expressions with dummy PlaceHolderVar nodes). This did not work too well. Commit b28ffd0fcc583c1811e5295279e7d4366c3cae6c fixed some ensuing problems with matching to child indexes, but per a recent report from Claus Stadler, constraint exclusion of UNION ALL subqueries was still broken, because constant-simplification didn't handle the injected PlaceHolderVars well either. On reflection, the original patch was quite misguided: there is no reason to expect that EquivalenceClass child members will be distinct. So instead of trying to make them so, we should ensure that we can cope with the situation when they're not. Accordingly, this patch reverts the code changes in the above-mentioned commits (though the regression test cases they added stay). Instead, I've added assorted defenses to make sure that duplicate EC child members don't cause any problems. Teodor's original problem ("MergeAppend child's targetlist doesn't match MergeAppend") is addressed more directly by revising prepare_sort_from_pathkeys to let the parent MergeAppend's sort list guide creation of each child's sort list. In passing, get rid of add_sort_column; as far as I can tell, testing for duplicate sort keys at this stage is dead code. Certainly it doesn't trigger often enough to be worth expending cycles on in ordinary queries. And keeping the test would've greatly complicated the new logic in prepare_sort_from_pathkeys, because comparing pathkey list entries against a previous output array requires that we not skip any entries in the list. Back-patch to 9.1, like the previous patches. The only known issue in this area that wasn't caused by the ill-advised previous patches was the MergeAppend planning failure, which of course is not relevant before 9.1. It's possible that we need some of the new defenses against duplicate child EC entries in older branches, but until there's some clear evidence of that I'm going to refrain from back-patching further.
2012-03-16 18:11:12 +01:00
-- Test constraint exclusion of UNION ALL subqueries
explain (costs off)
SELECT * FROM
(SELECT 1 AS t, * FROM tenk1 a
UNION ALL
SELECT 2 AS t, * FROM tenk1 b) c
WHERE t = 2;
QUERY PLAN
---------------------
Seq Scan on tenk1 b
(1 row)
Revisit handling of UNION ALL subqueries with non-Var output columns. In commit 57664ed25e5dea117158a2e663c29e60b3546e1c I tried to fix a bug reported by Teodor Sigaev by making non-simple-Var output columns distinct (by wrapping their expressions with dummy PlaceHolderVar nodes). This did not work too well. Commit b28ffd0fcc583c1811e5295279e7d4366c3cae6c fixed some ensuing problems with matching to child indexes, but per a recent report from Claus Stadler, constraint exclusion of UNION ALL subqueries was still broken, because constant-simplification didn't handle the injected PlaceHolderVars well either. On reflection, the original patch was quite misguided: there is no reason to expect that EquivalenceClass child members will be distinct. So instead of trying to make them so, we should ensure that we can cope with the situation when they're not. Accordingly, this patch reverts the code changes in the above-mentioned commits (though the regression test cases they added stay). Instead, I've added assorted defenses to make sure that duplicate EC child members don't cause any problems. Teodor's original problem ("MergeAppend child's targetlist doesn't match MergeAppend") is addressed more directly by revising prepare_sort_from_pathkeys to let the parent MergeAppend's sort list guide creation of each child's sort list. In passing, get rid of add_sort_column; as far as I can tell, testing for duplicate sort keys at this stage is dead code. Certainly it doesn't trigger often enough to be worth expending cycles on in ordinary queries. And keeping the test would've greatly complicated the new logic in prepare_sort_from_pathkeys, because comparing pathkey list entries against a previous output array requires that we not skip any entries in the list. Back-patch to 9.1, like the previous patches. The only known issue in this area that wasn't caused by the ill-advised previous patches was the MergeAppend planning failure, which of course is not relevant before 9.1. It's possible that we need some of the new defenses against duplicate child EC entries in older branches, but until there's some clear evidence of that I'm going to refrain from back-patching further.
2012-03-16 18:11:12 +01:00
-- Test that we push quals into UNION sub-selects only when it's safe
explain (costs off)
SELECT * FROM
(SELECT 1 AS t, 2 AS x
UNION
SELECT 2 AS t, 4 AS x) ss
WHERE x < 4
ORDER BY x;
QUERY PLAN
--------------------------------------------------
Sort
Sort Key: (2)
-> Unique
-> Sort
Sort Key: (1), (2)
-> Append
-> Result
-> Result
One-Time Filter: false
(9 rows)
SELECT * FROM
(SELECT 1 AS t, 2 AS x
UNION
SELECT 2 AS t, 4 AS x) ss
WHERE x < 4
ORDER BY x;
t | x
---+---
1 | 2
(1 row)
explain (costs off)
SELECT * FROM
(SELECT 1 AS t, generate_series(1,10) AS x
UNION
SELECT 2 AS t, 4 AS x) ss
WHERE x < 4
ORDER BY x;
QUERY PLAN
--------------------------------------------------------
Sort
Sort Key: ss.x
-> Subquery Scan on ss
Filter: (ss.x < 4)
-> HashAggregate
Group Key: (1), (generate_series(1, 10))
-> Append
Move targetlist SRF handling from expression evaluation to new executor node. Evaluation of set returning functions (SRFs_ in the targetlist (like SELECT generate_series(1,5)) so far was done in the expression evaluation (i.e. ExecEvalExpr()) and projection (i.e. ExecProject/ExecTargetList) code. This meant that most executor nodes performing projection, and most expression evaluation functions, had to deal with the possibility that an evaluated expression could return a set of return values. That's bad because it leads to repeated code in a lot of places. It also, and that's my (Andres's) motivation, made it a lot harder to implement a more efficient way of doing expression evaluation. To fix this, introduce a new executor node (ProjectSet) that can evaluate targetlists containing one or more SRFs. To avoid the complexity of the old way of handling nested expressions returning sets (e.g. having to pass up ExprDoneCond, and dealing with arguments to functions returning sets etc.), those SRFs can only be at the top level of the node's targetlist. The planner makes sure (via split_pathtarget_at_srfs()) that SRF evaluation is only necessary in ProjectSet nodes and that SRFs are only present at the top level of the node's targetlist. If there are nested SRFs the planner creates multiple stacked ProjectSet nodes. The ProjectSet nodes always get input from an underlying node. We also discussed and prototyped evaluating targetlist SRFs using ROWS FROM(), but that turned out to be more complicated than we'd hoped. While moving SRF evaluation to ProjectSet would allow to retain the old "least common multiple" behavior when multiple SRFs are present in one targetlist (i.e. continue returning rows until all SRFs are at the end of their input at the same time), we decided to instead only return rows till all SRFs are exhausted, returning NULL for already exhausted ones. We deemed the previous behavior to be too confusing, unexpected and actually not particularly useful. As a side effect, the previously prohibited case of multiple set returning arguments to a function, is now allowed. Not because it's particularly desirable, but because it ends up working and there seems to be no argument for adding code to prohibit it. Currently the behavior for COALESCE and CASE containing SRFs has changed, returning multiple rows from the expression, even when the SRF containing "arm" of the expression is not evaluated. That's because the SRFs are evaluated in a separate ProjectSet node. As that's quite confusing, we're likely to instead prohibit SRFs in those places. But that's still being discussed, and the code would reside in places not touched here, so that's a task for later. There's a lot of, now superfluous, code dealing with set return expressions around. But as the changes to get rid of those are verbose largely boring, it seems better for readability to keep the cleanup as a separate commit. Author: Tom Lane and Andres Freund Discussion: https://postgr.es/m/20160822214023.aaxz5l4igypowyri@alap3.anarazel.de
2017-01-18 21:46:50 +01:00
-> ProjectSet
-> Result
-> Result
Move targetlist SRF handling from expression evaluation to new executor node. Evaluation of set returning functions (SRFs_ in the targetlist (like SELECT generate_series(1,5)) so far was done in the expression evaluation (i.e. ExecEvalExpr()) and projection (i.e. ExecProject/ExecTargetList) code. This meant that most executor nodes performing projection, and most expression evaluation functions, had to deal with the possibility that an evaluated expression could return a set of return values. That's bad because it leads to repeated code in a lot of places. It also, and that's my (Andres's) motivation, made it a lot harder to implement a more efficient way of doing expression evaluation. To fix this, introduce a new executor node (ProjectSet) that can evaluate targetlists containing one or more SRFs. To avoid the complexity of the old way of handling nested expressions returning sets (e.g. having to pass up ExprDoneCond, and dealing with arguments to functions returning sets etc.), those SRFs can only be at the top level of the node's targetlist. The planner makes sure (via split_pathtarget_at_srfs()) that SRF evaluation is only necessary in ProjectSet nodes and that SRFs are only present at the top level of the node's targetlist. If there are nested SRFs the planner creates multiple stacked ProjectSet nodes. The ProjectSet nodes always get input from an underlying node. We also discussed and prototyped evaluating targetlist SRFs using ROWS FROM(), but that turned out to be more complicated than we'd hoped. While moving SRF evaluation to ProjectSet would allow to retain the old "least common multiple" behavior when multiple SRFs are present in one targetlist (i.e. continue returning rows until all SRFs are at the end of their input at the same time), we decided to instead only return rows till all SRFs are exhausted, returning NULL for already exhausted ones. We deemed the previous behavior to be too confusing, unexpected and actually not particularly useful. As a side effect, the previously prohibited case of multiple set returning arguments to a function, is now allowed. Not because it's particularly desirable, but because it ends up working and there seems to be no argument for adding code to prohibit it. Currently the behavior for COALESCE and CASE containing SRFs has changed, returning multiple rows from the expression, even when the SRF containing "arm" of the expression is not evaluated. That's because the SRFs are evaluated in a separate ProjectSet node. As that's quite confusing, we're likely to instead prohibit SRFs in those places. But that's still being discussed, and the code would reside in places not touched here, so that's a task for later. There's a lot of, now superfluous, code dealing with set return expressions around. But as the changes to get rid of those are verbose largely boring, it seems better for readability to keep the cleanup as a separate commit. Author: Tom Lane and Andres Freund Discussion: https://postgr.es/m/20160822214023.aaxz5l4igypowyri@alap3.anarazel.de
2017-01-18 21:46:50 +01:00
(10 rows)
SELECT * FROM
(SELECT 1 AS t, generate_series(1,10) AS x
UNION
SELECT 2 AS t, 4 AS x) ss
WHERE x < 4
ORDER BY x;
t | x
---+---
1 | 1
1 | 2
1 | 3
(3 rows)
explain (costs off)
SELECT * FROM
(SELECT 1 AS t, (random()*3)::int AS x
UNION
SELECT 2 AS t, 4 AS x) ss
WHERE x > 3
ORDER BY x;
QUERY PLAN
------------------------------------------------------------------------------------
Sort
Sort Key: ss.x
-> Subquery Scan on ss
Filter: (ss.x > 3)
-> Unique
-> Sort
Sort Key: (1), (((random() * '3'::double precision))::integer)
-> Append
-> Result
-> Result
(10 rows)
SELECT * FROM
(SELECT 1 AS t, (random()*3)::int AS x
UNION
SELECT 2 AS t, 4 AS x) ss
WHERE x > 3
ORDER BY x;
t | x
---+---
2 | 4
(1 row)
Repair issues with faulty generation of merge-append plans. create_merge_append_plan failed to honor the CP_EXACT_TLIST flag: it would generate the expected targetlist but then it felt free to add resjunk sort targets to it. This demonstrably leads to assertion failures in v11 and HEAD, and it's probably just accidental that we don't see the same in older branches. I've not looked into whether there would be any real-world consequences in non-assert builds. In HEAD, create_append_plan has sprouted the same problem, so fix that too (although we do not have any test cases that seem able to reach that bug). This is an oversight in commit 3fc6e2d7f which invented the CP_EXACT_TLIST flag, so back-patch to 9.6 where that came in. convert_subquery_pathkeys would create pathkeys for subquery output values if they match any EquivalenceClass known in the outer query and are available in the subquery's syntactic targetlist. However, the second part of that condition is wrong, because such values might not appear in the subquery relation's reltarget list, which would mean that they couldn't be accessed above the level of the subquery scan. We must check that they appear in the reltarget list, instead. This can lead to dropping knowledge about the subquery's sort ordering, but I believe it's okay, because any sort key that the outer query actually has any interest in would appear in the reltarget list. This second issue is of very long standing, but right now there's no evidence that it causes observable problems before 9.6, so I refrained from back-patching further than that. We can revisit that choice if somebody finds a way to make it cause problems in older branches. (Developing useful test cases for these issues is really problematic; fixing convert_subquery_pathkeys removes the only known way to exhibit the create_merge_append_plan bug, and neither of the test cases added by this patch causes a problem in all branches, even when considering the issues separately.) The second issue explains bug #15795 from Suresh Kumar R ("could not find pathkey item to sort" with nested DISTINCT queries). I stumbled across the first issue while investigating that. Discussion: https://postgr.es/m/15795-fadb56c8e44ee73c@postgresql.org
2019-05-09 22:52:48 +02:00
-- Test cases where the native ordering of a sub-select has more pathkeys
-- than the outer query cares about
explain (costs off)
select distinct q1 from
(select distinct * from int8_tbl i81
union all
select distinct * from int8_tbl i82) ss
where q2 = q2;
Revert "Optimize order of GROUP BY keys". This reverts commit db0d67db2401eb6238ccc04c6407a4fd4f985832 and several follow-on fixes. The idea of making a cost-based choice of the order of the sorting columns is not fundamentally unsound, but it requires cost information and data statistics that we don't really have. For example, relying on procost to distinguish the relative costs of different sort comparators is pretty pointless so long as most such comparator functions are labeled with cost 1.0. Moreover, estimating the number of comparisons done by Quicksort requires more than just an estimate of the number of distinct values in the input: you also need some idea of the sizes of the larger groups, if you want an estimate that's good to better than a factor of three or so. That's data that's often unknown or not very reliable. Worse, to arrive at estimates of the number of calls made to the lower-order-column comparison functions, the code needs to make estimates of the numbers of distinct values of multiple columns, which are necessarily even less trustworthy than per-column stats. Even if all the inputs are perfectly reliable, the cost algorithm as-implemented cannot offer useful information about how to order sorting columns beyond the point at which the average group size is estimated to drop to 1. Close inspection of the code added by db0d67db2 shows that there are also multiple small bugs. These could have been fixed, but there's not much point if we don't trust the estimates to be accurate in-principle. Finally, the changes in cost_sort's behavior made for very large changes (often a factor of 2 or so) in the cost estimates for all sorting operations, not only those for multi-column GROUP BY. That naturally changes plan choices in many situations, and there's precious little evidence to show that the changes are for the better. Given the above doubts about whether the new estimates are really trustworthy, it's hard to summon much confidence that these changes are better on the average. Since we're hard up against the release deadline for v15, let's revert these changes for now. We can always try again later. Note: in v15, I left T_PathKeyInfo in place in nodes.h even though it's unreferenced. Removing it would be an ABI break, and it seems a bit late in the release cycle for that. Discussion: https://postgr.es/m/TYAPR01MB586665EB5FB2C3807E893941F5579@TYAPR01MB5866.jpnprd01.prod.outlook.com
2022-10-03 16:56:16 +02:00
QUERY PLAN
----------------------------------------------------------
Unique
-> Merge Append
Sort Key: "*SELECT* 1".q1
Repair issues with faulty generation of merge-append plans. create_merge_append_plan failed to honor the CP_EXACT_TLIST flag: it would generate the expected targetlist but then it felt free to add resjunk sort targets to it. This demonstrably leads to assertion failures in v11 and HEAD, and it's probably just accidental that we don't see the same in older branches. I've not looked into whether there would be any real-world consequences in non-assert builds. In HEAD, create_append_plan has sprouted the same problem, so fix that too (although we do not have any test cases that seem able to reach that bug). This is an oversight in commit 3fc6e2d7f which invented the CP_EXACT_TLIST flag, so back-patch to 9.6 where that came in. convert_subquery_pathkeys would create pathkeys for subquery output values if they match any EquivalenceClass known in the outer query and are available in the subquery's syntactic targetlist. However, the second part of that condition is wrong, because such values might not appear in the subquery relation's reltarget list, which would mean that they couldn't be accessed above the level of the subquery scan. We must check that they appear in the reltarget list, instead. This can lead to dropping knowledge about the subquery's sort ordering, but I believe it's okay, because any sort key that the outer query actually has any interest in would appear in the reltarget list. This second issue is of very long standing, but right now there's no evidence that it causes observable problems before 9.6, so I refrained from back-patching further than that. We can revisit that choice if somebody finds a way to make it cause problems in older branches. (Developing useful test cases for these issues is really problematic; fixing convert_subquery_pathkeys removes the only known way to exhibit the create_merge_append_plan bug, and neither of the test cases added by this patch causes a problem in all branches, even when considering the issues separately.) The second issue explains bug #15795 from Suresh Kumar R ("could not find pathkey item to sort" with nested DISTINCT queries). I stumbled across the first issue while investigating that. Discussion: https://postgr.es/m/15795-fadb56c8e44ee73c@postgresql.org
2019-05-09 22:52:48 +02:00
-> Subquery Scan on "*SELECT* 1"
Revert "Optimize order of GROUP BY keys". This reverts commit db0d67db2401eb6238ccc04c6407a4fd4f985832 and several follow-on fixes. The idea of making a cost-based choice of the order of the sorting columns is not fundamentally unsound, but it requires cost information and data statistics that we don't really have. For example, relying on procost to distinguish the relative costs of different sort comparators is pretty pointless so long as most such comparator functions are labeled with cost 1.0. Moreover, estimating the number of comparisons done by Quicksort requires more than just an estimate of the number of distinct values in the input: you also need some idea of the sizes of the larger groups, if you want an estimate that's good to better than a factor of three or so. That's data that's often unknown or not very reliable. Worse, to arrive at estimates of the number of calls made to the lower-order-column comparison functions, the code needs to make estimates of the numbers of distinct values of multiple columns, which are necessarily even less trustworthy than per-column stats. Even if all the inputs are perfectly reliable, the cost algorithm as-implemented cannot offer useful information about how to order sorting columns beyond the point at which the average group size is estimated to drop to 1. Close inspection of the code added by db0d67db2 shows that there are also multiple small bugs. These could have been fixed, but there's not much point if we don't trust the estimates to be accurate in-principle. Finally, the changes in cost_sort's behavior made for very large changes (often a factor of 2 or so) in the cost estimates for all sorting operations, not only those for multi-column GROUP BY. That naturally changes plan choices in many situations, and there's precious little evidence to show that the changes are for the better. Given the above doubts about whether the new estimates are really trustworthy, it's hard to summon much confidence that these changes are better on the average. Since we're hard up against the release deadline for v15, let's revert these changes for now. We can always try again later. Note: in v15, I left T_PathKeyInfo in place in nodes.h even though it's unreferenced. Removing it would be an ABI break, and it seems a bit late in the release cycle for that. Discussion: https://postgr.es/m/TYAPR01MB586665EB5FB2C3807E893941F5579@TYAPR01MB5866.jpnprd01.prod.outlook.com
2022-10-03 16:56:16 +02:00
-> Unique
-> Sort
Sort Key: i81.q1, i81.q2
-> Seq Scan on int8_tbl i81
Filter: (q2 IS NOT NULL)
Repair issues with faulty generation of merge-append plans. create_merge_append_plan failed to honor the CP_EXACT_TLIST flag: it would generate the expected targetlist but then it felt free to add resjunk sort targets to it. This demonstrably leads to assertion failures in v11 and HEAD, and it's probably just accidental that we don't see the same in older branches. I've not looked into whether there would be any real-world consequences in non-assert builds. In HEAD, create_append_plan has sprouted the same problem, so fix that too (although we do not have any test cases that seem able to reach that bug). This is an oversight in commit 3fc6e2d7f which invented the CP_EXACT_TLIST flag, so back-patch to 9.6 where that came in. convert_subquery_pathkeys would create pathkeys for subquery output values if they match any EquivalenceClass known in the outer query and are available in the subquery's syntactic targetlist. However, the second part of that condition is wrong, because such values might not appear in the subquery relation's reltarget list, which would mean that they couldn't be accessed above the level of the subquery scan. We must check that they appear in the reltarget list, instead. This can lead to dropping knowledge about the subquery's sort ordering, but I believe it's okay, because any sort key that the outer query actually has any interest in would appear in the reltarget list. This second issue is of very long standing, but right now there's no evidence that it causes observable problems before 9.6, so I refrained from back-patching further than that. We can revisit that choice if somebody finds a way to make it cause problems in older branches. (Developing useful test cases for these issues is really problematic; fixing convert_subquery_pathkeys removes the only known way to exhibit the create_merge_append_plan bug, and neither of the test cases added by this patch causes a problem in all branches, even when considering the issues separately.) The second issue explains bug #15795 from Suresh Kumar R ("could not find pathkey item to sort" with nested DISTINCT queries). I stumbled across the first issue while investigating that. Discussion: https://postgr.es/m/15795-fadb56c8e44ee73c@postgresql.org
2019-05-09 22:52:48 +02:00
-> Subquery Scan on "*SELECT* 2"
Revert "Optimize order of GROUP BY keys". This reverts commit db0d67db2401eb6238ccc04c6407a4fd4f985832 and several follow-on fixes. The idea of making a cost-based choice of the order of the sorting columns is not fundamentally unsound, but it requires cost information and data statistics that we don't really have. For example, relying on procost to distinguish the relative costs of different sort comparators is pretty pointless so long as most such comparator functions are labeled with cost 1.0. Moreover, estimating the number of comparisons done by Quicksort requires more than just an estimate of the number of distinct values in the input: you also need some idea of the sizes of the larger groups, if you want an estimate that's good to better than a factor of three or so. That's data that's often unknown or not very reliable. Worse, to arrive at estimates of the number of calls made to the lower-order-column comparison functions, the code needs to make estimates of the numbers of distinct values of multiple columns, which are necessarily even less trustworthy than per-column stats. Even if all the inputs are perfectly reliable, the cost algorithm as-implemented cannot offer useful information about how to order sorting columns beyond the point at which the average group size is estimated to drop to 1. Close inspection of the code added by db0d67db2 shows that there are also multiple small bugs. These could have been fixed, but there's not much point if we don't trust the estimates to be accurate in-principle. Finally, the changes in cost_sort's behavior made for very large changes (often a factor of 2 or so) in the cost estimates for all sorting operations, not only those for multi-column GROUP BY. That naturally changes plan choices in many situations, and there's precious little evidence to show that the changes are for the better. Given the above doubts about whether the new estimates are really trustworthy, it's hard to summon much confidence that these changes are better on the average. Since we're hard up against the release deadline for v15, let's revert these changes for now. We can always try again later. Note: in v15, I left T_PathKeyInfo in place in nodes.h even though it's unreferenced. Removing it would be an ABI break, and it seems a bit late in the release cycle for that. Discussion: https://postgr.es/m/TYAPR01MB586665EB5FB2C3807E893941F5579@TYAPR01MB5866.jpnprd01.prod.outlook.com
2022-10-03 16:56:16 +02:00
-> Unique
-> Sort
Sort Key: i82.q1, i82.q2
-> Seq Scan on int8_tbl i82
Filter: (q2 IS NOT NULL)
(15 rows)
Repair issues with faulty generation of merge-append plans. create_merge_append_plan failed to honor the CP_EXACT_TLIST flag: it would generate the expected targetlist but then it felt free to add resjunk sort targets to it. This demonstrably leads to assertion failures in v11 and HEAD, and it's probably just accidental that we don't see the same in older branches. I've not looked into whether there would be any real-world consequences in non-assert builds. In HEAD, create_append_plan has sprouted the same problem, so fix that too (although we do not have any test cases that seem able to reach that bug). This is an oversight in commit 3fc6e2d7f which invented the CP_EXACT_TLIST flag, so back-patch to 9.6 where that came in. convert_subquery_pathkeys would create pathkeys for subquery output values if they match any EquivalenceClass known in the outer query and are available in the subquery's syntactic targetlist. However, the second part of that condition is wrong, because such values might not appear in the subquery relation's reltarget list, which would mean that they couldn't be accessed above the level of the subquery scan. We must check that they appear in the reltarget list, instead. This can lead to dropping knowledge about the subquery's sort ordering, but I believe it's okay, because any sort key that the outer query actually has any interest in would appear in the reltarget list. This second issue is of very long standing, but right now there's no evidence that it causes observable problems before 9.6, so I refrained from back-patching further than that. We can revisit that choice if somebody finds a way to make it cause problems in older branches. (Developing useful test cases for these issues is really problematic; fixing convert_subquery_pathkeys removes the only known way to exhibit the create_merge_append_plan bug, and neither of the test cases added by this patch causes a problem in all branches, even when considering the issues separately.) The second issue explains bug #15795 from Suresh Kumar R ("could not find pathkey item to sort" with nested DISTINCT queries). I stumbled across the first issue while investigating that. Discussion: https://postgr.es/m/15795-fadb56c8e44ee73c@postgresql.org
2019-05-09 22:52:48 +02:00
select distinct q1 from
(select distinct * from int8_tbl i81
union all
select distinct * from int8_tbl i82) ss
where q2 = q2;
q1
------------------
123
4567890123456789
(2 rows)
explain (costs off)
select distinct q1 from
(select distinct * from int8_tbl i81
union all
select distinct * from int8_tbl i82) ss
where -q1 = q2;
Revert "Optimize order of GROUP BY keys". This reverts commit db0d67db2401eb6238ccc04c6407a4fd4f985832 and several follow-on fixes. The idea of making a cost-based choice of the order of the sorting columns is not fundamentally unsound, but it requires cost information and data statistics that we don't really have. For example, relying on procost to distinguish the relative costs of different sort comparators is pretty pointless so long as most such comparator functions are labeled with cost 1.0. Moreover, estimating the number of comparisons done by Quicksort requires more than just an estimate of the number of distinct values in the input: you also need some idea of the sizes of the larger groups, if you want an estimate that's good to better than a factor of three or so. That's data that's often unknown or not very reliable. Worse, to arrive at estimates of the number of calls made to the lower-order-column comparison functions, the code needs to make estimates of the numbers of distinct values of multiple columns, which are necessarily even less trustworthy than per-column stats. Even if all the inputs are perfectly reliable, the cost algorithm as-implemented cannot offer useful information about how to order sorting columns beyond the point at which the average group size is estimated to drop to 1. Close inspection of the code added by db0d67db2 shows that there are also multiple small bugs. These could have been fixed, but there's not much point if we don't trust the estimates to be accurate in-principle. Finally, the changes in cost_sort's behavior made for very large changes (often a factor of 2 or so) in the cost estimates for all sorting operations, not only those for multi-column GROUP BY. That naturally changes plan choices in many situations, and there's precious little evidence to show that the changes are for the better. Given the above doubts about whether the new estimates are really trustworthy, it's hard to summon much confidence that these changes are better on the average. Since we're hard up against the release deadline for v15, let's revert these changes for now. We can always try again later. Note: in v15, I left T_PathKeyInfo in place in nodes.h even though it's unreferenced. Removing it would be an ABI break, and it seems a bit late in the release cycle for that. Discussion: https://postgr.es/m/TYAPR01MB586665EB5FB2C3807E893941F5579@TYAPR01MB5866.jpnprd01.prod.outlook.com
2022-10-03 16:56:16 +02:00
QUERY PLAN
--------------------------------------------------------
Unique
-> Merge Append
Sort Key: "*SELECT* 1".q1
Repair issues with faulty generation of merge-append plans. create_merge_append_plan failed to honor the CP_EXACT_TLIST flag: it would generate the expected targetlist but then it felt free to add resjunk sort targets to it. This demonstrably leads to assertion failures in v11 and HEAD, and it's probably just accidental that we don't see the same in older branches. I've not looked into whether there would be any real-world consequences in non-assert builds. In HEAD, create_append_plan has sprouted the same problem, so fix that too (although we do not have any test cases that seem able to reach that bug). This is an oversight in commit 3fc6e2d7f which invented the CP_EXACT_TLIST flag, so back-patch to 9.6 where that came in. convert_subquery_pathkeys would create pathkeys for subquery output values if they match any EquivalenceClass known in the outer query and are available in the subquery's syntactic targetlist. However, the second part of that condition is wrong, because such values might not appear in the subquery relation's reltarget list, which would mean that they couldn't be accessed above the level of the subquery scan. We must check that they appear in the reltarget list, instead. This can lead to dropping knowledge about the subquery's sort ordering, but I believe it's okay, because any sort key that the outer query actually has any interest in would appear in the reltarget list. This second issue is of very long standing, but right now there's no evidence that it causes observable problems before 9.6, so I refrained from back-patching further than that. We can revisit that choice if somebody finds a way to make it cause problems in older branches. (Developing useful test cases for these issues is really problematic; fixing convert_subquery_pathkeys removes the only known way to exhibit the create_merge_append_plan bug, and neither of the test cases added by this patch causes a problem in all branches, even when considering the issues separately.) The second issue explains bug #15795 from Suresh Kumar R ("could not find pathkey item to sort" with nested DISTINCT queries). I stumbled across the first issue while investigating that. Discussion: https://postgr.es/m/15795-fadb56c8e44ee73c@postgresql.org
2019-05-09 22:52:48 +02:00
-> Subquery Scan on "*SELECT* 1"
Revert "Optimize order of GROUP BY keys". This reverts commit db0d67db2401eb6238ccc04c6407a4fd4f985832 and several follow-on fixes. The idea of making a cost-based choice of the order of the sorting columns is not fundamentally unsound, but it requires cost information and data statistics that we don't really have. For example, relying on procost to distinguish the relative costs of different sort comparators is pretty pointless so long as most such comparator functions are labeled with cost 1.0. Moreover, estimating the number of comparisons done by Quicksort requires more than just an estimate of the number of distinct values in the input: you also need some idea of the sizes of the larger groups, if you want an estimate that's good to better than a factor of three or so. That's data that's often unknown or not very reliable. Worse, to arrive at estimates of the number of calls made to the lower-order-column comparison functions, the code needs to make estimates of the numbers of distinct values of multiple columns, which are necessarily even less trustworthy than per-column stats. Even if all the inputs are perfectly reliable, the cost algorithm as-implemented cannot offer useful information about how to order sorting columns beyond the point at which the average group size is estimated to drop to 1. Close inspection of the code added by db0d67db2 shows that there are also multiple small bugs. These could have been fixed, but there's not much point if we don't trust the estimates to be accurate in-principle. Finally, the changes in cost_sort's behavior made for very large changes (often a factor of 2 or so) in the cost estimates for all sorting operations, not only those for multi-column GROUP BY. That naturally changes plan choices in many situations, and there's precious little evidence to show that the changes are for the better. Given the above doubts about whether the new estimates are really trustworthy, it's hard to summon much confidence that these changes are better on the average. Since we're hard up against the release deadline for v15, let's revert these changes for now. We can always try again later. Note: in v15, I left T_PathKeyInfo in place in nodes.h even though it's unreferenced. Removing it would be an ABI break, and it seems a bit late in the release cycle for that. Discussion: https://postgr.es/m/TYAPR01MB586665EB5FB2C3807E893941F5579@TYAPR01MB5866.jpnprd01.prod.outlook.com
2022-10-03 16:56:16 +02:00
-> Unique
-> Sort
Sort Key: i81.q1, i81.q2
-> Seq Scan on int8_tbl i81
Filter: ((- q1) = q2)
Repair issues with faulty generation of merge-append plans. create_merge_append_plan failed to honor the CP_EXACT_TLIST flag: it would generate the expected targetlist but then it felt free to add resjunk sort targets to it. This demonstrably leads to assertion failures in v11 and HEAD, and it's probably just accidental that we don't see the same in older branches. I've not looked into whether there would be any real-world consequences in non-assert builds. In HEAD, create_append_plan has sprouted the same problem, so fix that too (although we do not have any test cases that seem able to reach that bug). This is an oversight in commit 3fc6e2d7f which invented the CP_EXACT_TLIST flag, so back-patch to 9.6 where that came in. convert_subquery_pathkeys would create pathkeys for subquery output values if they match any EquivalenceClass known in the outer query and are available in the subquery's syntactic targetlist. However, the second part of that condition is wrong, because such values might not appear in the subquery relation's reltarget list, which would mean that they couldn't be accessed above the level of the subquery scan. We must check that they appear in the reltarget list, instead. This can lead to dropping knowledge about the subquery's sort ordering, but I believe it's okay, because any sort key that the outer query actually has any interest in would appear in the reltarget list. This second issue is of very long standing, but right now there's no evidence that it causes observable problems before 9.6, so I refrained from back-patching further than that. We can revisit that choice if somebody finds a way to make it cause problems in older branches. (Developing useful test cases for these issues is really problematic; fixing convert_subquery_pathkeys removes the only known way to exhibit the create_merge_append_plan bug, and neither of the test cases added by this patch causes a problem in all branches, even when considering the issues separately.) The second issue explains bug #15795 from Suresh Kumar R ("could not find pathkey item to sort" with nested DISTINCT queries). I stumbled across the first issue while investigating that. Discussion: https://postgr.es/m/15795-fadb56c8e44ee73c@postgresql.org
2019-05-09 22:52:48 +02:00
-> Subquery Scan on "*SELECT* 2"
Revert "Optimize order of GROUP BY keys". This reverts commit db0d67db2401eb6238ccc04c6407a4fd4f985832 and several follow-on fixes. The idea of making a cost-based choice of the order of the sorting columns is not fundamentally unsound, but it requires cost information and data statistics that we don't really have. For example, relying on procost to distinguish the relative costs of different sort comparators is pretty pointless so long as most such comparator functions are labeled with cost 1.0. Moreover, estimating the number of comparisons done by Quicksort requires more than just an estimate of the number of distinct values in the input: you also need some idea of the sizes of the larger groups, if you want an estimate that's good to better than a factor of three or so. That's data that's often unknown or not very reliable. Worse, to arrive at estimates of the number of calls made to the lower-order-column comparison functions, the code needs to make estimates of the numbers of distinct values of multiple columns, which are necessarily even less trustworthy than per-column stats. Even if all the inputs are perfectly reliable, the cost algorithm as-implemented cannot offer useful information about how to order sorting columns beyond the point at which the average group size is estimated to drop to 1. Close inspection of the code added by db0d67db2 shows that there are also multiple small bugs. These could have been fixed, but there's not much point if we don't trust the estimates to be accurate in-principle. Finally, the changes in cost_sort's behavior made for very large changes (often a factor of 2 or so) in the cost estimates for all sorting operations, not only those for multi-column GROUP BY. That naturally changes plan choices in many situations, and there's precious little evidence to show that the changes are for the better. Given the above doubts about whether the new estimates are really trustworthy, it's hard to summon much confidence that these changes are better on the average. Since we're hard up against the release deadline for v15, let's revert these changes for now. We can always try again later. Note: in v15, I left T_PathKeyInfo in place in nodes.h even though it's unreferenced. Removing it would be an ABI break, and it seems a bit late in the release cycle for that. Discussion: https://postgr.es/m/TYAPR01MB586665EB5FB2C3807E893941F5579@TYAPR01MB5866.jpnprd01.prod.outlook.com
2022-10-03 16:56:16 +02:00
-> Unique
-> Sort
Sort Key: i82.q1, i82.q2
-> Seq Scan on int8_tbl i82
Filter: ((- q1) = q2)
(15 rows)
Repair issues with faulty generation of merge-append plans. create_merge_append_plan failed to honor the CP_EXACT_TLIST flag: it would generate the expected targetlist but then it felt free to add resjunk sort targets to it. This demonstrably leads to assertion failures in v11 and HEAD, and it's probably just accidental that we don't see the same in older branches. I've not looked into whether there would be any real-world consequences in non-assert builds. In HEAD, create_append_plan has sprouted the same problem, so fix that too (although we do not have any test cases that seem able to reach that bug). This is an oversight in commit 3fc6e2d7f which invented the CP_EXACT_TLIST flag, so back-patch to 9.6 where that came in. convert_subquery_pathkeys would create pathkeys for subquery output values if they match any EquivalenceClass known in the outer query and are available in the subquery's syntactic targetlist. However, the second part of that condition is wrong, because such values might not appear in the subquery relation's reltarget list, which would mean that they couldn't be accessed above the level of the subquery scan. We must check that they appear in the reltarget list, instead. This can lead to dropping knowledge about the subquery's sort ordering, but I believe it's okay, because any sort key that the outer query actually has any interest in would appear in the reltarget list. This second issue is of very long standing, but right now there's no evidence that it causes observable problems before 9.6, so I refrained from back-patching further than that. We can revisit that choice if somebody finds a way to make it cause problems in older branches. (Developing useful test cases for these issues is really problematic; fixing convert_subquery_pathkeys removes the only known way to exhibit the create_merge_append_plan bug, and neither of the test cases added by this patch causes a problem in all branches, even when considering the issues separately.) The second issue explains bug #15795 from Suresh Kumar R ("could not find pathkey item to sort" with nested DISTINCT queries). I stumbled across the first issue while investigating that. Discussion: https://postgr.es/m/15795-fadb56c8e44ee73c@postgresql.org
2019-05-09 22:52:48 +02:00
select distinct q1 from
(select distinct * from int8_tbl i81
union all
select distinct * from int8_tbl i82) ss
where -q1 = q2;
q1
------------------
4567890123456789
(1 row)
-- Test proper handling of parameterized appendrel paths when the
-- potential join qual is expensive
create function expensivefunc(int) returns int
language plpgsql immutable strict cost 10000
as $$begin return $1; end$$;
create temp table t3 as select generate_series(-1000,1000) as x;
create index t3i on t3 (expensivefunc(x));
analyze t3;
explain (costs off)
select * from
(select * from t3 a union all select * from t3 b) ss
join int4_tbl on f1 = expensivefunc(x);
QUERY PLAN
------------------------------------------------------------
Nested Loop
-> Seq Scan on int4_tbl
-> Append
-> Index Scan using t3i on t3 a
Index Cond: (expensivefunc(x) = int4_tbl.f1)
-> Index Scan using t3i on t3 b
Index Cond: (expensivefunc(x) = int4_tbl.f1)
(7 rows)
select * from
(select * from t3 a union all select * from t3 b) ss
join int4_tbl on f1 = expensivefunc(x);
x | f1
---+----
0 | 0
0 | 0
(2 rows)
drop table t3;
drop function expensivefunc(int);
-- Test handling of appendrel quals that const-simplify into an AND
explain (costs off)
select * from
(select *, 0 as x from int8_tbl a
union all
select *, 1 as x from int8_tbl b) ss
where (x = 0) or (q1 >= q2 and q1 <= q2);
QUERY PLAN
---------------------------------------------
Append
-> Seq Scan on int8_tbl a
-> Seq Scan on int8_tbl b
Filter: ((q1 >= q2) AND (q1 <= q2))
(4 rows)
select * from
(select *, 0 as x from int8_tbl a
union all
select *, 1 as x from int8_tbl b) ss
where (x = 0) or (q1 >= q2 and q1 <= q2);
q1 | q2 | x
------------------+-------------------+---
123 | 456 | 0
123 | 4567890123456789 | 0
4567890123456789 | 123 | 0
4567890123456789 | 4567890123456789 | 0
4567890123456789 | -4567890123456789 | 0
4567890123456789 | 4567890123456789 | 1
(6 rows)
--
-- Test the planner's ability to produce cheap startup plans with Append nodes
--
-- Ensure we get a Nested Loop join between tenk1 and tenk2
explain (costs off)
select t1.unique1 from tenk1 t1
inner join tenk2 t2 on t1.tenthous = t2.tenthous and t2.thousand = 0
union all
(values(1)) limit 1;
QUERY PLAN
--------------------------------------------------------
Limit
-> Append
-> Nested Loop
Join Filter: (t1.tenthous = t2.tenthous)
-> Seq Scan on tenk1 t1
-> Materialize
-> Seq Scan on tenk2 t2
Filter: (thousand = 0)
-> Result
(9 rows)
-- Ensure there is no problem if cheapest_startup_path is NULL
explain (costs off)
select * from tenk1 t1
left join lateral
(select t1.tenthous from tenk2 t2 union all (values(1)))
on true limit 1;
QUERY PLAN
-------------------------------------------------------------------
Limit
-> Nested Loop Left Join
-> Seq Scan on tenk1 t1
-> Append
-> Index Only Scan using tenk2_hundred on tenk2 t2
-> Result
(6 rows)