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postgresql/src/test/regress/expected/union.out
Tom Lane f4c7c410ee Revert "Optimize order of GROUP BY keys". 
This reverts commit db0d67db24 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 10:56:16 -04:00

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--
-- UNION (also INTERSECT, EXCEPT)
--
-- Simple UNION constructs
SELECT 1 AS two UNION SELECT 2 ORDER BY 1;
two
-----
1
2
(2 rows)
SELECT 1 AS one UNION SELECT 1 ORDER BY 1;
one
-----
1
(1 row)
SELECT 1 AS two UNION ALL SELECT 2;
two
-----
1
2
(2 rows)
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;
three
-------
1
2
3
(3 rows)
SELECT 1 AS two UNION SELECT 2 UNION SELECT 2 ORDER BY 1;
two
-----
1
2
(2 rows)
SELECT 1 AS three UNION SELECT 2 UNION ALL SELECT 2 ORDER BY 1;
three
-------
1
2
2
(3 rows)
SELECT 1.1 AS two UNION SELECT 2.2 ORDER BY 1;
two
-----
1.1
2.2
(2 rows)
-- Mixed types
SELECT 1.1 AS two UNION SELECT 2 ORDER BY 1;
two
-----
1.1
2
(2 rows)
SELECT 1 AS two UNION SELECT 2.2 ORDER BY 1;
two
-----
1
2.2
(2 rows)
SELECT 1 AS one UNION SELECT 1.0::float8 ORDER BY 1;
one
-----
1
(1 row)
SELECT 1.1 AS two UNION ALL SELECT 2 ORDER BY 1;
two
-----
1.1
2
(2 rows)
SELECT 1.0::float8 AS two UNION ALL SELECT 1 ORDER BY 1;
two
-----
1
1
(2 rows)
SELECT 1.1 AS three UNION SELECT 2 UNION SELECT 3 ORDER BY 1;
three
-------
1.1
2
3
(3 rows)
SELECT 1.1::float8 AS two UNION SELECT 2 UNION SELECT 2.0::float8 ORDER BY 1;
two
-----
1.1
2
(2 rows)
SELECT 1.1 AS three UNION SELECT 2 UNION ALL SELECT 2 ORDER BY 1;
three
-------
1.1
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)
--
-- Try testing from tables...
--
SELECT f1 AS five FROM FLOAT8_TBL
UNION
SELECT f1 FROM FLOAT8_TBL
ORDER BY 1;
five
-----------------------
-1.2345678901234e+200
-1004.3
-34.84
-1.2345678901234e-200
0
(5 rows)
SELECT f1 AS ten FROM FLOAT8_TBL
UNION ALL
SELECT f1 FROM FLOAT8_TBL;
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)
SELECT f1 AS nine FROM FLOAT8_TBL
UNION
SELECT f1 FROM INT4_TBL
ORDER BY 1;
nine
-----------------------
-1.2345678901234e+200
-2147483647
-123456
-1004.3
-34.84
-1.2345678901234e-200
0
123456
2147483647
(9 rows)
SELECT f1 AS ten FROM FLOAT8_TBL
UNION ALL
SELECT f1 FROM INT4_TBL;
ten
-----------------------
0
-34.84
-1004.3
-1.2345678901234e+200
-1.2345678901234e-200
0
123456
-123456
2147483647
-2147483647
(10 rows)
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;
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
-------
a
ab
abcd
(3 rows)
SELECT f1 AS three FROM VARCHAR_TBL
UNION
SELECT CAST(f1 AS varchar) FROM CHAR_TBL
ORDER BY 1;
three
-------
a
ab
abcd
(3 rows)
SELECT f1 AS eight FROM VARCHAR_TBL
UNION ALL
SELECT f1 FROM CHAR_TBL;
eight
-------
a
ab
abcd
abcd
a
ab
abcd
abcd
(8 rows)
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;
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
-> Sort
Sort Key: tenk1.unique1
-> Append
-> Index Only Scan using tenk1_unique1 on tenk1
-> Seq Scan on tenk1 tenk1_1
(7 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 (100::money), (200::money)) _(x) union select x from (values (100::money), (300::money)) _(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 (100::money), (200::money)) _(x) union select x from (values (100::money), (300::money)) _(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[100::money]), (array[200::money])) _(x) union select x from (values (array[100::money]), (array[300::money])) _(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[100::money]), (array[200::money])) _(x) union select x from (values (array[100::money]), (array[300::money])) _(x);
x
-----------
{$100.00}
{$200.00}
{$300.00}
(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(100::money)), (row(200::money))) _(x) union select x from (values (row(100::money)), (row(300::money))) _(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(100::money)), (row(200::money))) _(x) union select x from (values (row(100::money)), (row(300::money))) _(x);
x
-----------
($100.00)
($200.00)
($300.00)
(3 rows)
-- With a defined row type, the typcache can inspect the type's fields
-- for hashability.
create type ct1 as (f1 money);
explain (costs off)
select x from (values (row(100::money)::ct1), (row(200::money)::ct1)) _(x) union select x from (values (row(100::money)::ct1), (row(300::money)::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(100::money)::ct1), (row(200::money)::ct1)) _(x) union select x from (values (row(100::money)::ct1), (row(300::money)::ct1)) _(x);
x
-----------
($100.00)
($200.00)
($300.00)
(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...
^
HINT: 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;
explain (costs off)
select from generate_series(1,5) union select from generate_series(1,3);
QUERY PLAN
----------------------------------------------------------------
HashAggregate
-> 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
----------------------------------------------------------------------
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 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)
-- 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)
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;
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;
QUERY PLAN
-----------------------------------------------------
Limit
-> Merge Append
Sort Key: ((t1.a || t1.b))
-> Index Scan using t1_ab_idx on t1
-> Index Scan using t1c_ab_idx on t1c t1_1
-> Index Scan using t2_pkey on t2
-> 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;
-- 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
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;
-- 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)
-- 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
-> ProjectSet
-> Result
-> Result
(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)
-- 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;
QUERY PLAN
----------------------------------------------------------
Unique
-> Merge Append
Sort Key: "*SELECT* 1".q1
-> Subquery Scan on "*SELECT* 1"
-> Unique
-> Sort
Sort Key: i81.q1, i81.q2
-> Seq Scan on int8_tbl i81
Filter: (q2 IS NOT NULL)
-> Subquery Scan on "*SELECT* 2"
-> Unique
-> Sort
Sort Key: i82.q1, i82.q2
-> Seq Scan on int8_tbl i82
Filter: (q2 IS NOT NULL)
(15 rows)
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;
QUERY PLAN
--------------------------------------------------------
Unique
-> Merge Append
Sort Key: "*SELECT* 1".q1
-> Subquery Scan on "*SELECT* 1"
-> Unique
-> Sort
Sort Key: i81.q1, i81.q2
-> Seq Scan on int8_tbl i81
Filter: ((- q1) = q2)
-> Subquery Scan on "*SELECT* 2"
-> Unique
-> Sort
Sort Key: i82.q1, i82.q2
-> Seq Scan on int8_tbl i82
Filter: ((- q1) = q2)
(15 rows)
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)
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