Add more tests for targetlist SRFs.

We're considering changing the implementation of targetlist SRFs
considerably, and a lot of the current behaviour isn't tested in our
regression tests. Thus it seems useful to increase coverage to avoid
accidental behaviour changes.

It's quite possible that some of the plans here will require adjustments
to avoid falling afoul of ordering differences (e.g. hashed group
bys). The buildfarm will tell us.

Reviewed-By: Tom Lane
Discussion: <20160827214829.zo2dfb5jaikii5nw@alap3.anarazel.de>

src/test/regress/expected/tsrf.out

+--
+-- tsrf - targetlist set returning function tests
+--
+-- simple srf
+SELECT generate_series(1, 3);
+ generate_series 
+-----------------
+               1
+               2
+               3
+(3 rows)
+
+-- parallel iteration
+SELECT generate_series(1, 3), generate_series(3,5);
+ generate_series | generate_series 
+-----------------+-----------------
+               1 |               3
+               2 |               4
+               3 |               5
+(3 rows)
+
+-- parallel iteration, different number of rows
+SELECT generate_series(1, 2), generate_series(1,4);
+ generate_series | generate_series 
+-----------------+-----------------
+               1 |               1
+               2 |               2
+               1 |               3
+               2 |               4
+(4 rows)
+
+-- srf, with SRF argument
+SELECT generate_series(1, generate_series(1, 3));
+ generate_series 
+-----------------
+               1
+               1
+               2
+               1
+               2
+               3
+(6 rows)
+
+-- srf, with two SRF arguments
+SELECT generate_series(generate_series(1,3), generate_series(2, 4));
+ERROR:  functions and operators can take at most one set argument
+CREATE TABLE few(id int, dataa text, datab text);
+INSERT INTO few VALUES(1, 'a', 'foo'),(2, 'a', 'bar'),(3, 'b', 'bar');
+-- SRF output order of sorting is maintained, if SRF is not referenced
+SELECT few.id, generate_series(1,3) g FROM few ORDER BY id DESC;
+ id | g 
+----+---
+  3 | 1
+  3 | 2
+  3 | 3
+  2 | 1
+  2 | 2
+  2 | 3
+  1 | 1
+  1 | 2
+  1 | 3
+(9 rows)
+
+-- but SRFs can be referenced in sort
+SELECT few.id, generate_series(1,3) g FROM few ORDER BY id, g DESC;
+ id | g 
+----+---
+  1 | 3
+  1 | 2
+  1 | 1
+  2 | 3
+  2 | 2
+  2 | 1
+  3 | 3
+  3 | 2
+  3 | 1
+(9 rows)
+
+SELECT few.id, generate_series(1,3) g FROM few ORDER BY id, generate_series(1,3) DESC;
+ id | g 
+----+---
+  1 | 3
+  1 | 2
+  1 | 1
+  2 | 3
+  2 | 2
+  2 | 1
+  3 | 3
+  3 | 2
+  3 | 1
+(9 rows)
+
+-- it's weird to have ORDER BYs that increase the number of results
+SELECT few.id FROM few ORDER BY id, generate_series(1,3) DESC;
+ id 
+----
+  1
+  1
+  1
+  2
+  2
+  2
+  3
+  3
+  3
+(9 rows)
+
+-- SRFs are computed after aggregation
+SELECT few.dataa, count(*), min(id), max(id), unnest('{1,1,3}'::int[]) FROM few WHERE few.id = 1 GROUP BY few.dataa;
+ dataa | count | min | max | unnest 
+-------+-------+-----+-----+--------
+ a     |     1 |   1 |   1 |      1
+ a     |     1 |   1 |   1 |      1
+ a     |     1 |   1 |   1 |      3
+(3 rows)
+
+-- unless referenced in GROUP BY clause
+SELECT few.dataa, count(*), min(id), max(id), unnest('{1,1,3}'::int[]) FROM few WHERE few.id = 1 GROUP BY few.dataa, unnest('{1,1,3}'::int[]);
+ dataa | count | min | max | unnest 
+-------+-------+-----+-----+--------
+ a     |     2 |   1 |   1 |      1
+ a     |     1 |   1 |   1 |      3
+(2 rows)
+
+SELECT few.dataa, count(*), min(id), max(id), unnest('{1,1,3}'::int[]) FROM few WHERE few.id = 1 GROUP BY few.dataa, 5;
+ dataa | count | min | max | unnest 
+-------+-------+-----+-----+--------
+ a     |     2 |   1 |   1 |      1
+ a     |     1 |   1 |   1 |      3
+(2 rows)
+
+-- check HAVING works when GROUP BY does [not] reference SRF output
+SELECT dataa, generate_series(1,3), count(*) FROM few GROUP BY 1 HAVING count(*) > 1;
+ dataa | generate_series | count 
+-------+-----------------+-------
+ a     |               1 |     2
+ a     |               2 |     2
+ a     |               3 |     2
+(3 rows)
+
+SELECT dataa, generate_series(1,3), count(*) FROM few GROUP BY 1, 2 HAVING count(*) > 1;
+ dataa | generate_series | count 
+-------+-----------------+-------
+ a     |               1 |     2
+ a     |               2 |     2
+ a     |               3 |     2
+(3 rows)
+
+-- it's weird to have GROUP BYs that increase the number of results
+SELECT few.dataa, count(*), min(id), max(id) FROM few GROUP BY few.dataa;
+ dataa | count | min | max 
+-------+-------+-----+-----
+ b     |     1 |   3 |   3
+ a     |     2 |   1 |   2
+(2 rows)
+
+SELECT few.dataa, count(*), min(id), max(id) FROM few GROUP BY few.dataa, unnest('{1,1,3}'::int[]);
+ dataa | count | min | max 
+-------+-------+-----+-----
+ b     |     2 |   3 |   3
+ a     |     4 |   1 |   2
+ b     |     1 |   3 |   3
+ a     |     2 |   1 |   2
+(4 rows)
+
+-- SRFs are not allowed in aggregate arguments
+SELECT min(generate_series(1, 3)) FROM few;
+ERROR:  set-valued function called in context that cannot accept a set
+-- SRFs are normally computed after window functions
+SELECT id,lag(id) OVER(), count(*) OVER(), generate_series(1,3) FROM few;
+ id | lag | count | generate_series 
+----+-----+-------+-----------------
+  1 |     |     3 |               1
+  1 |     |     3 |               2
+  1 |     |     3 |               3
+  2 |   1 |     3 |               1
+  2 |   1 |     3 |               2
+  2 |   1 |     3 |               3
+  3 |   2 |     3 |               1
+  3 |   2 |     3 |               2
+  3 |   2 |     3 |               3
+(9 rows)
+
+-- unless referencing SRFs
+SELECT SUM(count(*)) OVER(PARTITION BY generate_series(1,3) ORDER BY generate_series(1,3)), generate_series(1,3) g FROM few GROUP BY g;
+ sum | g 
+-----+---
+   3 | 1
+   3 | 2
+   3 | 3
+(3 rows)
+
+-- sorting + grouping
+SELECT few.dataa, count(*), min(id), max(id), generate_series(1,3) FROM few GROUP BY few.dataa ORDER BY 5;
+ dataa | count | min | max | generate_series 
+-------+-------+-----+-----+-----------------
+ b     |     1 |   3 |   3 |               1
+ a     |     2 |   1 |   2 |               1
+ b     |     1 |   3 |   3 |               2
+ a     |     2 |   1 |   2 |               2
+ b     |     1 |   3 |   3 |               3
+ a     |     2 |   1 |   2 |               3
+(6 rows)
+
+-- grouping sets are a bit special, they produce NULLs in columns not actually NULL
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab);
+ dataa |  b  | g | count 
+-------+-----+---+-------
+ a     | bar | 1 |     1
+ a     | bar | 2 |     1
+ a     | foo | 1 |     1
+ a     | foo | 2 |     1
+ a     |     | 1 |     2
+ a     |     | 2 |     2
+ b     | bar | 1 |     1
+ b     | bar | 2 |     1
+ b     |     | 1 |     1
+ b     |     | 2 |     1
+       |     | 1 |     3
+       |     | 2 |     3
+       | bar | 1 |     2
+       | bar | 2 |     2
+       | foo | 1 |     1
+       | foo | 2 |     1
+(16 rows)
+
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab) ORDER BY dataa;
+ dataa |  b  | g | count 
+-------+-----+---+-------
+ a     | bar | 1 |     1
+ a     | bar | 2 |     1
+ a     | foo | 1 |     1
+ a     | foo | 2 |     1
+ a     |     | 1 |     2
+ a     |     | 2 |     2
+ b     | bar | 1 |     1
+ b     | bar | 2 |     1
+ b     |     | 1 |     1
+ b     |     | 2 |     1
+       |     | 1 |     3
+       |     | 2 |     3
+       | bar | 1 |     2
+       | bar | 2 |     2
+       | foo | 1 |     1
+       | foo | 2 |     1
+(16 rows)
+
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab) ORDER BY g;
+ dataa |  b  | g | count 
+-------+-----+---+-------
+ a     | bar | 1 |     1
+ a     | foo | 1 |     1
+ a     |     | 1 |     2
+ b     | bar | 1 |     1
+ b     |     | 1 |     1
+       |     | 1 |     3
+       | bar | 1 |     2
+       | foo | 1 |     1
+       | foo | 2 |     1
+ a     | bar | 2 |     1
+ b     |     | 2 |     1
+ a     | foo | 2 |     1
+       | bar | 2 |     2
+ a     |     | 2 |     2
+       |     | 2 |     3
+ b     | bar | 2 |     1
+(16 rows)
+
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab, g);
+ dataa |  b  | g | count 
+-------+-----+---+-------
+ a     | bar | 1 |     1
+ a     | bar | 2 |     1
+ a     | bar |   |     2
+ a     | foo | 1 |     1
+ a     | foo | 2 |     1
+ a     | foo |   |     2
+ a     |     |   |     4
+ b     | bar | 1 |     1
+ b     | bar | 2 |     1
+ b     | bar |   |     2
+ b     |     |   |     2
+       |     |   |     6
+ a     |     | 1 |     2
+ b     |     | 1 |     1
+       |     | 1 |     3
+ a     |     | 2 |     2
+ b     |     | 2 |     1
+       |     | 2 |     3
+       | bar | 1 |     2
+       | bar | 2 |     2
+       | bar |   |     4
+       | foo | 1 |     1
+       | foo | 2 |     1
+       | foo |   |     2
+(24 rows)
+
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab, g) ORDER BY dataa;
+ dataa |  b  | g | count 
+-------+-----+---+-------
+ a     | bar | 1 |     1
+ a     | bar | 2 |     1
+ a     | bar |   |     2
+ a     | foo | 1 |     1
+ a     | foo | 2 |     1
+ a     | foo |   |     2
+ a     |     |   |     4
+ a     |     | 1 |     2
+ a     |     | 2 |     2
+ b     | bar | 2 |     1
+ b     |     |   |     2
+ b     |     | 1 |     1
+ b     |     | 2 |     1
+ b     | bar | 1 |     1
+ b     | bar |   |     2
+       | foo |   |     2
+       | foo | 1 |     1
+       |     | 2 |     3
+       | bar | 1 |     2
+       | bar | 2 |     2
+       |     |   |     6
+       | foo | 2 |     1
+       | bar |   |     4
+       |     | 1 |     3
+(24 rows)
+
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab, g) ORDER BY g;
+ dataa |  b  | g | count 
+-------+-----+---+-------
+ a     | bar | 1 |     1
+ a     | foo | 1 |     1
+ b     | bar | 1 |     1
+ a     |     | 1 |     2
+ b     |     | 1 |     1
+       |     | 1 |     3
+       | bar | 1 |     2
+       | foo | 1 |     1
+       | foo | 2 |     1
+       | bar | 2 |     2
+ a     |     | 2 |     2
+ b     |     | 2 |     1
+ a     | bar | 2 |     1
+       |     | 2 |     3
+ a     | foo | 2 |     1
+ b     | bar | 2 |     1
+ a     | foo |   |     2
+ b     | bar |   |     2
+ b     |     |   |     2
+       |     |   |     6
+ a     |     |   |     4
+       | bar |   |     4
+       | foo |   |     2
+ a     | bar |   |     2
+(24 rows)
+
+-- data modification
+CREATE TABLE fewmore AS SELECT generate_series(1,3) AS data;
+INSERT INTO fewmore VALUES(generate_series(4,5));
+SELECT * FROM fewmore;
+ data 
+------
+    1
+    2
+    3
+    4
+    5
+(5 rows)
+
+-- nonsense that seems to be allowed
+UPDATE fewmore SET data = generate_series(4,9);
+-- SRFs are not allowed in RETURNING
+INSERT INTO fewmore VALUES(1) RETURNING generate_series(1,3);
+ERROR:  set-valued function called in context that cannot accept a set
+-- nor aggregate arguments
+SELECT count(generate_series(1,3)) FROM few;
+ERROR:  set-valued function called in context that cannot accept a set
+-- nor proper VALUES
+VALUES(1, generate_series(1,2));
+ERROR:  set-valued function called in context that cannot accept a set
+-- DISTINCT ON is evaluated before tSRF evaluation if SRF is not
+-- referenced either in ORDER BY or in the DISTINCT ON list. The ORDER
+-- BY reference can be implicitly generated, if there's no other ORDER BY.
+-- implicit reference (via implicit ORDER) to all columns
+SELECT DISTINCT ON (a) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b);
+ a | b | g 
+---+---+---
+ 1 | 1 | 1
+ 3 | 2 | 1
+ 5 | 3 | 1
+(3 rows)
+
+-- unreferenced in DISTINCT ON or ORDER BY
+SELECT DISTINCT ON (a) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b)
+ORDER BY a, b DESC;
+ a | b | g 
+---+---+---
+ 1 | 4 | 1
+ 1 | 4 | 2
+ 1 | 4 | 3
+ 3 | 2 | 1
+ 3 | 2 | 2
+ 3 | 2 | 3
+ 5 | 3 | 1
+ 5 | 3 | 2
+ 5 | 3 | 3
+(9 rows)
+
+-- referenced in ORDER BY
+SELECT DISTINCT ON (a) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b)
+ORDER BY a, b DESC, g DESC;
+ a | b | g 
+---+---+---
+ 1 | 4 | 3
+ 3 | 2 | 3
+ 5 | 3 | 3
+(3 rows)
+
+-- referenced in ORDER BY and DISTINCT ON
+SELECT DISTINCT ON (a, b, g) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b)
+ORDER BY a, b DESC, g DESC;
+ a | b | g 
+---+---+---
+ 1 | 4 | 3
+ 1 | 4 | 2
+ 1 | 4 | 1
+ 1 | 1 | 3
+ 1 | 1 | 2
+ 1 | 1 | 1
+ 3 | 2 | 3
+ 3 | 2 | 2
+ 3 | 2 | 1
+ 3 | 1 | 3
+ 3 | 1 | 2
+ 3 | 1 | 1
+ 5 | 3 | 3
+ 5 | 3 | 2
+ 5 | 3 | 1
+ 5 | 1 | 3
+ 5 | 1 | 2
+ 5 | 1 | 1
+(18 rows)
+
+-- only SRF mentioned in DISTINCT ON
+SELECT DISTINCT ON (g) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b);
+ a | b | g 
+---+---+---
+ 3 | 2 | 1
+ 5 | 1 | 2
+ 3 | 1 | 3
+(3 rows)
+
+-- LIMIT / OFFSET is evaluated after SRF evaluation
+SELECT a, generate_series(1,2) FROM (VALUES(1),(2),(3)) r(a) LIMIT 2 OFFSET 2;
+ a | generate_series 
+---+-----------------
+ 2 |               1
+ 2 |               2
+(2 rows)
+
+-- SRFs are not allowed in LIMIT.
+SELECT 1 LIMIT generate_series(1,3);
+ERROR:  argument of LIMIT must not return a set
+LINE 1: SELECT 1 LIMIT generate_series(1,3);
+                       ^
+-- tSRF in correlated subquery, referencing table outside
+SELECT (SELECT generate_series(1,3) LIMIT 1 OFFSET few.id) FROM few;
+ generate_series 
+-----------------
+               2
+               3
+                
+(3 rows)
+
+-- tSRF in correlated subquery, referencing SRF outside
+SELECT (SELECT generate_series(1,3) LIMIT 1 OFFSET g.i) FROM generate_series(0,3) g(i);
+ generate_series 
+-----------------
+               1
+               2
+               3
+                
+(4 rows)
+
+-- Operators can return sets too
+CREATE OPERATOR |@| (PROCEDURE = unnest, RIGHTARG = ANYARRAY);
+SELECT |@|ARRAY[1,2,3];
+ ?column? 
+----------
+        1
+        2
+        3
+(3 rows)
+
+-- Clean up
+DROP TABLE few;
+DROP TABLE fewmore;

src/test/regress/parallel_schedule

@@ -89,7 +89,7 @@ test: brin gin gist spgist privileges init_privs security_label collate matview
 # ----------
 # Another group of parallel tests
 # ----------
-test: alter_generic alter_operator misc psql async dbsize misc_functions
+test: alter_generic alter_operator misc psql async dbsize misc_functions tsrf
 
 # rules cannot run concurrently with any test that creates a view
 test: rules psql_crosstab amutils

src/test/regress/serial_schedule

@@ -123,6 +123,7 @@ test: psql
 test: async
 test: dbsize
 test: misc_functions
+test: tsrf
 test: rules
 test: psql_crosstab
 test: select_parallel

src/test/regress/sql/tsrf.sql

+--
+-- tsrf - targetlist set returning function tests
+--
+
+-- simple srf
+SELECT generate_series(1, 3);
+
+-- parallel iteration
+SELECT generate_series(1, 3), generate_series(3,5);
+
+-- parallel iteration, different number of rows
+SELECT generate_series(1, 2), generate_series(1,4);
+
+-- srf, with SRF argument
+SELECT generate_series(1, generate_series(1, 3));
+
+-- srf, with two SRF arguments
+SELECT generate_series(generate_series(1,3), generate_series(2, 4));
+
+CREATE TABLE few(id int, dataa text, datab text);
+INSERT INTO few VALUES(1, 'a', 'foo'),(2, 'a', 'bar'),(3, 'b', 'bar');
+
+-- SRF output order of sorting is maintained, if SRF is not referenced
+SELECT few.id, generate_series(1,3) g FROM few ORDER BY id DESC;
+
+-- but SRFs can be referenced in sort
+SELECT few.id, generate_series(1,3) g FROM few ORDER BY id, g DESC;
+SELECT few.id, generate_series(1,3) g FROM few ORDER BY id, generate_series(1,3) DESC;
+
+-- it's weird to have ORDER BYs that increase the number of results
+SELECT few.id FROM few ORDER BY id, generate_series(1,3) DESC;
+
+-- SRFs are computed after aggregation
+SELECT few.dataa, count(*), min(id), max(id), unnest('{1,1,3}'::int[]) FROM few WHERE few.id = 1 GROUP BY few.dataa;
+-- unless referenced in GROUP BY clause
+SELECT few.dataa, count(*), min(id), max(id), unnest('{1,1,3}'::int[]) FROM few WHERE few.id = 1 GROUP BY few.dataa, unnest('{1,1,3}'::int[]);
+SELECT few.dataa, count(*), min(id), max(id), unnest('{1,1,3}'::int[]) FROM few WHERE few.id = 1 GROUP BY few.dataa, 5;
+
+-- check HAVING works when GROUP BY does [not] reference SRF output
+SELECT dataa, generate_series(1,3), count(*) FROM few GROUP BY 1 HAVING count(*) > 1;
+SELECT dataa, generate_series(1,3), count(*) FROM few GROUP BY 1, 2 HAVING count(*) > 1;
+
+-- it's weird to have GROUP BYs that increase the number of results
+SELECT few.dataa, count(*), min(id), max(id) FROM few GROUP BY few.dataa;
+SELECT few.dataa, count(*), min(id), max(id) FROM few GROUP BY few.dataa, unnest('{1,1,3}'::int[]);
+
+-- SRFs are not allowed in aggregate arguments
+SELECT min(generate_series(1, 3)) FROM few;
+
+-- SRFs are normally computed after window functions
+SELECT id,lag(id) OVER(), count(*) OVER(), generate_series(1,3) FROM few;
+-- unless referencing SRFs
+SELECT SUM(count(*)) OVER(PARTITION BY generate_series(1,3) ORDER BY generate_series(1,3)), generate_series(1,3) g FROM few GROUP BY g;
+
+-- sorting + grouping
+SELECT few.dataa, count(*), min(id), max(id), generate_series(1,3) FROM few GROUP BY few.dataa ORDER BY 5;
+
+-- grouping sets are a bit special, they produce NULLs in columns not actually NULL
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab);
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab) ORDER BY dataa;
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab) ORDER BY g;
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab, g);
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab, g) ORDER BY dataa;
+SELECT dataa, datab b, generate_series(1,2) g, count(*) FROM few GROUP BY CUBE(dataa, datab, g) ORDER BY g;
+
+-- data modification
+CREATE TABLE fewmore AS SELECT generate_series(1,3) AS data;
+INSERT INTO fewmore VALUES(generate_series(4,5));
+SELECT * FROM fewmore;
+
+-- nonsense that seems to be allowed
+UPDATE fewmore SET data = generate_series(4,9);
+
+-- SRFs are not allowed in RETURNING
+INSERT INTO fewmore VALUES(1) RETURNING generate_series(1,3);
+-- nor aggregate arguments
+SELECT count(generate_series(1,3)) FROM few;
+-- nor proper VALUES
+VALUES(1, generate_series(1,2));
+
+-- DISTINCT ON is evaluated before tSRF evaluation if SRF is not
+-- referenced either in ORDER BY or in the DISTINCT ON list. The ORDER
+-- BY reference can be implicitly generated, if there's no other ORDER BY.
+
+-- implicit reference (via implicit ORDER) to all columns
+SELECT DISTINCT ON (a) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b);
+
+-- unreferenced in DISTINCT ON or ORDER BY
+SELECT DISTINCT ON (a) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b)
+ORDER BY a, b DESC;
+
+-- referenced in ORDER BY
+SELECT DISTINCT ON (a) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b)
+ORDER BY a, b DESC, g DESC;
+
+-- referenced in ORDER BY and DISTINCT ON
+SELECT DISTINCT ON (a, b, g) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b)
+ORDER BY a, b DESC, g DESC;
+
+-- only SRF mentioned in DISTINCT ON
+SELECT DISTINCT ON (g) a, b, generate_series(1,3) g
+FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b);
+
+-- LIMIT / OFFSET is evaluated after SRF evaluation
+SELECT a, generate_series(1,2) FROM (VALUES(1),(2),(3)) r(a) LIMIT 2 OFFSET 2;
+-- SRFs are not allowed in LIMIT.
+SELECT 1 LIMIT generate_series(1,3);
+
+-- tSRF in correlated subquery, referencing table outside
+SELECT (SELECT generate_series(1,3) LIMIT 1 OFFSET few.id) FROM few;
+-- tSRF in correlated subquery, referencing SRF outside
+SELECT (SELECT generate_series(1,3) LIMIT 1 OFFSET g.i) FROM generate_series(0,3) g(i);
+
+-- Operators can return sets too
+CREATE OPERATOR |@| (PROCEDURE = unnest, RIGHTARG = ANYARRAY);
+SELECT |@|ARRAY[1,2,3];
+
+-- Clean up
+DROP TABLE few;
+DROP TABLE fewmore;