Implement comparison of generic records (composite types), and invent a

pseudo-type record[] to represent arrays of possibly-anonymous composite
types.  Since composite datums carry their own type identification, no
extra knowledge is needed at the array level.

The main reason for doing this right now is that it is necessary to support
the general case of detection of cycles in recursive queries: if you need to
compare more than one column to detect a cycle, you need to compare a ROW()
to an array built from ROW()s, at least if you want to do it as the spec
suggests.  Add some documentation and regression tests concerning the cycle
detection issue.

4 files changed, 97 insertions, 0 deletions

diff --git a/src/test/regress/expected/rowtypes.out b/src/test/regress/expected/rowtypes.out
index 73ae3ce10ef..e1181a61b83 100644
--- a/src/test/regress/expected/rowtypes.out
+++ b/src/test/regress/expected/rowtypes.out
@@ -269,3 +269,23 @@ select ROW() = ROW();
 ERROR:  cannot compare rows of zero length
 LINE 1: select ROW() = ROW();
                      ^
+-- Check ability to create arrays of anonymous rowtypes
+select array[ row(1,2), row(3,4), row(5,6) ];
+           array           
+---------------------------
+ {"(1,2)","(3,4)","(5,6)"}
+(1 row)
+
+-- Check ability to compare an anonymous row to elements of an array
+select row(1,1.1) = any (array[ row(7,7.7), row(1,1.1), row(0,0.0) ]);
+ ?column? 
+----------
+ t
+(1 row)
+
+select row(1,1.1) = any (array[ row(7,7.7), row(1,1.0), row(0,0.0) ]);
+ ?column? 
+----------
+ f
+(1 row)
+
diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index fe7561065ed..e8d3e43b7b6 100644
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -452,6 +452,54 @@ SELECT t1.id, count(t2.*) FROM t AS t1 JOIN t AS t2 ON
 (2 rows)
 
 --
+-- test cycle detection
+--
+create temp table graph( f int, t int, label text );
+insert into graph values
+	(1, 2, 'arc 1 -> 2'),
+	(1, 3, 'arc 1 -> 3'),
+	(2, 3, 'arc 2 -> 3'),
+	(1, 4, 'arc 1 -> 4'),
+	(4, 5, 'arc 4 -> 5'),
+	(5, 1, 'arc 5 -> 1');
+with recursive search_graph(f, t, label, path, cycle) as (
+	select *, array[row(g.f, g.t)], false from graph g
+	union all
+	select g.*, path || array[row(g.f, g.t)], row(g.f, g.t) = any(path)
+	from graph g, search_graph sg
+	where g.f = sg.t and not cycle
+)
+select * from search_graph;
+ f | t |   label    |                   path                    | cycle 
+---+---+------------+-------------------------------------------+-------
+ 1 | 2 | arc 1 -> 2 | {"(1,2)"}                                 | f
+ 1 | 3 | arc 1 -> 3 | {"(1,3)"}                                 | f
+ 2 | 3 | arc 2 -> 3 | {"(2,3)"}                                 | f
+ 1 | 4 | arc 1 -> 4 | {"(1,4)"}                                 | f
+ 4 | 5 | arc 4 -> 5 | {"(4,5)"}                                 | f
+ 5 | 1 | arc 5 -> 1 | {"(5,1)"}                                 | f
+ 1 | 2 | arc 1 -> 2 | {"(5,1)","(1,2)"}                         | f
+ 1 | 3 | arc 1 -> 3 | {"(5,1)","(1,3)"}                         | f
+ 1 | 4 | arc 1 -> 4 | {"(5,1)","(1,4)"}                         | f
+ 2 | 3 | arc 2 -> 3 | {"(1,2)","(2,3)"}                         | f
+ 4 | 5 | arc 4 -> 5 | {"(1,4)","(4,5)"}                         | f
+ 5 | 1 | arc 5 -> 1 | {"(4,5)","(5,1)"}                         | f
+ 1 | 2 | arc 1 -> 2 | {"(4,5)","(5,1)","(1,2)"}                 | f
+ 1 | 3 | arc 1 -> 3 | {"(4,5)","(5,1)","(1,3)"}                 | f
+ 1 | 4 | arc 1 -> 4 | {"(4,5)","(5,1)","(1,4)"}                 | f
+ 2 | 3 | arc 2 -> 3 | {"(5,1)","(1,2)","(2,3)"}                 | f
+ 4 | 5 | arc 4 -> 5 | {"(5,1)","(1,4)","(4,5)"}                 | f
+ 5 | 1 | arc 5 -> 1 | {"(1,4)","(4,5)","(5,1)"}                 | f
+ 1 | 2 | arc 1 -> 2 | {"(1,4)","(4,5)","(5,1)","(1,2)"}         | f
+ 1 | 3 | arc 1 -> 3 | {"(1,4)","(4,5)","(5,1)","(1,3)"}         | f
+ 1 | 4 | arc 1 -> 4 | {"(1,4)","(4,5)","(5,1)","(1,4)"}         | t
+ 2 | 3 | arc 2 -> 3 | {"(4,5)","(5,1)","(1,2)","(2,3)"}         | f
+ 4 | 5 | arc 4 -> 5 | {"(4,5)","(5,1)","(1,4)","(4,5)"}         | t
+ 5 | 1 | arc 5 -> 1 | {"(5,1)","(1,4)","(4,5)","(5,1)"}         | t
+ 2 | 3 | arc 2 -> 3 | {"(1,4)","(4,5)","(5,1)","(1,2)","(2,3)"} | f
+(25 rows)
+
+--
 -- test multiple WITH queries
 --
 WITH RECURSIVE
diff --git a/src/test/regress/sql/rowtypes.sql b/src/test/regress/sql/rowtypes.sql
index 7e5c554d3b7..a8520c5bd2c 100644
--- a/src/test/regress/sql/rowtypes.sql
+++ b/src/test/regress/sql/rowtypes.sql
@@ -113,3 +113,10 @@ order by thousand, tenthous;
 select ROW();
 select ROW() IS NULL;
 select ROW() = ROW();
+
+-- Check ability to create arrays of anonymous rowtypes
+select array[ row(1,2), row(3,4), row(5,6) ];
+
+-- Check ability to compare an anonymous row to elements of an array
+select row(1,1.1) = any (array[ row(7,7.7), row(1,1.1), row(0,0.0) ]);
+select row(1,1.1) = any (array[ row(7,7.7), row(1,1.0), row(0,0.0) ]);
diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql
index 54d311101d1..d37f0d9723e 100644
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -251,6 +251,28 @@ SELECT t1.id, count(t2.*) FROM t AS t1 JOIN t AS t2 ON
 	ORDER BY t1.id;
 
 --
+-- test cycle detection
+--
+create temp table graph( f int, t int, label text );
+
+insert into graph values
+	(1, 2, 'arc 1 -> 2'),
+	(1, 3, 'arc 1 -> 3'),
+	(2, 3, 'arc 2 -> 3'),
+	(1, 4, 'arc 1 -> 4'),
+	(4, 5, 'arc 4 -> 5'),
+	(5, 1, 'arc 5 -> 1');
+
+with recursive search_graph(f, t, label, path, cycle) as (
+	select *, array[row(g.f, g.t)], false from graph g
+	union all
+	select g.*, path || array[row(g.f, g.t)], row(g.f, g.t) = any(path)
+	from graph g, search_graph sg
+	where g.f = sg.t and not cycle
+)
+select * from search_graph;
+
+--
 -- test multiple WITH queries
 --
 WITH RECURSIVE