Enhanced cycle mark values

Per SQL:202x draft, in the CYCLE clause of a recursive query, the
cycle mark values can be of type boolean and can be omitted, in which
case they default to TRUE and FALSE.

Reviewed-by: Vik Fearing <vik@postgresfriends.org>
Discussion: https://www.postgresql.org/message-id/flat/db80ceee-6f97-9b4a-8ee8-3ba0c58e5be2@2ndquadrant.com

doc/src/sgml/queries.sgml

@@ -2349,14 +2349,13 @@ WITH RECURSIVE search_graph(id, link, data, depth) AS (
     SELECT g.id, g.link, g.data, sg.depth + 1
     FROM graph g, search_graph sg
     WHERE g.id = sg.link
-) <emphasis>CYCLE id SET is_cycle TO true DEFAULT false USING path</emphasis>
+) <emphasis>CYCLE id SET is_cycle USING path</emphasis>
 SELECT * FROM search_graph;
 </programlisting>
    and it will be internally rewritten to the above form.  The
    <literal>CYCLE</literal> clause specifies first the list of columns to
    track for cycle detection, then a column name that will show whether a
-   cycle has been detected, then two values to use in that column for the yes
-   and no cases, and finally the name of another column that will track the
+   cycle has been detected, and finally the name of another column that will track the
    path.  The cycle and path columns will implicitly be added to the output
    rows of the CTE.
   </para>

doc/src/sgml/ref/select.sgml

@@ -74,7 +74,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
     <replaceable class="parameter">with_query_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ] AS [ [ NOT ] MATERIALIZED ] ( <replaceable class="parameter">select</replaceable> | <replaceable class="parameter">values</replaceable> | <replaceable class="parameter">insert</replaceable> | <replaceable class="parameter">update</replaceable> | <replaceable class="parameter">delete</replaceable> )
         [ SEARCH { BREADTH | DEPTH } FIRST BY <replaceable>column_name</replaceable> [, ...] SET <replaceable>search_seq_col_name</replaceable> ]
-        [ CYCLE <replaceable>column_name</replaceable> [, ...] SET <replaceable>cycle_mark_col_name</replaceable> TO <replaceable>cycle_mark_value</replaceable> DEFAULT <replaceable>cycle_mark_default</replaceable> USING <replaceable>cycle_path_col_name</replaceable> ]
+        [ CYCLE <replaceable>column_name</replaceable> [, ...] SET <replaceable>cycle_mark_col_name</replaceable> [ TO <replaceable>cycle_mark_value</replaceable> DEFAULT <replaceable>cycle_mark_default</replaceable> ] USING <replaceable>cycle_path_col_name</replaceable> ]
 
 TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
 </synopsis>
@@ -302,8 +302,10 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
     been detected.  <replaceable>cycle_mark_value</replaceable> and
     <replaceable>cycle_mark_default</replaceable> must be constants and they
     must be coercible to a common data type, and the data type must have an
-    inequality operator.  (The SQL standard requires that they be character
-    strings, but PostgreSQL does not require that.)  Furthermore, a column
+    inequality operator.  (The SQL standard requires that they be Boolean
+    constants or character strings, but PostgreSQL does not require that.)  By
+    default, <literal>TRUE</literal> and <literal>FALSE</literal> (of type
+    <type>boolean</type>) are used.  Furthermore, a column
     named <replaceable>cycle_path_col_name</replaceable> will be added to the
     result column list of the <literal>WITH</literal> query.  This column is
     used internally for tracking visited rows.  See <xref

src/backend/catalog/sql_features.txt

@@ -425,6 +425,7 @@ T121	WITH (excluding RECURSIVE) in query expression			YES
 T122	WITH (excluding RECURSIVE) in subquery			YES	
 T131	Recursive query			YES	
 T132	Recursive query in subquery			YES	
+T133	Enhanced cycle mark values			YES	SQL:202x draft
 T141	SIMILAR predicate			YES	
 T151	DISTINCT predicate			YES	
 T152	DISTINCT predicate with negation			YES	

src/backend/parser/gram.y

@@ -11442,6 +11442,17 @@ opt_cycle_clause:
 				n->location = @1;
 				$$ = (Node *) n;
 			}
+		| CYCLE columnList SET ColId USING ColId
+			{
+				CTECycleClause *n = makeNode(CTECycleClause);
+				n->cycle_col_list = $2;
+				n->cycle_mark_column = $4;
+				n->cycle_mark_value = makeBoolAConst(true, -1);
+				n->cycle_mark_default = makeBoolAConst(false, -1);
+				n->cycle_path_column = $6;
+				n->location = @1;
+				$$ = (Node *) n;
+			}
 		| /*EMPTY*/
 			{
 				$$ = NULL;

src/backend/utils/adt/ruleutils.c

@@ -5208,10 +5208,21 @@ get_with_clause(Query *query, deparse_context *context)
 			}
 
 			appendStringInfo(buf, " SET %s", quote_identifier(cte->cycle_clause->cycle_mark_column));
-			appendStringInfoString(buf, " TO ");
-			get_rule_expr(cte->cycle_clause->cycle_mark_value, context, false);
-			appendStringInfoString(buf, " DEFAULT ");
-			get_rule_expr(cte->cycle_clause->cycle_mark_default, context, false);
+
+			{
+				Const	   *cmv = castNode(Const, cte->cycle_clause->cycle_mark_value);
+				Const	   *cmd = castNode(Const, cte->cycle_clause->cycle_mark_default);
+
+				if (!(cmv->consttype == BOOLOID && !cmv->constisnull && DatumGetBool(cmv->constvalue) == true &&
+					  cmd->consttype == BOOLOID && !cmd->constisnull && DatumGetBool(cmd->constvalue) == false))
+				{
+					appendStringInfoString(buf, " TO ");
+					get_rule_expr(cte->cycle_clause->cycle_mark_value, context, false);
+					appendStringInfoString(buf, " DEFAULT ");
+					get_rule_expr(cte->cycle_clause->cycle_mark_default, context, false);
+				}
+			}
+
 			appendStringInfo(buf, " USING %s", quote_identifier(cte->cycle_clause->cycle_path_column));
 		}
 

src/test/regress/expected/with.out

@@ -951,7 +951,7 @@ with recursive search_graph(f, t, label) as (
 	select g.*
 	from graph g, search_graph sg
 	where g.f = sg.t
-) cycle f, t set is_cycle to true default false using path
+) cycle f, t set is_cycle using path
 select * from search_graph;
  f | t |   label    | is_cycle |                   path                    
 ---+---+------------+----------+-------------------------------------------
@@ -1071,7 +1071,7 @@ with recursive a as (
 	select 1 as b
 	union all
 	select * from a
-) cycle b set c to true default false using p
+) cycle b set c using p
 select * from a;
  b | c |     p     
 ---+---+-----------
@@ -1087,7 +1087,7 @@ with recursive search_graph(f, t, label) as (
 	from graph g, search_graph sg
 	where g.f = sg.t
 ) search depth first by f, t set seq
-  cycle f, t set is_cycle to true default false using path
+  cycle f, t set is_cycle using path
 select * from search_graph;
  f | t |   label    |                    seq                    | is_cycle |                   path                    
 ---+---+------------+-------------------------------------------+----------+-------------------------------------------
@@ -1125,7 +1125,7 @@ with recursive search_graph(f, t, label) as (
 	from graph g, search_graph sg
 	where g.f = sg.t
 ) search breadth first by f, t set seq
-  cycle f, t set is_cycle to true default false using path
+  cycle f, t set is_cycle using path
 select * from search_graph;
  f | t |   label    |   seq   | is_cycle |                   path                    
 ---+---+------------+---------+----------+-------------------------------------------
@@ -1163,10 +1163,10 @@ with recursive search_graph(f, t, label) as (
 	select g.*
 	from graph g, search_graph sg
 	where g.f = sg.t
-) cycle foo, tar set is_cycle to true default false using path
+) cycle foo, tar set is_cycle using path
 select * from search_graph;
 ERROR:  cycle column "foo" not in WITH query column list
-LINE 7: ) cycle foo, tar set is_cycle to true default false using pa...
+LINE 7: ) cycle foo, tar set is_cycle using path
           ^
 with recursive search_graph(f, t, label) as (
 	select * from graph g
@@ -1257,38 +1257,99 @@ ERROR:  search_sequence column name and cycle path column name are the same
 LINE 7: ) search depth first by f, t set foo
           ^
 -- test ruleutils and view expansion
-create temp view v_cycle as
+create temp view v_cycle1 as
 with recursive search_graph(f, t, label) as (
 	select * from graph g
 	union all
 	select g.*
 	from graph g, search_graph sg
 	where g.f = sg.t
-) cycle f, t set is_cycle to true default false using path
+) cycle f, t set is_cycle using path
 select f, t, label from search_graph;
-select pg_get_viewdef('v_cycle');
-                           pg_get_viewdef                           
---------------------------------------------------------------------
-  WITH RECURSIVE search_graph(f, t, label) AS (                    +
-          SELECT g.f,                                              +
-             g.t,                                                  +
-             g.label                                               +
-            FROM graph g                                           +
-         UNION ALL                                                 +
-          SELECT g.f,                                              +
-             g.t,                                                  +
-             g.label                                               +
-            FROM graph g,                                          +
-             search_graph sg                                       +
-           WHERE (g.f = sg.t)                                      +
-         ) CYCLE f, t SET is_cycle TO true DEFAULT false USING path+
-  SELECT search_graph.f,                                           +
-     search_graph.t,                                               +
-     search_graph.label                                            +
+create temp view v_cycle2 as
+with recursive search_graph(f, t, label) as (
+	select * from graph g
+	union all
+	select g.*
+	from graph g, search_graph sg
+	where g.f = sg.t
+) cycle f, t set is_cycle to 'Y' default 'N' using path
+select f, t, label from search_graph;
+select pg_get_viewdef('v_cycle1');
+                 pg_get_viewdef                 
+------------------------------------------------
+  WITH RECURSIVE search_graph(f, t, label) AS (+
+          SELECT g.f,                          +
+             g.t,                              +
+             g.label                           +
+            FROM graph g                       +
+         UNION ALL                             +
+          SELECT g.f,                          +
+             g.t,                              +
+             g.label                           +
+            FROM graph g,                      +
+             search_graph sg                   +
+           WHERE (g.f = sg.t)                  +
+         ) CYCLE f, t SET is_cycle USING path  +
+  SELECT search_graph.f,                       +
+     search_graph.t,                           +
+     search_graph.label                        +
     FROM search_graph;
 (1 row)
 
-select * from v_cycle;
+select pg_get_viewdef('v_cycle2');
+                               pg_get_viewdef                                
+-----------------------------------------------------------------------------
+  WITH RECURSIVE search_graph(f, t, label) AS (                             +
+          SELECT g.f,                                                       +
+             g.t,                                                           +
+             g.label                                                        +
+            FROM graph g                                                    +
+         UNION ALL                                                          +
+          SELECT g.f,                                                       +
+             g.t,                                                           +
+             g.label                                                        +
+            FROM graph g,                                                   +
+             search_graph sg                                                +
+           WHERE (g.f = sg.t)                                               +
+         ) CYCLE f, t SET is_cycle TO 'Y'::text DEFAULT 'N'::text USING path+
+  SELECT search_graph.f,                                                    +
+     search_graph.t,                                                        +
+     search_graph.label                                                     +
+    FROM search_graph;
+(1 row)
+
+select * from v_cycle1;
+ f | t |   label    
+---+---+------------
+ 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
+ 1 | 2 | arc 1 -> 2
+ 1 | 3 | arc 1 -> 3
+ 1 | 4 | arc 1 -> 4
+ 2 | 3 | arc 2 -> 3
+ 4 | 5 | arc 4 -> 5
+ 5 | 1 | arc 5 -> 1
+ 1 | 2 | arc 1 -> 2
+ 1 | 3 | arc 1 -> 3
+ 1 | 4 | arc 1 -> 4
+ 2 | 3 | arc 2 -> 3
+ 4 | 5 | arc 4 -> 5
+ 5 | 1 | arc 5 -> 1
+ 1 | 2 | arc 1 -> 2
+ 1 | 3 | arc 1 -> 3
+ 1 | 4 | arc 1 -> 4
+ 2 | 3 | arc 2 -> 3
+ 4 | 5 | arc 4 -> 5
+ 5 | 1 | arc 5 -> 1
+ 2 | 3 | arc 2 -> 3
+(25 rows)
+
+select * from v_cycle2;
  f | t |   label    
 ---+---+------------
  1 | 2 | arc 1 -> 2

src/test/regress/sql/with.sql

@@ -509,7 +509,7 @@ with recursive search_graph(f, t, label) as (
 	select g.*
 	from graph g, search_graph sg
 	where g.f = sg.t
-) cycle f, t set is_cycle to true default false using path
+) cycle f, t set is_cycle using path
 select * from search_graph;
 
 with recursive search_graph(f, t, label) as (
@@ -545,7 +545,7 @@ with recursive a as (
 	select 1 as b
 	union all
 	select * from a
-) cycle b set c to true default false using p
+) cycle b set c using p
 select * from a;
 
 -- search+cycle
@@ -556,7 +556,7 @@ with recursive search_graph(f, t, label) as (
 	from graph g, search_graph sg
 	where g.f = sg.t
 ) search depth first by f, t set seq
-  cycle f, t set is_cycle to true default false using path
+  cycle f, t set is_cycle using path
 select * from search_graph;
 
 with recursive search_graph(f, t, label) as (
@@ -566,7 +566,7 @@ with recursive search_graph(f, t, label) as (
 	from graph g, search_graph sg
 	where g.f = sg.t
 ) search breadth first by f, t set seq
-  cycle f, t set is_cycle to true default false using path
+  cycle f, t set is_cycle using path
 select * from search_graph;
 
 -- various syntax errors
@@ -576,7 +576,7 @@ with recursive search_graph(f, t, label) as (
 	select g.*
 	from graph g, search_graph sg
 	where g.f = sg.t
-) cycle foo, tar set is_cycle to true default false using path
+) cycle foo, tar set is_cycle using path
 select * from search_graph;
 
 with recursive search_graph(f, t, label) as (
@@ -654,19 +654,31 @@ with recursive search_graph(f, t, label) as (
 select * from search_graph;
 
 -- test ruleutils and view expansion
-create temp view v_cycle as
+create temp view v_cycle1 as
 with recursive search_graph(f, t, label) as (
 	select * from graph g
 	union all
 	select g.*
 	from graph g, search_graph sg
 	where g.f = sg.t
-) cycle f, t set is_cycle to true default false using path
+) cycle f, t set is_cycle using path
+select f, t, label from search_graph;
+
+create temp view v_cycle2 as
+with recursive search_graph(f, t, label) as (
+	select * from graph g
+	union all
+	select g.*
+	from graph g, search_graph sg
+	where g.f = sg.t
+) cycle f, t set is_cycle to 'Y' default 'N' using path
 select f, t, label from search_graph;
 
-select pg_get_viewdef('v_cycle');
+select pg_get_viewdef('v_cycle1');
+select pg_get_viewdef('v_cycle2');
 
-select * from v_cycle;
+select * from v_cycle1;
+select * from v_cycle2;
 
 --
 -- test multiple WITH queries