Fix VALIDATE CONSTRAINT to consider NO INHERIT attribute.

Currently, trying to validate a NO INHERIT constraint on the parent will
search for the constraint in child tables (where it is not supposed to
exist), wrongly causing a "constraint does not exist" error.

Amit Langote, per a report from Hans Buschmann.

Discussion: http://postgr.es/m/20170421184012.24362.19@wrigleys.postgresql.org

Author: robertmhaas

src/backend/commands/tablecmds.c

@@ -6903,9 +6903,10 @@ ATExecValidateConstraint(Relation rel, char *constrName, bool recurse,
 
 			/*
 			 * If we're recursing, the parent has already done this, so skip
-			 * it.
+			 * it.  Also, if the constraint is a NO INHERIT constraint, we
+			 * shouldn't try to look for it in the children.
 			 */
-			if (!recursing)
+			if (!recursing && !con->connoinherit)
 				children = find_all_inheritors(RelationGetRelid(rel),
 											   lockmode, NULL);
 

src/test/regress/expected/alter_table.out

@@ -367,6 +367,26 @@ NOTICE:  merging constraint "identity" with inherited definition
 ALTER TABLE tmp3 VALIDATE CONSTRAINT identity;
 NOTICE:  boo: 16
 NOTICE:  boo: 20
+-- A NO INHERIT constraint should not be looked for in children during VALIDATE CONSTRAINT
+create table parent_noinh_convalid (a int);
+create table child_noinh_convalid () inherits (parent_noinh_convalid);
+insert into parent_noinh_convalid values (1);
+insert into child_noinh_convalid values (1);
+alter table parent_noinh_convalid add constraint check_a_is_2 check (a = 2) no inherit not valid;
+-- fail, because of the row in parent
+alter table parent_noinh_convalid validate constraint check_a_is_2;
+ERROR:  check constraint "check_a_is_2" is violated by some row
+delete from only parent_noinh_convalid;
+-- ok (parent itself contains no violating rows)
+alter table parent_noinh_convalid validate constraint check_a_is_2;
+select convalidated from pg_constraint where conrelid = 'parent_noinh_convalid'::regclass and conname = 'check_a_is_2';
+ convalidated 
+--------------
+ t
+(1 row)
+
+-- cleanup
+drop table parent_noinh_convalid, child_noinh_convalid;
 -- Try (and fail) to create constraint from tmp5(a) to tmp4(a) - unique constraint on
 -- tmp4 is a,b
 ALTER TABLE tmp5 add constraint tmpconstr foreign key(a) references tmp4(a) match full;

src/test/regress/sql/alter_table.sql

@@ -307,6 +307,21 @@ ALTER TABLE tmp7 ADD CONSTRAINT identity CHECK (b = boo(b));
 ALTER TABLE tmp3 ADD CONSTRAINT IDENTITY check (b = boo(b)) NOT VALID;
 ALTER TABLE tmp3 VALIDATE CONSTRAINT identity;
 
+-- A NO INHERIT constraint should not be looked for in children during VALIDATE CONSTRAINT
+create table parent_noinh_convalid (a int);
+create table child_noinh_convalid () inherits (parent_noinh_convalid);
+insert into parent_noinh_convalid values (1);
+insert into child_noinh_convalid values (1);
+alter table parent_noinh_convalid add constraint check_a_is_2 check (a = 2) no inherit not valid;
+-- fail, because of the row in parent
+alter table parent_noinh_convalid validate constraint check_a_is_2;
+delete from only parent_noinh_convalid;
+-- ok (parent itself contains no violating rows)
+alter table parent_noinh_convalid validate constraint check_a_is_2;
+select convalidated from pg_constraint where conrelid = 'parent_noinh_convalid'::regclass and conname = 'check_a_is_2';
+-- cleanup
+drop table parent_noinh_convalid, child_noinh_convalid;
+
 -- Try (and fail) to create constraint from tmp5(a) to tmp4(a) - unique constraint on
 -- tmp4 is a,b