Mark CHECK constraints declared NOT VALID valid if created with table.

FOREIGN KEY constraints have behaved this way for a long time, but for
some reason the behavior of CHECK constraints has been inconsistent up
until now.

Amit Langote and Amul Sul, with assorted tweaks by me.

Author: robertmhaas

src/backend/catalog/heap.c

@@ -2349,7 +2349,7 @@ AddRelationNewConstraints(Relation rel,
 		 * OK, store it.
 		 */
 		constrOid =
-			StoreRelCheck(rel, ccname, expr, !cdef->skip_validation, is_local,
+			StoreRelCheck(rel, ccname, expr, cdef->initially_valid, is_local,
 						  is_local ? 0 : 1, cdef->is_no_inherit, is_internal);
 
 		numchecks++;

src/backend/parser/gram.y

@@ -3080,6 +3080,8 @@ ColConstraintElem:
 					n->is_no_inherit = $5;
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
+					n->skip_validation = false;
+					n->initially_valid = true;
 					$$ = (Node *)n;
 				}
 			| DEFAULT b_expr

src/backend/parser/parse_utilcmd.c

@@ -120,6 +120,8 @@ static IndexStmt *transformIndexConstraint(Constraint *constraint,
 static void transformFKConstraints(CreateStmtContext *cxt,
 					   bool skipValidation,
 					   bool isAddConstraint);
+static void transformCheckConstraints(CreateStmtContext *cxt,
+						bool skipValidation);
 static void transformConstraintAttrs(CreateStmtContext *cxt,
 						 List *constraintList);
 static void transformColumnType(CreateStmtContext *cxt, ColumnDef *column);
@@ -319,6 +321,11 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 	 */
 	transformFKConstraints(&cxt, true, false);
 
+	/*
+	 * Postprocess check constraints.
+	 */
+	transformCheckConstraints(&cxt, true);
+
 	/*
 	 * Output results.
 	 */
@@ -1914,6 +1921,40 @@ transformIndexConstraint(Constraint *constraint, CreateStmtContext *cxt)
 	return index;
 }
 
+/*
+ * transformCheckConstraints
+ *		handle CHECK constraints
+ *
+ * Right now, there's nothing to do here when called from ALTER TABLE,
+ * but the other constraint-transformation functions are called in both
+ * the CREATE TABLE and ALTER TABLE paths, so do the same here, and just
+ * don't do anything if we're not authorized to skip validation.
+ */
+static void
+transformCheckConstraints(CreateStmtContext *cxt, bool skipValidation)
+{
+	ListCell   *ckclist;
+
+	if (cxt->ckconstraints == NIL)
+		return;
+
+	/*
+	 * If creating a new table, we can safely skip validation of check
+	 * constraints, and nonetheless mark them valid.  (This will override
+	 * any user-supplied NOT VALID flag.)
+	 */
+	if (skipValidation)
+	{
+		foreach(ckclist, cxt->ckconstraints)
+		{
+			Constraint *constraint = (Constraint *) lfirst(ckclist);
+
+			constraint->skip_validation = true;
+			constraint->initially_valid = true;
+		}
+	}
+}
+
 /*
  * transformFKConstraints
  *		handle FOREIGN KEY constraints
@@ -2567,10 +2608,10 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
 	save_alist = cxt.alist;
 	cxt.alist = NIL;
 
-	/* Postprocess index and FK constraints */
+	/* Postprocess constraints */
 	transformIndexConstraints(&cxt);
-
 	transformFKConstraints(&cxt, skipValidation, true);
+	transformCheckConstraints(&cxt, false);
 
 	/*
 	 * Push any index-creation commands into the ALTER, so that they can be

src/test/regress/expected/alter_table.out

@@ -380,7 +380,16 @@ DROP TABLE tmp2;
 -- NOT VALID with plan invalidation -- ensure we don't use a constraint for
 -- exclusion until validated
 set constraint_exclusion TO 'partition';
-create table nv_parent (d date);
+create table nv_parent (d date, check (false) no inherit not valid);
+-- not valid constraint added at creation time should automatically become valid
+\d nv_parent
+ Table "public.nv_parent"
+ Column | Type | Modifiers 
+--------+------+-----------
+ d      | date | 
+Check constraints:
+    "nv_parent_check" CHECK (false) NO INHERIT
+
 create table nv_child_2010 () inherits (nv_parent);
 create table nv_child_2011 () inherits (nv_parent);
 alter table nv_child_2010 add check (d between '2010-01-01'::date and '2010-12-31'::date) not valid;

src/test/regress/sql/alter_table.sql

@@ -327,7 +327,10 @@ DROP TABLE tmp2;
 -- NOT VALID with plan invalidation -- ensure we don't use a constraint for
 -- exclusion until validated
 set constraint_exclusion TO 'partition';
-create table nv_parent (d date);
+create table nv_parent (d date, check (false) no inherit not valid);
+-- not valid constraint added at creation time should automatically become valid
+\d nv_parent
+
 create table nv_child_2010 () inherits (nv_parent);
 create table nv_child_2011 () inherits (nv_parent);
 alter table nv_child_2010 add check (d between '2010-01-01'::date and '2010-12-31'::date) not valid;