Make FKs valid at creation when added as column constraints.

Bug report from Alvaro Herrera

src/backend/commands/tablecmds.c

@@ -5595,7 +5595,7 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 									  CONSTRAINT_FOREIGN,
 									  fkconstraint->deferrable,
 									  fkconstraint->initdeferred,
-									  !fkconstraint->skip_validation,
+									  fkconstraint->initially_valid,
 									  RelationGetRelid(rel),
 									  fkattnum,
 									  numfks,

src/backend/nodes/copyfuncs.c

@@ -2341,6 +2341,7 @@ _copyConstraint(Constraint *from)
 	COPY_SCALAR_FIELD(fk_upd_action);
 	COPY_SCALAR_FIELD(fk_del_action);
 	COPY_SCALAR_FIELD(skip_validation);
+	COPY_SCALAR_FIELD(initially_valid);
 
 	return newnode;
 }

src/backend/nodes/equalfuncs.c

@@ -2270,6 +2270,7 @@ _equalConstraint(Constraint *a, Constraint *b)
 	COMPARE_SCALAR_FIELD(fk_upd_action);
 	COMPARE_SCALAR_FIELD(fk_del_action);
 	COMPARE_SCALAR_FIELD(skip_validation);
+	COMPARE_SCALAR_FIELD(initially_valid);
 
 	return true;
 }

src/backend/nodes/outfuncs.c

@@ -2625,6 +2625,7 @@ _outConstraint(StringInfo str, Constraint *node)
 			WRITE_CHAR_FIELD(fk_upd_action);
 			WRITE_CHAR_FIELD(fk_del_action);
 			WRITE_BOOL_FIELD(skip_validation);
+			WRITE_BOOL_FIELD(initially_valid);
 			break;
 
 		case CONSTR_ATTR_DEFERRABLE:

src/backend/parser/gram.y

@@ -2621,6 +2621,7 @@ ColConstraintElem:
 					n->fk_upd_action	= (char) ($5 >> 8);
 					n->fk_del_action	= (char) ($5 & 0xFF);
 					n->skip_validation  = FALSE;
+					n->initially_valid  = true;
 					$$ = (Node *)n;
 				}
 		;
@@ -2820,6 +2821,7 @@ ConstraintElem:
 					n->deferrable		= ($11 & 1) != 0;
 					n->initdeferred		= ($11 & 2) != 0;
 					n->skip_validation  = false;
+					n->initially_valid  = true;
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -2836,6 +2838,7 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					n->skip_validation  = true;
+					n->initially_valid  = false;
 					$$ = (Node *)n;
 				}
 		;

src/backend/parser/parse_utilcmd.c

@@ -1696,6 +1696,7 @@ transformFKConstraints(CreateStmtContext *cxt,
 			Constraint *constraint = (Constraint *) lfirst(fkclist);
 
 			constraint->skip_validation = true;
+			constraint->initially_valid  = true;
 		}
 	}
 

src/include/nodes/parsenodes.h

@@ -1536,6 +1536,7 @@ typedef struct Constraint
 	char		fk_upd_action;	/* ON UPDATE action */
 	char		fk_del_action;	/* ON DELETE action */
 	bool		skip_validation;	/* skip validation of existing rows? */
+	bool		initially_valid;	/* start the new constraint as valid */
 } Constraint;
 
 /* ----------------------