Allow a foreign table CHECK constraint to be initially NOT VALID.

For a table, the constraint can be considered validated immediately,
because the table must be empty.  But for a foreign table this is
not necessarily the case.

Fixes a bug in commit f27a6b1.

Amit Langote, with some changes by me.

Discussion: http://postgr.es/m/d2b7419f-4a71-cf86-cc99-bfd0f359a1ea@lab.ntt.co.jp

Author: robertmhaas

src/backend/parser/parse_utilcmd.c

@@ -156,6 +156,7 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 	Oid			existing_relid;
 	ParseCallbackState pcbstate;
 	bool		like_found = false;
+	bool		is_foreign_table = IsA(stmt, CreateForeignTableStmt);
 
 	/*
 	 * We must not scribble on the passed-in CreateStmt, so copy it.  (This is
@@ -312,7 +313,7 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 	/*
 	 * Postprocess check constraints.
 	 */
-	transformCheckConstraints(&cxt, true);
+	transformCheckConstraints(&cxt, !is_foreign_table ? true : false);
 
 	/*
 	 * Output results.
@@ -1935,9 +1936,9 @@ transformCheckConstraints(CreateStmtContext *cxt, bool skipValidation)
 		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 creating a new table (but not a foreign 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)
 	{