Restrict state connection search path (#342)

Restrict the search path of the connection used by the state package to
only the state schema (the schema that contains the `migrations` table).

This ensures that any column types that might reside in other schema are
always qualified with the schema name in the internal schema
representation. Without the restriction of the search path, these type
names would be unqualified if they lived in a schema that was on the
search path used by the state connection.

The representation (qualified/unqualified) of type names in the internal
schema is ultimately due to how the
[format-type](https://www.postgresql.org/docs/9.5/functions-info.html)
function behaves; types in the `search_path` of the caller are
unqualified, otherwise they are qualified.

pkg/state/state.go

@@ -340,7 +340,14 @@ type State struct {
 }
 
 func New(ctx context.Context, pgURL, stateSchema string) (*State, error) {
-	conn, err := sql.Open("postgres", pgURL)
+	dsn, err := pq.ParseURL(pgURL)
+	if err != nil {
+		dsn = pgURL
+	}
+
+	dsn += " search_path=" + stateSchema
+
+	conn, err := sql.Open("postgres", dsn)
 	if err != nil {
 		return nil, err
 	}

pkg/state/state_test.go

@@ -705,6 +705,30 @@ func TestReadSchema(t *testing.T) {
 					},
 				},
 			},
+			{
+				name:       "column whose type is a UDT in another schema should have the type prefixed with the schema",
+				createStmt: "CREATE DOMAIN email_type AS varchar(255); CREATE TABLE public.table1 (a email_type);",
+				wantSchema: &schema.Schema{
+					Name: "public",
+					Tables: map[string]schema.Table{
+						"table1": {
+							Name: "table1",
+							Columns: map[string]schema.Column{
+								"a": {
+									Name:     "a",
+									Type:     "public.email_type",
+									Nullable: true,
+								},
+							},
+							PrimaryKey:        []string{},
+							Indexes:           map[string]schema.Index{},
+							ForeignKeys:       map[string]schema.ForeignKey{},
+							CheckConstraints:  map[string]schema.CheckConstraint{},
+							UniqueConstraints: map[string]schema.UniqueConstraint{},
+						},
+					},
+				},
+			},
 		}
 
 		for _, tt := range tests {