remove HasPreferStandbyTargetSessionAttr, rename error to indicate server is not standby

config.go

@@ -50,8 +50,6 @@ type Config struct {
 	// fallback config is tried. This allows implementing high availability behavior such as libpq does with target_session_attrs.
 	ValidateConnect ValidateConnectFunc
 
-	HasPreferStandbyTargetSessionAttr bool
-
 	// AfterConnect is called after ValidateConnect. It can be used to set up the connection (e.g. Set session variables
 	// or prepare statements). If this returns an error the connection attempt fails.
 	AfterConnect AfterConnectFunc
@@ -371,7 +369,6 @@ func ParseConfig(connString string) (*Config, error) {
 		config.ValidateConnect = ValidateConnectTargetSessionAttrsStandby
 	case "prefer-standby":
 		config.ValidateConnect = ValidateConnectTargetSessionAttrsPreferStandby
-		config.HasPreferStandbyTargetSessionAttr = true
 	case "any":
 		// do nothing
 	default:
@@ -825,7 +822,7 @@ func ValidateConnectTargetSessionAttrsPreferStandby(ctx context.Context, pgConn
 	}
 
 	if string(result.Rows[0][0]) != "t" {
-		return &preferStandbyNotFoundError{err: errors.New("server is not in hot standby mode")}
+		return &NotStandbyError{err: errors.New("server is not in hot standby mode")}
 	}
 
 	return nil

config_test.go

@@ -612,15 +612,14 @@ func TestParseConfig(t *testing.T) {
 			name:       "target_session_attrs prefer-standby",
 			connString: "postgres://jack:secret@localhost:5432/mydb?sslmode=disable&target_session_attrs=prefer-standby",
 			config: &pgconn.Config{
-				User:                              "jack",
-				Password:                          "secret",
-				Host:                              "localhost",
-				Port:                              5432,
-				Database:                          "mydb",
-				TLSConfig:                         nil,
-				RuntimeParams:                     map[string]string{},
-				ValidateConnect:                   pgconn.ValidateConnectTargetSessionAttrsPreferStandby,
-				HasPreferStandbyTargetSessionAttr: true,
+				User:            "jack",
+				Password:        "secret",
+				Host:            "localhost",
+				Port:            5432,
+				Database:        "mydb",
+				TLSConfig:       nil,
+				RuntimeParams:   map[string]string{},
+				ValidateConnect: pgconn.ValidateConnectTargetSessionAttrsPreferStandby,
 			},
 		},
 		{
@@ -785,7 +784,6 @@ func assertConfigsEqual(t *testing.T, expected, actual *pgconn.Config, testName
 	// Can't test function equality, so just test that they are set or not.
 	assert.Equalf(t, expected.ValidateConnect == nil, actual.ValidateConnect == nil, "%s - ValidateConnect", testName)
 	assert.Equalf(t, expected.AfterConnect == nil, actual.AfterConnect == nil, "%s - AfterConnect", testName)
-	assert.Equalf(t, expected.HasPreferStandbyTargetSessionAttr, actual.HasPreferStandbyTargetSessionAttr, "%s - HasPreferStandbyTargetSessionAttr", testName)
 
 	if assert.Equalf(t, expected.TLSConfig == nil, actual.TLSConfig == nil, "%s - TLSConfig", testName) {
 		if expected.TLSConfig != nil {

errors.go

@@ -220,19 +220,19 @@ func redactURL(u *url.URL) string {
 	return u.String()
 }
 
-type preferStandbyNotFoundError struct {
+type NotStandbyError struct {
 	err         error
 	safeToRetry bool
 }
 
-func (e *preferStandbyNotFoundError) Error() string {
+func (e *NotStandbyError) Error() string {
 	return fmt.Sprintf("standby server not found: %s", e.err.Error())
 }
 
-func (e *preferStandbyNotFoundError) SafeToRetry() bool {
+func (e *NotStandbyError) SafeToRetry() bool {
 	return e.safeToRetry
 }
 
-func (e *preferStandbyNotFoundError) Unwrap() error {
+func (e *NotStandbyError) Unwrap() error {
 	return e.err
 }

pgconn.go

@@ -167,8 +167,8 @@ func ConnectConfig(ctx context.Context, config *Config) (pgConn *PgConn, err err
 				pgerr.Code == ERRCODE_INSUFFICIENT_PRIVILEGE {
 				break
 			}
-		} else if cerr, ok := err.(*connectError); ok && config.HasPreferStandbyTargetSessionAttr {
-			if _, ok := cerr.err.(*preferStandbyNotFoundError); ok {
+		} else if cerr, ok := err.(*connectError); ok {
+			if _, ok := cerr.err.(*NotStandbyError); ok {
 				fallbackConfig = fc
 			}
 		}