sets default

Author: jennifersp

server/context.go

@@ -235,13 +235,13 @@ func (s *SessionManager) getOrCreateSession(ctx context.Context, conn *mysql.Con
 	return sess, nil
 }
 
-// InitSessionVariable sets a value to a parameter of a session at start.
-func (s *SessionManager) InitSessionVariable(ctx context.Context, conn *mysql.Conn, name, value string) error {
+// InitSessionDefaultVariable sets a default value to a parameter of a session at start.
+func (s *SessionManager) InitSessionDefaultVariable(ctx context.Context, conn *mysql.Conn, name, value string) error {
 	sess, err := s.getOrCreateSession(ctx, conn)
 	if err != nil {
 		return err
 	}
-	return sess.InitSessionVariable(s.ctxFactory(ctx, sql.WithSession(sess)), name, value)
+	return sess.InitSessionDefaultVariable(s.ctxFactory(ctx, sql.WithSession(sess)), name, value)
 }
 
 // NewContextWithQuery creates a new context for the session at the given conn.

sql/base_session.go

@@ -159,6 +159,30 @@ func (s *BaseSession) InitSessionVariable(ctx *Context, sysVarName string, value
 	return s.setSessVar(ctx, sysVar, value, true)
 }
 
+// InitSessionDefaultVariable implements the Session interface and is used to initialize variables (Including read-only variables)
+func (s *BaseSession) InitSessionDefaultVariable(ctx *Context, sysVarName string, value interface{}) error {
+	sysVar, _, ok := SystemVariables.GetGlobal(sysVarName)
+	if !ok {
+		return ErrUnknownSystemVariable.New(sysVarName)
+	}
+
+	sysVarName = strings.ToLower(sysVarName)
+	val, ok := s.systemVars[sysVarName]
+	if ok && val.Val != sysVar.GetDefault() {
+		return ErrSystemVariableReinitialized.New(sysVarName)
+	}
+	svv, err := sysVar.InitValue(ctx, "", value, false)
+	if err != nil {
+		return err
+	}
+	svv.Var.SetDefault(value)
+	s.systemVars[sysVarName] = svv
+	if sysVarName == characterSetResultsSysVarName {
+		s.charset = CharacterSet_Unspecified
+	}
+	return nil
+}
+
 func (s *BaseSession) setSessVar(ctx *Context, sysVar SystemVariable, newVal interface{}, init bool) error {
 	var svv SystemVarValue
 	var err error

sql/session.go

@@ -66,6 +66,8 @@ type Session interface {
 	Client() Client
 	// SetClient returns a new session with the given client.
 	SetClient(Client)
+	// InitSessionDefaultVariable sets the given value as the default value of given system variable for this session.
+	InitSessionDefaultVariable(ctx *Context, sysVarName string, value interface{}) error
 	// SetSessionVariable sets the given system variable to the value given for this session.
 	SetSessionVariable(ctx *Context, sysVarName string, value interface{}) error
 	// InitSessionVariable sets the given system variable to the value given for this session and will allow for