feat: removing short cicuit in client use db (#1067)

* feat: adding force use db in client conn

* fix: just remove the short circuit all together

* add unit test

Signed-off-by: lance6716 <[email protected]>

---------

Signed-off-by: lance6716 <[email protected]>
Co-authored-by: lance6716 <[email protected]>

Author: vanhtuan0409

client/conn.go

@@ -268,10 +268,6 @@ func (c *Conn) SetTLSConfig(config *tls.Config) {
 }
 
 func (c *Conn) UseDB(dbName string) error {
-	if c.db == dbName {
-		return nil
-	}
-
 	if err := c.writeCommandStr(mysql.COM_INIT_DB, dbName); err != nil {
 		return errors.Trace(err)
 	}

client/conn_test.go

@@ -210,3 +210,30 @@ func (s *connTestSuite) TestSetQueryAttributes() {
 	}
 	require.Equal(s.T(), expected, s.c.queryAttributes)
 }
+
+func (s *connTestSuite) TestUseDB() {
+	_, err := s.c.Execute("create database if not exists proxier;")
+	require.NoError(s.T(), err)
+	err = s.c.UseDB("proxier")
+	require.NoError(s.T(), err)
+	result, err := s.c.Execute("select database();")
+	require.NoError(s.T(), err)
+	value, err := result.GetString(0, 0)
+	require.NoError(s.T(), err)
+	require.Equal(s.T(), "proxier", value)
+	_, err = s.c.Execute("drop database proxier;")
+	require.NoError(s.T(), err)
+	_, err = s.c.Execute("create database proxier;")
+	require.NoError(s.T(), err)
+	err = s.c.UseDB("proxier")
+	require.NoError(s.T(), err)
+	result, err = s.c.Execute("select database();")
+	require.NoError(s.T(), err)
+	value, err = result.GetString(0, 0)
+	require.NoError(s.T(), err)
+	require.Equal(s.T(), "proxier", value)
+	_, err = s.c.Execute("drop database proxier;")
+	require.NoError(s.T(), err)
+	err = s.c.UseDB("test")
+	require.NoError(s.T(), err)
+}