func (c *ClientConn) handleUseDB(dbName string) error {
var co *backend.BackendConn
var err error
if len(dbName) == 0 {
return fmt.Errorf("must have database, the length of dbName is zero")
}
if c.schema == nil {
return mysql.NewDefaultError(mysql.ER_NO_DB_ERROR)
}
nodeName := c.schema.rule.DefaultRule.Nodes[0]
n := c.proxy.GetNode(nodeName)
//get the connection from slave preferentially
co, err = n.GetSlaveConn()
if err != nil {
co, err = n.GetMasterConn()
}
defer c.closeConn(co, false)
if err != nil {
return err
}
if err = co.UseDB(dbName); err != nil {
return err
}
c.db = dbName
return c.writeOK(nil)
}
