SparkSql拼接SQL优化

减少对象的创建

  val dfHive: DataFrame = spark.sql("select "+str+ " from t_emp "+joinName+" t_dept on "+joinCondition)
//优化后
    val builder = new StringBuilder("select ")
    val sql = builder.append(str).append(" from t_emp ").append(joinName).append(" t_dept on ").append(joinCondition).toString()
    val dfHive: DataFrame = spark.sql(sql)