SELECT MASTER_POS_WAIT('source_log_file', source_log_pos [, timeout][, channel])

This is actually a function, not a statement. 这实际上是一个函数，而不是一个语句。It is used to ensure that the replica has read and executed events up to a given position in the source's binary log. 它用于确保复制副本在源二进制日志中的给定位置读取和执行事件。See Section 12.24, “Miscellaneous Functions”, for a full description.有关完整说明，请参阅第12.24节，“杂项函数”。