我是新来的clickhouse，所以任何帮助都将不胜感激，我有一个表准时。从这里进口的
表的架构

CREATE TABLE default.ontime ( Year UInt17,  Quarter UInt8,  Month UInt8,  DayofMonth UInt8,  DayOfWeek UInt8,  FlightDate Date,  UniqueCarrier FixedString(7),  AirlineID Int32,  Carrier FixedString(2),
  TailNum String,  FlightNum String,  OriginAirportID Int32,  OriginAirportSeqID Int32,  OriginCityMarketID Int32,  Origin FixedString(5),  OriginCityName String,  OriginState FixedString(2),  OriginStateFips 
  String,  OriginStateName String,  OriginWac Int32,  DestAirportID Int32,  DestAirportSeqID Int32,  DestCityMarketID Int32,  Dest FixedString(5),  DestCityName String,  DestState FixedString(2),  
  DestStateFips String,  DestStateName String,  DestWac Int32,  CRSDepTime Int32,  DepTime Int32,  DepDelay Int32,  DepDelayMinutes Int32,  DepDel15 Int32,  DepartureDelayGroups String,  DepTimeBlk String,  TaxiOut 
  Int32,  WheelsOff Int32,  WheelsOn Int32,  TaxiIn Int32,  CRSArrTime Int32,  ArrTime Int32,  ArrDelay Int32,  ArrDelayMinutes Int32,  ArrDel15 Int32,  ArrivalDelayGroups Int32,  ArrTimeBlk String,  Cancelled 
  UInt8,  CancellationCode FixedString(1),  Diverted UInt8,  CRSElapsedTime Int32,  ActualElapsedTime Int32,  AirTime Int32,  Flights Int32,  Distance Int32,  DistanceGroup UInt8,  CarrierDelay Int32,  WeatherDelay 
  Int32,  NASDelay Int32,  SecurityDelay Int32,  LateAircraftDelay Int32,  FirstDepTime String,  TotalAddGTime String,  LongestAddGTime String,  DivAirportLandings String,  DivReachedDest String,  
  DivActualElapsedTime String,  DivArrDelay String,  DivDistance String,  Div1Airport String,  Div1AirportID Int32,  Div1AirportSeqID Int32,  Div1WheelsOn String,  Div1TotalGTime String,  Div1LongestGTime String,  
  Div1WheelsOff String,  Div1TailNum String,  Div2Airport String,  Div2AirportID Int32,  Div2AirportSeqID Int32,  Div2WheelsOn String,  Div2TotalGTime String,  Div2LongestGTime String,  Div2WheelsOff String,  
  Div2TailNum String,  Div3Airport String,  Div3AirportID Int32,  Div3AirportSeqID Int32,  Div3WheelsOn String,  Div3TotalGTime String,  Div3LongestGTime String,  Div3WheelsOff String,  Div3TailNum String,  
  Div4Airport String,  Div4AirportID Int32,  Div4AirportSeqID Int32,  Div4WheelsOn String,  Div4TotalGTime 
  String,  Div4LongestGTime String,  Div4WheelsOff String,  Div4TailNum String,  Div5Airport String,  
  Div5AirportID Int32,  Div5AirportSeqID Int32,  Div5WheelsOn String,  Div5TotalGTime String,  
  Div5LongestGTime String,  Div5WheelsOff String,  Div5TailNum String)
   ENGINE = MergeTree(FlightDate, (Year, FlightDate), 8192)

有数百万的记录。我要做的是对表进行快照，在取消附加表之后，我要从快照中恢复
创建快照

clickhouse-client --query="SELECT * FROM ontime FORMAT csv" > ontime.csv

以csv格式备份13272488条记录==>所用时间1分钟12秒备份大小5 gb

// Saving the meta data 
clickhouse-client --query="SHOW CREATE TABLE ontime" --format=TabSeparatedRaw > ontime_meta.sql

现在删除这个表，因为我提到了官方文件
命令是 ALTER TABLE table_name DROP PARTITION partition_expr 我试过这些变种，但都没用。

ALTER TABLE ontime  DETACH PARTITION (Year, FlightDate);
    ALTER TABLE ontime  DETACH PARTITION FlightDate;
    ALTER TABLE ontime  DETACH PARTITION 8192;
    ALTER TABLE ontime DETACH PARTITION (FlightDate, (Year, FlightDate), 8192)

所以我的问题是如何指定分区表达式？