Hive內置row_number

hive rownumber內置函數使用例子

• Hive-0.11.0中內置row_number函數

  org.apache.hadoop.hive.ql.exe.FunctionRegistry 
  
  
  registerHiveUDAFsAsWindowFunctions();
  registerWindowFunction("row_number", new GenericUDAFRowNumber());  --row_number實現類
  registerWindowFunction("rank", new GenericUDAFRank());
  registerWindowFunction("dense_rank", new GenericUDAFDenseRank());
  registerWindowFunction("percent_rank", new GenericUDAFPercentRank());
  registerWindowFunction("cume_dist", new GenericUDAFCumeDist());
  registerWindowFunction("ntile", new GenericUDAFNTile());
  registerWindowFunction("first_value", new GenericUDAFFirstValue());
  registerWindowFunction("last_value", new GenericUDAFLastValue());
  registerWindowFunction(LEAD_FUNC_NAME, new GenericUDAFLead(), false);
  registerWindowFunction(LAG_FUNC_NAME, new GenericUDAFLag(), false);
  

• 使用的DEMO

  • 從test_s表中根據c1字段除重，選取c2最大的值，導入test_c表.

• DEMO

    hive> 
    desc test_s;
    OK
    col_name data_type      comment
    c1                      int                     None                
    c2                      string                  None                
    Time taken: 1.87 seconds, Fetched: 2 row(s)

    hive> 
        > select * from test_s;
    OK
    c1      c2
    1       str1
    2       str2
    3       str3
    3       str31
    3       str33
    4       str41
    4       str42
    Time taken: 0.671 seconds, Fetched: 7 row(s)

    hive> select c1,c2,row_number() over (distribute by c1
        > sort by c2 desc) rownum
        >   from test_s ;

    OK
    c1      c2      rownum
    1       str1    1
    2       str2    1
    3       str33   1
    3       str31   2
    3       str3    3
    4       str42   1
    4       str41   2
    Time taken: 17.23 seconds, Fetched: 7 row(s)

    hive> 
        > 
        > desc test_c;
    OK
    col_name data_type      comment
    c1                      int                     None                
    c2                      string                  None                
    Time taken: 0.118 seconds, Fetched: 2 row(s)


    hive> 
        > insert into table test_c
        > select c1,c2
        > from (
        > select c1,c2,row_number() over (distribute by c1
        > sort by c2 desc) rownum
        >   from test_s 
        > ) aa
        > where aa.rownum = 1;
        OK
        Time taken: 19.609 seconds

    hive> 
        > 
        > 
        > 
        > select * from test_c;
        OK
        c1      c2
        1       str1
        2       str2
        3       str33
        4       str42
        Time taken: 0.144 seconds, Fetched: 4 row(s)