Question

我正在运行下面的查询，大约200万个蜂巢。有没有办法改善性能？源配置单元表是created_date

的分区列

 select t.id,
    case when t.amt_1_rank < 0.3*f.amt_1_count then t.amt_1 else null end as amt_1,
    case when t.amt_2_rank < 0.3*f.amt_2_count then t.amt_2 else null end as amt_2,
..
..
..  -- Like wise 30 columns e.g. amt_3,amt_3...
     from (
    select a.id,
    a.amt_1,
    row_number() over (ORDER BY cast(a.amt_1 AS DECIMAL(8,7)) DESC) AS amt_1_rank,
    a.amt_2,
    row_number() over (ORDER BY cast(a.amt_2 AS DECIMAL(8,7)) DESC) AS amt_2_rank
    from source_table a WHERE created_date='2017-10-15' )t
    join 
    ( 
    SELECT count(case when amt_1='.' then null else 1 end) AS amt_1_count,
    count(case when amt_2='.' then null else 1 end) AS amt_2_count,
..
..

    FROM   source_table
    WHERE  created_date='2017-10-15' 
    ) f

Answer 1

你可以不加入来做到这一点：

select t.id,
    case when t.amt_1_rank < 0.3*t.amt_1_count then t.amt_1 else null end as amt_1,
    case when t.amt_2_rank < 0.3*t.amt_2_count then t.amt_2 else null end as amt_2,
..
..
..  -- Like wise 30 columns e.g. amt_3,amt_3...
     from (
    select a.id,
           a.amt_1,
           row_number() over (ORDER BY cast(a.amt_1 AS DECIMAL(8,7)) DESC) AS amt_1_rank,
           a.amt_2,
           row_number() over (ORDER BY cast(a.amt_2 AS DECIMAL(8,7)) DESC) AS amt_2_rank,
           count(amt_1_flag) over()                                        AS amt_1_count,
           count(amt_2_flag) over()                                        AS amt_2_count
      from 
           (select a.*,
                   case when amt_1='.' then null else 1 end as amt_1_flag,
                   case when amt_2='.' then null else 1 end as amt_2_flag
              from source_table a WHERE created_date='2017-10-15' 
            )a  

           )t

如何提高蜂巢的性能

1 个答案: