Window Top-N修改的兼容性_实时计算 Flink版(Flink)-阿里云帮助中心

Window TOP-N需要同时遵循Window TVF和Top-N两者的修改要求，支持的兼容性修改较少。本文为您介绍Window Top-N修改的可兼容性和不可兼容性详情。

可兼容的修改

新增、删除window属性字段，该修改属于完全兼容修改。

-- 原始SQL。
select a, b, c, window_start from (
  select *,
      row_number() over (partition by b, window_start, window_end order by c) as rk
  from (
    select a,
      sum(b) as b,
      max(c) as c,
        window_start,
        window_end
    from table (tumble(table MyTable, descriptor(ts), interval '1' minute))
      group by a, window_start, window_end)
  ) where rk < 3;


-- 新增window end，该修改属于完全兼容修改。
select a, b, c, window_start, window_end from (
  select *,
      row_number() over (partition by b, window_start, window_end order by c) as rk
  from (
    select a,
      sum(b) as b,
      max(c) as c,
        window_start,
        window_end
    from table (tumble(table MyTable, descriptor(ts), interval '1' minute))
      group by a, window_start, window_end)
  ) where rk < 3;

是否输出rank number的值，不影响兼容性，该修改属于完全兼容修改。

-- 原始SQL。
select a, b, c, window_start from (
  select *,
      row_number() over (partition by b, window_start, window_end order by c) as rk
  from (
    select a,
      sum(b) as b,
      max(c) as c,
        window_start,
        window_end
    from table (tumble(table MyTable, descriptor(ts), interval '1' minute))
      group by a, window_start, window_end)
  ) where rk < 3;


-- 输入rank number值：rk，该修改属于完全兼容修改。
select a, b, c, window_start, rk from (
  select *,
      row_number() over (partition by b, window_start, window_end order by c) as rk
  from (
    select a,
      sum(b) as b,
      max(c) as c,
        window_start,
        window_end
    from table (tumble(table MyTable, descriptor(ts), interval '1' minute))
      group by a, window_start, window_end)
  ) where rk < 3;

不兼容的修改

修改window相关属性（window 的类型，window 的大小，时间相关属性），该修改属于不兼容修改。
示例可参见Window TVF修改window相关属性示例，详情请参见不兼容的修改。
新增、删除、修改统计维度（group key）或者统计维度涉及字段的计算逻辑发生变化，该修改属于不兼容修改。
示例可参见Window TVF修改group key示例，详情请参见不兼容的修改。

新增、删除、修改统计指标，该修改属于不兼容修改。TOP-N的输入发生变化，该修改属于不兼容修改。

-- 原始SQL。
select a, b, c, window_start from (
  select *,
      row_number() over (partition by b, window_start, window_end order by c) as rk
  from (
    select a,
      sum(b) as b,
      max(c) as c,
        window_start,
        window_end
    from table (tumble(table MyTable, descriptor(ts), interval '1' minute))
      group by a, window_start, window_end)
  ) where rk < 3;

-- 新增统计指标：min(d) as d，属于不兼容修改。
-- 该修改会导致TOP-N的输入发生变化。
select a, b, c, d, window_start from (
  select *,
      row_number() over (partition by b, window_start, window_end order by c) as rk
  from (
    select a,
      sum(b) as b,
      max(c) as c,
      min(d) as d,
        window_start,
        window_end
    from table (tumble(table MyTable, descriptor(ts), interval '1' minute))
      group by a, window_start, window_end)
  ) where rk < 3;

新增、删除、修改partition by key或者partition by key涉及字段的计算逻辑发生变化，该修改属于不兼容修改。
示例可参见Top N修改partition by key示例，详情请参见不兼容的修改。
修改order by相关属性（排序字段和方向），该修改属于不兼容修改。
示例可参见Top N修改ordery by key示例，详情请参见不兼容的修改。
修改rank range的值（Top N中N 的值），则该修改属于不兼容修改。
示例可参见Top N修改rank range示例，详情请参见不兼容的修改。