TopN变更兼容性_实时计算 Flink版(Flink)-阿里云帮助中心

本文为您介绍Top-N变更的可兼容性和不可兼容性详情。

可兼容的变更

修改partition key的顺序，属于完全兼容变更。

--原始
select a, b, c from (
  select *,
   row_number() over (partition by a, b order by c) as rk
   from MyTable)
where rk < 3;

-- 修改partition key顺序，属于完全兼容变更。
select a, b, c from (
  select *,
   row_number() over (partition by b, a order by c) as rk
   from MyTable)
where rk < 3;

是否输出rank number的值，不影响兼容性，属于完全兼容。

-- 原始SQL。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

-- 输出rank number字段：rk，属于完全兼容。
select a, b, c, rk from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

不兼容的变更

如果rank是UpdateFastRank算法，且上游的Upsert Key发生了变化，属于不兼容变更。

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，属于不兼容变更。

-- 原始SQL。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

-- 新增partition by字段：d，属于不兼容变更。
select a, b, c from (
  select *,
   row_number() over (partition by a, d order by c) as rk
   from MyTable)
where rk < 3;

-- 删除partition by字段：a，属于不兼容变更。
select a, b, c from (
  select *,
   row_number() over (order by c) as rk
   from MyTable)
where rk < 3;

-- 修改partition by字段：a -> a + 1，属于不兼容变更。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from (select a + 1 as a, b, c from MyTable))
where rk < 3;

修改order by相关属性（排序字段和方向），属于不兼容变更。

-- 原始SQL。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

-- 修改order key：c -> b，属于不兼容变更。
select a, b, c from (
  select *,
   row_number() over (partition by a order by b) as rk
   from MyTable)
where rk < 3;

-- 修改order key：c -> substring(c, 1, 5)，属于不兼容变更。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from (select a, b, substring(c, 1, 5) as c from MyTable))
where rk < 3;

-- 修改order：asc -> desc，属于不兼容变更。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c desc) as rk
   from MyTable)
where rk < 3;

修改rank range的值（Top-N中N的值），属于不兼容变更。

-- 原始SQL。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

-- 修改rank range：3 -> 5，属于不兼容变更。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 5;

修改了输入字段，属于不兼容变更。

-- 原始SQL。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

-- 新增输入字段d，属于不兼容变更。
select a, b, c, d from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

-- 删除输入字段：b，属于不兼容变更。
select a, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

-- 修改输入字段：b -> b + 1，属于不兼容变更。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from (select a, b + 1 as b, c from MyTable))
where rk < 3;