TopN變更相容性 - Realtime Compute for Apache Flink

本文為您介紹Top-N變更的可相容性和不可相容性詳情。

可相容的變更

修改partition key的順序，屬於完全相容變更。

--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順序，屬於完全相容變更。
select a, b, c from (
  select *,
   row_number() over (partition by b, a order by c) as rk
   from MyTable)
where rk < 3;

是否輸出rank number的值，不影響相容性，屬於完全相容。

-- 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;

-- 輸出rank number欄位：rk，屬於完全相容。
select a, b, c, rk from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

不相容的變更

如果rank是UpdateFastRank演算法，且上遊的Upsert Key發生了變化，屬於不相容變更。

新增、刪除、修改partition by key或者partition by key涉及欄位的計算邏輯發生變化，屬於不相容變更。

-- 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欄位：d，屬於不相容變更。
select a, b, c from (
  select *,
   row_number() over (partition by a, d order by c) as rk
   from MyTable)
where rk < 3;

-- 刪除partition by欄位：a，屬於不相容變更。
select a, b, c from (
  select *,
   row_number() over (order by c) as rk
   from MyTable)
where rk < 3;

-- 修改partition by欄位：a -> a + 1，屬於不相容變更。
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相關屬性（排序欄位和方向），屬於不相容變更。

-- 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，屬於不相容變更。
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)，屬於不相容變更。
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，屬於不相容變更。
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），屬於不相容變更。

-- 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，屬於不相容變更。
select a, b, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 5;

修改了輸入欄位，屬於不相容變更。

-- 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;

-- 新增輸入欄位d，屬於不相容變更。
select a, b, c, d from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

-- 刪除輸入欄位：b，屬於不相容變更。
select a, c from (
  select *,
   row_number() over (partition by a order by c) as rk
   from MyTable)
where rk < 3;

-- 修改輸入欄位：b -> b + 1，屬於不相容變更。
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;