[function] array_flatten

[wangsimo0]

need a function to flatten one layer of nested arrays.

description

Flattens an array(array(T)) to an array(T) by concatenating the contained arrays.

syntax

array_flatten(expr)

in which, expr is an nested array.

examples

SELECT array_flatten([[1, 2], [1, 4]]);
 [1,2,1,4]

select array_flatten([[[1],[2]],[[3],[4]]]);
 [[1], [2], [3], [4]] 

[chenlong1993]

I want try it

[wangxiaobaidu11]

I want to take it

[kateshaowanjou]

I want try it

Sorry I missed your message.😂 Can you take another one maybe? We appreciate your willingness to contribute to the community! ❤️

[DionysusG]

@kateshaowanjou Can you assign this task to me? Also, can @wangsimo0 provide more design guides on the functions?
I am concerned with the following issues:

1. What is the scenario in which we shall use the function? Wheteher we can make a recursive function?
2. What do you mean by array? STL array? Or do you have your array implementation?
3. How shall we decide the size of the flattened array? Decide in advance? Use a dynamic array to flatten the array in the first place?

[wangsimo0]

Hi @DionysusG , thanks a lot!
I just modified the function's design. I think flatten one layer is more reasonable like snowflake and trino. and this will help us in trino's compatibility too. so it won't be a recursive function and I think it will make more sense and easier to implement. what do you think?

reference:
https://trino.io/docs/current/functions/array.html?highlight=flatten#flatten
https://docs.snowflake.com/en/sql-reference/functions/array_flatten

[sergeyshaykhullin]

Any workaround to flatten arrays in 3.1.x?

[sfwang218]

@kateshaowanjou Excuse me, Has this issue been resolved? If not, can you assign it to me?

Sure, already did! If you have any questions, you are welcome to discuss with us. If you prefer to use wechat, here's the link:https://853921.ma3you.cn/articles/b12e90J/