AWS Athena (Presto) 如何将地图转置为列 [英] AWS Athena (Presto) how to transpose map to columns

问题描述

AWS Athena 查询问题；

AWS Athena query question;

我的行中有一个嵌套映射，我想将其中的键转置为列.我可以像 items['label_a'] 一样明确地命名列，但在这种情况下，键实际上是动态的...

I have a nested map in my rows, of which I would like to transpose the keys to columns. I could name the columns explicitly like items['label_a'], but in this case the keys are actually dynamic...

从这些行:

{id=1, items={label_a=foo, label_b=foo}}
{id=2, items={label_a=bar, label_c=bar}}
{id=3, items={label_b=baz, label_c=baz}}

我想要一张这样的桌子:

I would like to get a table like so:

| id | label_a | label_b | label_c |
------------------------------------
| 1  |   foo   |   foo   |         |  
| 2  |   bar   |         |   bar   |  
| 3  |         |   baz   |   baz   |  

在 aws athena (presto version 0.172) 中是否可行以及如何做到这一点?

Is that possible and how to do this in aws athena (presto version 0.172)?

谢谢！

推荐答案

由于在查询执行开始之前需要规划器知道输出列这一事实，这无法以动态方式实现.

This is not possible in a dynamic manner due to the fact that output columns need to be know to the planner before the query execution starts.

在这里查看之前的讨论:https://github.com/prestosql/presto/issues/2448 和 https://github.com/prestosql/presto/issues/1206.

See the previous discussion here: https://github.com/prestosql/presto/issues/2448 and https://github.com/prestosql/presto/issues/1206.

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