[GitHub] [arrow-datafusion] ovr opened a new issue, #2442: ArrayIndex support with expression as key

[GitBox <gi...@apache.org>]

ovr opened a new issue, #2442:
URL: https://github.com/apache/arrow-datafusion/issues/2442

   Hello!
   
   ```sql
   SELECT r.value[1 + 1] FROM (SELECT array[1,2,3] as value, 1 as key UNION ALL SELECT array[1,2,3] as value, 1 as key) as r;
   +------------------------------+
   | r.value[Int64(1) + Int64(1)] |
   +------------------------------+
   | 3                            |
   | 3                            |
   +------------------------------+
   ```
   
   
   ```sql
   SELECT r.key, r.value[r.key] FROM (SELECT array[1,2,3] as value, 1 as key UNION ALL SELECT array[1,2,3] as value, 1 as key) as r;
   +-----+----------------+
   | key | r.value[r.key] |
   +-----+----------------+
   | 1   | 2              |
   | 1   | 2              |
   +-----+----------------+
   ```
   
   ```sql
   SELECT (ARRAY[1,2,3])[1 + 1];
   ```
   
   **Describe the solution you'd like**
   
   I would like to split `GetIndexedExpr` into `MapAccessExpr` (will continue to accept `key` as `ScalarValue)` & `ArrayIndexExpr` (will use `PhysicalExpr` for key)
   
   **Describe alternatives you've considered**
   
   Making key as `PhysicalExpr`for `GetIndexedExpr` but it makes a problem with type detection for a field of a `Struct` type. Probably, it's why PostgreSQL doesn't allow expression in MapAccess.
   
   **Additional context**
   
   I have drafted already a branch that supports it.
   
   <img width="1478" alt="image" src="https://user-images.githubusercontent.com/572096/166719763-04922c76-1241-47f7-95f3-e2434789a0c3.png">
   
   


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