### POSEXPLODE 

#### Description

The `posexplode` function is used to expand an input array or map type expression `expr` into multiple rows of data, adding a position column to each row to indicate the relative position of the element in the original array or map. This function can be used directly or in conjunction with `LATERAL VIEW` to achieve data expansion in more complex queries.

#### Functionality

1. For array type input, `posexplode` expands each element in the array into a row, adding columns named `pos` and `col` to represent the position and value of the element, respectively.
2. For map type input, `posexplode` expands each key-value pair in the map into a row, adding columns named `pos`, `key`, and `value` to represent the position, key, and value of the element, respectively.

#### Parameters

* `expr`: Input array `array<T>` or map `map<K, V>` type.

#### Return Results

* For array type input, the return type is `int, T`.
* For map type input, the return type is `int, K, V`.

#### Usage Example

1. Expand array type input:
   ```sql
   SELECT posexplode(array(1, 2, 3));
   +-----+-----+
   | pos | col |
   +-----+-----+
   | 0   | 1   |
   | 1   | 2   |
   | 2   | 3   |
   +-----+-----+
   ```
2. Expand the input of the mapping type:
   ```sql
   SELECT posexplode(map("a", 1, "b", 2, "c", 3));
   +-----+-----+-------+
   | pos | key | value |
   +-----+-----+-------+
   | 0   | a   | 1     |
   | 1   | b   | 2     |
   | 2   | c   | 3     |
   +-----+-----+-------+
   ```
3. Using in combination with `LATERAL VIEW`:
   ```sql
   SELECT word, pos, ex
   FROM VALUES ('hello') AS vt(word)
   LATERAL VIEW posexplode(array(5, 6)) lv AS pos, ex;
   +-------+-----+----+
   | word  | pos | ex |
   +-------+-----+----+
   | hello | 0   | 5  |
   | hello | 1   | 6  |
   +-------+-----+----+
   ```
4. Expand the array and filter specific elements:
   ```SQL
   SELECT pos, col
   FROM  posexplode(array(1, 2, 3, 4)) AS t(pos, col) 
   WHERE col % 2 = 0;
   +-----+-----+
   | pos | col |
   +-----+-----+
   | 1   | 2   |
   | 3   | 4   |
   +-----+-----+
   ```
5. Expand the mapping and calculate the sum of values:
   ```SQL
   SELECT SUM(value) AS total_sum
   FROM posexplode(map("a", 1, "b", 2, "c", 3)) AS t(pos, key, value);
   +-----------+
   | total_sum |
   +-----------+
   | 6         |
   +-----------+
   ```
By the above example, you can better understand the usage and functionality of the `posexplode` function. In practical applications, you can expand and process array or map type data as needed.