EXPLODE_MAP_OUTER

Description

The explode_map_outer table function accepts a map type and expands the map into multiple rows, each containing a key-value pair. It should be used together with LATERAL VIEW.

Syntax

EXPLODE_MAP_OUTER(<map>)

Parameters

• <map> MAP type.

Return Value

• Returns a single-column, multi-row result composed of all elements in <map>. The column type is Nullable<Struct<K, V>>.
• If <map> is NULL or empty, 1 row with NULL is returned.

Examples

0. Prepare data
   create table example(
       k1 int
   ) properties(
       "replication_num" = "1"
   );
   
   insert into example values(1);

1. Regular parameters
   select  * from example lateral view explode_map_outer(map("k", "v", "k2", 123, null, null)) t2 as c;

   +------+-----------------------------+
   | k1   | c                           |
   +------+-----------------------------+
   |    1 | {"col1":"k", "col2":"v"}    |
   |    1 | {"col1":"k2", "col2":"123"} |
   |    1 | {"col1":null, "col2":null}  |
   +------+-----------------------------+

2. Expand key-value pairs into separate columns
   select  * from example lateral view explode_map_outer(map("k", "v", "k2", 123, null, null)) t2 as k, v;

   +------+------+------+
   | k1   | k    | v    |
   +------+------+------+
   |    1 | k    | v    |
   |    1 | k2   | 123  |
   |    1 | NULL | NULL |
   +------+------+------+

3. Empty object
   select  * from example lateral view explode_map_outer(map()) t2 as c;

   +------+------+
   | k1   | c    |
   +------+------+
   |    1 | NULL |
   +------+------+

4. NULL parameter
   select  * from example lateral view explode_map_outer(cast('ab' as map<string,string>)) t2 as c;

   +------+------+
   | k1   | c    |
   +------+------+
   |    1 | NULL |
   +------+------+