set hive.fetch.task.conversion=more;

DESCRIBE FUNCTION coalesce;
DESCRIBE FUNCTION EXTENDED coalesce;

EXPLAIN
SELECT COALESCE(1),
       COALESCE(1, 2),
       COALESCE(NULL, 2),
       COALESCE(1, NULL),
       COALESCE(NULL, NULL, 3),
       COALESCE(4, NULL, NULL, NULL),
       COALESCE('1'),
       COALESCE('1', '2'),
       COALESCE(NULL, '2'),
       COALESCE('1', NULL),
       COALESCE(NULL, NULL, '3'),
       COALESCE('4', NULL, NULL, NULL),
       COALESCE(1.0),
       COALESCE(1.0, 2.0),
       COALESCE(NULL, 2.0),
       COALESCE(NULL, 2.0, 3.0),
       COALESCE(2.0, NULL, 3.0),
       COALESCE(IF(TRUE, NULL, 0), NULL)
FROM src tablesample (1 rows);

SELECT COALESCE(1),
       COALESCE(1, 2),
       COALESCE(NULL, 2),
       COALESCE(1, NULL),
       COALESCE(NULL, NULL, 3),
       COALESCE(4, NULL, NULL, NULL),
       COALESCE('1'),
       COALESCE('1', '2'),
       COALESCE(NULL, '2'),
       COALESCE('1', NULL),
       COALESCE(NULL, NULL, '3'),
       COALESCE('4', NULL, NULL, NULL),
       COALESCE(1.0),
       COALESCE(1.0, 2.0),
       COALESCE(NULL, 2.0),
       COALESCE(NULL, 2.0, 3.0),
       COALESCE(2.0, NULL, 3.0),
       COALESCE(IF(TRUE, NULL, 0), NULL)
FROM src tablesample (1 rows);

EXPLAIN
SELECT COALESCE(src_thrift.lint[1], 999),
       COALESCE(src_thrift.lintstring[0].mystring, '999'),
       COALESCE(src_thrift.mstringstring['key_2'], '999')
FROM src_thrift;

SELECT COALESCE(src_thrift.lint[1], 999),
       COALESCE(src_thrift.lintstring[0].mystring, '999'),
       COALESCE(src_thrift.mstringstring['key_2'], '999')
FROM src_thrift;