Elena Stepanova added a comment - 2017-06-15 22:05 - edited Thanks for the report. JSON_MERGE complains about the empty array: MariaDB [test]> SELECT JSON_MERGE( '[]' , '{"c":"d"}' ); + -------------------------------+ | JSON_MERGE( '[]' , '{"c":"d"}' ) | + -------------------------------+ | NULL | + -------------------------------+ 1 row in set , 1 warning (0.00 sec)   MariaDB [test]> SHOW WARNINGS; + ---------+------+--------------------------------------------------------------------------------+ | Level | Code | Message | + ---------+------+--------------------------------------------------------------------------------+ | Warning | 4038 | Syntax error in JSON text in argument 1 to function 'json_merge' at position 2 | + ---------+------+--------------------------------------------------------------------------------+ 1 row in set (0.00 sec) But JSON_VALID says it's okay: MariaDB [test]> SELECT JSON_VALID( '[]' ); + ------------------+ | JSON_VALID( '[]' ) | + ------------------+ | 1 | + ------------------+ 1 row in set (0.00 sec)

Steven WdV added a comment - 2017-09-11 14:43 - edited Relates to / duplicate of MDEV-13324 . EDIT: maybe actually the other way around.