JSON is an alias for LONGTEXT introduced for compatibility reasons with MySQL's JSON data type. MariaDB implements this as a LONGTEXT rather, as the JSON data type contradicts the SQL standard, and MariaDB's benchmarks indicate that performance is at least equivalent.

In order to ensure that a a valid json document is inserted, the JSON_VALID function can be used as a CHECK constraint. This constraint is automatically included for types using the JSON alias from MariaDB 10.4.3.

Examples

CREATE TABLE t (j JSON);

DESC t;
+-------+----------+------+-----+---------+-------+
| Field | Type     | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| j     | longtext | YES  |     | NULL    |       |
+-------+----------+------+-----+---------+-------+

With validation:

CREATE TABLE t2 (
  j JSON 
  CHECK (JSON_VALID(j))
);

INSERT INTO t2 VALUES ('invalid');
ERROR 4025 (23000): CONSTRAINT `j` failed for `test`.`t2`

INSERT INTO t2 VALUES ('{"id": 1, "name": "Monty"}');
Query OK, 1 row affected (0.13 sec)

Replicating JSON Data Between MySQL and MariaDB

The JSON type in MySQL stores the JSON object in a compact form, not as LONGTEXT as in MariaDB. This means that row based replication will not work for JSON types from MySQL to MariaDB.

There are a a few different ways to solve this:

• Use statement based replication.
• Change the JSON column to type TEXT in MySQL

Converting a MySQL TABLE with JSON Fields to MariaDB

MariaDB can't directly access MySQL's JSON format.

There are a a few different ways to move the table to MariaDB:

• Change the JSON column to type TEXT in MySQL. After this, MariaDB can directly use the table without any need for a dump and restore.
• Use mysqldump to copy the table.

Differences Between MySQL JSON Strings and MariaDB JSON Strings

• In MySQL, JSON is an object and is compared according to json values. In MariaDB JSON strings are normal strings and compared as strings. One exception is when using JSON_EXTRACT() in which case strings are unescaped before comparison.

See Also

• JSON Functions
• CONNECT JSON Table Type
• MDEV-9144