Save real data type in addition to existing data type

Saving "real" data type

Data type are actually not the "real" data type, but "storage" data type.
Storing an additional byte in frm files to save "real" data type information would solve lots of issues.

BOOLEAN type means something compare to storage data type BIT(1) : that means Connector may return true/false and not 0/1.
JSON type means that data is not just a string, but that string can be a parse to JSON object.

Connectors actually don't know the "real" data type, and it's needed.
Example with JSON: MySQL server save JSON field differently. The result is having a dedicated MYSQL_TYPE_JSON Data type that is sent to connectors.
Connectors may then handle the data differently. The most popular javascript driver use that information to create a JSON object from the string.

connection.query("insert into user(name, additional) value (?, ?)", ['john', {game:'myGame', level:23}]);

connection.query("select from user", (err, rows) => {

	//with mysql

        //rows[0] = {name:'john', additional: {game:'myGame', level:23}}

	//with mariadb :

        //rows[0] = {name:'john', additional: "{game:'myGame', level:23}"}

});

MariaDB saves JSON like a string, then connector has no information that this field is a JSON object.

That additional byte would permit a lot of new functionalities: BOOLEAN, JSON ok, but that may permit new types like IPV4 / IPV6 / UUID that are store are text.

Another minor annoyance is that SHOW CREATE could return initial type :

CREATE TABLE `jsondata` (val1 JSON);

SHOW CREATE TABLE `testj`.`jsondata`;

//=> CREATE TABLE `jsondata` (

  `val1` longtext CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=utf8

//=> information about JSON is lost

Possible non breaking change of protocol

Current protocol for Column definition packet is :

string<lenenc> catalog (always 'def')

string<lenenc> schema

string<lenenc> table alias

string<lenenc> table

string<lenenc> column alias

string<lenenc> column

int<lenenc> length of fixed fields (=0xC)

int<2> character set number

int<4> max. column size

int<1> Field types

int<2> Field detail flag

int<1> decimals

int<2> - unused -

First field always send string<lenenc> catalog (always 'def') = 0x03 0x64 0x65 0x66
no driver does use this information, because catalog doesn't exist in Mariadb.

This field can be used to transmit to driver this additional metadata byte.
This would permit that existing driver will receive the "storage" data type