I am not using any library to access mariadb, I am just using the protocol directly as described here.

The issue is when creating a prepared statement (using the binary protocol).
COM_STMT_PREPARE_OK returns the wrong column type in the column description packet.

This only happens with mariadb 10.3.x. It works fine with 10.2.x and prior versions.

Details:

Table:

CREATE TEMPORARY TABLE test (

  id             serial    PRIMARY KEY,

  name           text      NOT NULL

);

Prepared statement:

INSERT INTO test (name) VALUES (?)

Protocol calls:

> <COM_STMT_PREPARE>

>  INSERT INTO test (name) VALUES (?)

< <COM_STMT_PREPARE_OK>

<  column count: 0

<  parameter count: 1

<  <COLUMN_DEFINITION>

<  schema: ""

<  table alias: ""

<  table: ""

<  column alias: "?"

<  column: ""

<  collation: 63

<  max column size: 0

<  column type: *0x06 = NULL instead of 0xfd = VARSTRING*

<  binary: true

<  decimals: 0

< <EOF>

There's only one column definition sent, since there's only one param in the statement.
The column definition now returns a column type of 0x06 (NULL).
With all previous versions (10.2.x and earlier), it returns 0xfd (VARSTRING), which is correct, it's the type of the name column.