MariaDB Character Encoding - mysql

Question

I have just started to port an older MySQL/Spring/Eclipselink project to MariaDB. I am encountering an issue with table creation that can be demonstrated as follows:
MariaDB [spasm]> CREATE TABLE Configuration (ID BIGINT NOT NULL, Attribute VARCHAR(190) NOT NULL UNIQUE, Value VARCHAR(255) NOT NULL, PRIMARY KEY (ID));
Query OK, 0 rows affected (0.07 sec)
MariaDB [spasm]> drop table Configuration;
Query OK, 0 rows affected (0.06 sec)
MariaDB [spasm]> CREATE TABLE Configuration (ID BIGINT NOT NULL, Attribute VARCHAR(255) NOT NULL UNIQUE, Value VARCHAR(255) NOT NULL, PRIMARY KEY (ID));
ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes
MariaDB [spasm]>
MariaDB [spasm]> show variables like '%char%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8mb4 |
| character_set_connection | utf8mb4 |
| character_set_database | utf8mb4 |
| character_set_filesystem | binary |
| character_set_results | utf8mb4 |
| character_set_server | utf8mb4 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)
I understand that this is related to character encoding, however I don't know how to manage/correct it?

Answer 1

The new default CHARACTER SET is utf8mb4. It is complaining about the UNIQUE index:
Attribute VARCHAR(255) NOT NULL UNIQUE
If you are hitting the limit because of trying to use CHARACTER SET utf8mb4. Then do one of the following (each has a drawback) to avoid the error:
⚈ Upgrade to 5.7.7 (MariaDB 10.2.2?) for 3072 byte limit -- your cloud may not provide this;
⚈ Change 255 to 191 on the VARCHAR -- you lose any values longer than 191 characters (unlikely?);
⚈ ALTER .. CONVERT TO utf8 -- you lose Emoji and some of Chinese;
⚈ Use a "prefix" index -- you lose some of the performance benefits.
Or... Stay with 5.6/5.5/10.1 but perform 4 steps to raise the limit to 3072 bytes:
SET GLOBAL innodb_file_format=Barracuda;
SET GLOBAL innodb_file_per_table=1;
SET GLOBAL innodb_large_prefix=1;
logout & login (to get the global values);
ALTER TABLE tbl ROW_FORMAT=DYNAMIC; -- (or COMPRESSED)