Mercurial > kallithea
changeset 8589:7b0aafc6b7ca
mysql: create database with explicit UTF-8 character set and collation
A spin-off from Issue #378.
In MySQL, the character sets for server, database, tables, and connection are
set independently. Ideally, they should all use UTF-8, but systems tend to use
latin1 as default encoding, for example:
character_set_server = latin1
collation_server = latin1_swedish_ci
Databases would thus by default be created as:
character_set_database = latin1
collation_database = latin1_swedish_ci
To make things work consistently anyway, we have so far specified the utf8mb4
charset explicitly when creating tables, but there is no corresponding simple
option for specifying the collation for tables. We need a better solution.
If necessary and possible, the system charset and collation should be set to
UTF-8. Some systems already have these defaults default - see
https://mariadb.com/kb/en/differences-in-mariadb-in-debian-and-ubuntu/ .
The defaults can be changed as described on
https://mariadb.com/kb/en/setting-character-sets-and-collations/#example-changing-the-default-character-set-to-utf-8
to give something like:
character_set_server = utf8mb4
collation_server = utf8mb4_unicode_ci
Databases will then by default be created as:
character_set_database = utf8mb4
collation_database = utf8mb4_unicode_ci
and there is thus no longer any need for specifying the charset when creating
tables.
To be reasonably resilient across all systems without relying on system
defaults, we will now start specifying the charset and collation when creating
the database, but drop the specification of charset when creating tables.
For existing databases, it is recommended to change encoding (and collation) by
altering the database and each of the tables inside it as described on
https://stackoverflow.com/questions/6115612/how-to-convert-an-entire-mysql-database-characterset-and-collation-to-utf-8 .
Note the use of utf8mb4_unicode_ci instead of utf8mb4_general_ci - see
https://stackoverflow.com/questions/766809/whats-the-difference-between-utf8-general-ci-and-utf8-unicode-ci .
For investigation of these issues, consider the output from:
show variables like '%char%';
show variables like '%collation%';
show create database `KALLITHEA_DB_NAME`;
SELECT * FROM information_schema.SCHEMATA WHERE schema_name = "KALLITHEA_DB_NAME";
SELECT * FROM information_schema.TABLES T, information_schema.COLLATION_CHARACTER_SET_APPLICABILITY CCSA WHERE CCSA.collation_name = T.table_collation AND T.table_schema = "KALLITHEA_DB_NAME";
| author | Mads Kiilerich <mads@kiilerich.com> |
|---|---|
| date | Mon, 15 Jun 2020 17:27:19 +0200 |
| parents | 210e76d69b62 |
| children | e1f233b069b0 |
| files | kallithea/lib/db_manage.py kallithea/model/db.py |
| diffstat | 2 files changed, 1 insertions(+), 2 deletions(-) [+] |
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--- a/kallithea/lib/db_manage.py Mon Jun 15 16:57:20 2020 +0200 +++ b/kallithea/lib/db_manage.py Mon Jun 15 17:27:19 2020 +0200 @@ -97,7 +97,7 @@ engine = sqlalchemy.create_engine(url) with engine.connect() as conn: conn.execute('DROP DATABASE IF EXISTS `%s`' % database) - conn.execute('CREATE DATABASE `%s`' % database) + conn.execute('CREATE DATABASE `%s` CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci' % database) elif url.drivername == 'postgresql': from psycopg2.extensions import ISOLATION_LEVEL_AUTOCOMMIT url.database = 'postgres' # connect to the system database (as the real one might not exist)