![]() ![]() The application was highly parallelism - this had to be handled in the database. To add insult to the injury, PostgreSQL had all these.Ĭreating some workaround on the client side was no option. No, MySQL doesn't allow creating indexes on views. Nope, MySQL doesn't allow conditional indexes. Keep the constraint but replace the parent in the index with a computed column.Pity me for my weakness for I was like a thirsty fool in the desert. You see, I was using an ORM and I really liked the convenience of the ForeignKey field. This is something normal in SQL and ideally you'd redesign the model and MySQL is not to be blamed, right? But, alas, no. Given unfavorable conditions (parallelism), get_or_create would create duplicate objects - because the database lets it. create ( name = "stuff", type = "foobar" ). If this is the same with the migration system in 1.7 (seems it it, but you only get a plain traceback) then it's ideal to have migrations small in scope if you have custom sql that can easily fail, and squash them later, after you have successfully ran them. ! like to gently persuade you to consider a slightly ! The South developers regret this has happened, and would ! to leave it in an interim state between migrations. ! schema-altering statements in transactions, we have had ! Since you have a database that does not support running ! Error found during real run of migration! Aborting. Thus, migrations in MySQL must be approached with great care (test them well) and to avoid downtime you need to use specific external tools. The almighty InnoDB can't save your sanity when an ALTER is used in a transaction. ĭDL statements in MySQL, not only they are slow and lock tables (that means downtime), they will ignore transactions. ![]() Note that this will take long time to run (MySQL seems to copy all the tables for some reason) and it will change the encoding and collation for all the columns. Migration ): dependencies = operations = raise RuntimeError ( "This migration probably took 2 hours, you don't really want to rollback. execute ( "ALTER TABLE %s CONVERT TO CHARACTER SET utf8 COLLATE utf8_bin" % table ) def backwards ( self, orm ): # Altering the tables takes lots of time and # locks the tables, since it copies all the data. fetchall (): print ( ' Altering table %s. execute ( "SHOW TABLES " ) for table, in cursor. ![]() execute ( "ALTER DATABASE CHARACTER SET utf8 COLLATE utf8_bin " ) cursor. cursor () as cursor : print ( '' ) print ( ' Altering database. The settings now look like this:įrom django.db import migrations def forwards ( apps, schema_editor ): with schema_editor. The solution is to use utf_bin collation and specify a different one only when you need special accent handling and case folding. You'll notice that get_or_create doesn't work as expected when you have accents or a different case. If you have a case insensitive collation all sorts of queries that aren't a text search will behave strangely. This means your queries and indexes are also going to be case insensitive. | utf32 | UTF-32 Unicode | utf32_general_ci | 4 |Īll the default collations are case insensitive. | utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 | | utf8 | UTF-8 Unicode | utf8_general_ci | 3 | | ascii | US ASCII | ascii_general_ci | 1 | ![]() | latin1 | cp1252 West European | latin1_swedish_ci | 1 | | Charset | Description | Default collation | Maxlen | Notice a pattern here? Note the _ci suffix: A collation is a set of rules for comparing characters in a character set. īut that's not that bad, you should get some errors if you fail to set the correct encoding. But that means smaller index, only 191 characters. If you need to store emoticons like an angry face □- and most probably you'd want to, given the predicament - then you're out of luck, you need a different charset, utf8mb4. Yes, the index on utf8 columns is limited to 255 characters. CharField ( max_length = 255, db_index = True ) ![]()
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