在Django中区分大小写的搜索，但在Mysql中被忽略

Question

I have a field in a Django Model for storing a unique (hash) value. Turns out that the database (MySQL/inno) doesn't do a case sensitive search on this type (VARCHAR), not even if I explicitly tell Django to do a case sensitive search Document.objects.get(hash__exact="abcd123") . So "abcd123" and "ABcd123" are both returned, which I don't want.

class document(models.Model):
   filename    = models.CharField(max_length=120)
   hash        = models.CharField(max_length=33 )

I can change the 'hash field' to a BinaryField , so in the DB it becomes a LONGBLOB , and it does do a case-sensitive search (and works). However, this doesn't seem very efficient to me. Is there a better way (in Django) to do this, like adding 'utf8 COLLATE'? or what would be the correct Fieldtype in this situation? (yes, I know I could use PostgreSQL instead..)

Answer 1

The default collation for character set for MySQL is latin1_swedish_ci, which is case insensitive. Not sure why that is. But you should create your database like so:

CREATE DATABASE database_name CHARACTER SET utf8;

Answer 2

As @dan-klasson mentioned, the default non-binary string comparison is case insensetive by default ; notice the _ci at the end of latin1_swedish_ci , it stands for case-insensetive. You can, as Dan mentioned, create the database with a case sensitive collation and character set.

You may be also interested to know that you can always create a single table or even set only a single column to use a different collation (for the same result). And you may also change these collations post creation, for instance per table:

ALTER TABLE documents__document CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;

Additionally, if you rather not change the database/table charset/collation, Django allows to run a custom query using the raw method . So you may be able to work around the change by using something like the following, though I have not tested this myself:

Document.objects.raw("SELECT * FROM documents__document LIKE '%s' COLLATE latin1_bin", ['abcd123'])

Answer 3

You got case sensitive filter query wrong. It should be __exact , like this:

Document.objects.get(hash__exact="abcd123")

And for case insensitive filter query, you need to use __iexact .