Can you achieve a case insensitive 'unique' constraint in Sqlite3 (with Django)?

Question

So let\'s say I\'m using Python 2.5\'s built-in default sqlite3 and I have a Django model class with the following code:

class SomeEntity(models.Model):
    some         


        

Answer 1

Perhaps you can create and use a custom model field; it would be a subclass of CharField but providing a db_type method returning "text collate nocase"

Answer 2

Yes this can easily be done by adding a unique index to the table with the following command:

CREATE UNIQUE INDEX uidxName ON mytable (myfield COLLATE NOCASE)

If you need case insensitivity for nonASCII letters, you will need to register your own COLLATION with commands similar to the following:

The following example shows a custom collation that sorts “the wrong way”:

import sqlite3

def collate_reverse(string1, string2):
    return -cmp(string1, string2)

con = sqlite3.connect(":memory:")
con.create_collation("reverse", collate_reverse)

cur = con.cursor()
cur.execute("create table test(x)")
cur.executemany("insert into test(x) values (?)", [("a",), ("b",)])
cur.execute("select x from test order by x collate reverse")
for row in cur:
    print row
con.close()

Additional python documentation for sqlite3 shown here