Tuesday, August 15, 2023

Re: Case-insensitive non-deterministic collation

Found a great article by Adam Johnson written in February ...

https://adamj.eu/tech/2023/02/23/migrate-django-postgresql-ci-fields-case-insensitive-collation/

Covers all the bases.

Thank you Adam

Cheers

Mike

On 7/08/2023 12:28 pm, Mike Dewhirst wrote:
On 6/08/2023 9:17 pm, Chetan Ganji wrote:

Thanks Chetan

I have seen that 'icu' and 'und-whatever...' in various places on the web - so it seems to be spreading - but I haven't had the brainspace to understand it yet.

I'll try an experiment with provider='C' and locale='C' because that is how most of my databases are already established. If that passes my tests I might move on to other things.

From what I can see, PostgreSQL are likely to deprecate citext as inelegant. That would be why Django has deprecated it.

Thanks again.

Mike

Check this out.
https://gist.github.com/hleroy/2f3c6b00f284180da10ed9d20bf9240a

# According to Django documentation, it's preferable to use non-deterministic collations
# instead of the citext extension for Postgres > 12.
# Example migation to create the case insensitive collation
class Migration(migrations.Migration):
operations = [
CreateCollation(
'case_insensitive',
provider='icu',
locale='und-u-ks-level2',
deterministic=False
)
]
# Example model using the new db_collation parameter introduced with Django 3.2
class Tag(models.Model):
name = models.CharField(max_length=50, db_collation='case_insensitive')
class Meta:
ordering = ['name']
def __str__(self):
return self.name

Regards,
Chetan Ganji
+91-900-483-4183


On Sun, Aug 6, 2023 at 12:32 PM Mike Dewhirst <miked@dewhirst.com.au> wrote:
On 5/08/2023 7:58 pm, Chetan Ganji wrote:
Hi Mike

RE: The primary use case is to establish case-insensitivity when checking names - including usernames, company names and abbreviations/acronyms. 

I dont know anything about db_collation.

Me neither

Below 4 lookups should solve most common scenarios.

Actually that was how I did it originally. I switched to using the PostgreSQL CI field because it is all done in the database - much faster - and my code is much reduced and therefore fewer possibilities for bugs etc.

Judging from the Django release notes and the PostgreSQL docs there should be a straightforward answer to my question. Researching the correct answer is complex enough to make me ask here first.

Cheers

Mike


On Sat, Aug 5, 2023 at 1:35 PM Mike Dewhirst <miked@dewhirst.com.au> wrote:
The following warning triggered a bit of research which looks like a significant amount of study will be required to find the collation needed ...


django.contrib.postgres.fields.CICharField is deprecated. Support for it (except in historical migrations) will be removed in Django 5.1.
        HINT: Use CharField(db_collation="…") with a case-insensitive non-deterministic collation instead.


Does anyone have experience they would like to share? What replaces that ellipsis?

The primary use case is to establish case-insensitivity when checking names - including usernames, company names and abbreviations/acronyms. Maybe there is a better way to handle that?

This is my typical PostgreSQL database spec ...

CREATE DATABASE xxxx
    WITH
    OWNER = miked
    ENCODING = 'UTF8'
    LC_COLLATE = 'C'
    LC_CTYPE = 'C'
    TABLESPACE = pg_default
    CONNECTION LIMIT = -1
    IS_TEMPLATE = False;

Many thanks for any help

Cheers

Mike

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