# Using GeneratedField with Postgres **URL:** \ **Category:** ORM\ **Created:** [January 20, 2024, 5:34pm UTC](https://forum.djangoproject.com/t/using-generatedfield-with-postgres/27224 "2024-01-20T17:34:36Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![mdlattimore](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.djangoproject.com/mdlattimore/32/17623_2.png) [@mdlattimore](https://forum.djangoproject.com/u/mdlattimore)\ **Post date:** [January 20, 2024, 5:34pm UTC](https://forum.djangoproject.com/t/using-generatedfield-with-postgres/27224/1 "2024-01-20T17:34:37Z")
I have an app using the new (in Django 5) GeneratedField field. Here’s the model: ```auto class Artist(models.Model): first_name = models.CharField(max_length=50, verbose_name="First Name") middle_name = models.CharField(max_length=50, verbose_name="Middle Name", null=True, blank=True) last_name = models.CharField(max_length=50, verbose_name="Last Name") full_name = models.GeneratedField( expression=Concat("first_name", models.Value(" "), "middle_name", models.Value(" "),"last_name"), output_field=models.CharField(max_length=100), db_persist = True, verbose_name="Full Name" ) birth_year = models.IntegerField(verbose_name="Year of Birth") nationality = models.CharField(max_length=100, verbose_name="Nationality") def __str__ (self): return f"{self.full_name}" ``` When attempting to deploy to [Fly.io](http://Fly.io), the deployment fails with the error: `django.db.utils.ProgrammingError: generation expression is not immutable` which causes the the release command to fail. It looks like the GeneratedField is the culprit. If I remove the GeneratedField, the app deploys without error. According the the Model Field Reference, " PostgreSQL requires functions and operators referenced in a generated column to be marked as `IMMUTABLE` ." Is there a way to successfully use a GeneratedField with Postgres? ---
**Author:** ![felixxm](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.djangoproject.com/felixxm/32/2479_2.png) [@felixxm](https://forum.djangoproject.com/u/felixxm)\ **Post date:** [January 20, 2024, 6:06pm UTC](https://forum.djangoproject.com/t/using-generatedfield-with-postgres/27224/2 "2024-01-20T18:06:26Z")
PostgreSQL requires functions and operators referenced in a generated column to be marked as `IMMUTABLE`. Unfortunately, PostgreSQL’s `CONCAT` is not considered an immutable, that’s why in Django 5.1 we’ve changed the implementation of Django’s `Concat()` to use `||` > > > This also avoids casting string based expressions in Concat() on > PostgreSQL. ---
**Author:** ![mdlattimore](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.djangoproject.com/mdlattimore/32/17623_2.png) [@mdlattimore](https://forum.djangoproject.com/u/mdlattimore)\ **Post date:** [January 20, 2024, 6:51pm UTC](https://forum.djangoproject.com/t/using-generatedfield-with-postgres/27224/3 "2024-01-20T18:51:24Z")
Thanks for the info – certainly answers my question. Are you aware of a workaround pending the release of 5.1? I’m one of those “non-expert users” to whom Paolo refers. ---
**Author:** ![felixxm](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.djangoproject.com/felixxm/32/2479_2.png) [@felixxm](https://forum.djangoproject.com/u/felixxm)\ **Post date:** [January 20, 2024, 6:55pm UTC](https://forum.djangoproject.com/t/using-generatedfield-with-postgres/27224/4 "2024-01-20T18:55:10Z")
You can copy the new implementation of `Concat()` and `ConcatPair()` into your code, and use it instead of builtin version: > ---
**Author:** ![pauloxnet](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.djangoproject.com/pauloxnet/32/11021_2.png) [@pauloxnet](https://forum.djangoproject.com/u/pauloxnet)\ **Post date:** [January 20, 2024, 7:07pm UTC](https://forum.djangoproject.com/t/using-generatedfield-with-postgres/27224/5 "2024-01-20T19:07:29Z")
I wrote some articles about GeneratedField, and one specific for PostgreSQL with a text concatenation example [https://www.paulox.net/2023/11/24/database-generated-columns-part-2-django-and-postgresql/#a-calculated-concatenated-field](https://www.paulox.net/2023/11/24/database-generated-columns-part-2-django-and-postgresql/#a-calculated-concatenated-field) Let me know if it’s clear for you and if it solves your problem. ---
**Author:** ![mdlattimore](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.djangoproject.com/mdlattimore/32/17623_2.png) [@mdlattimore](https://forum.djangoproject.com/u/mdlattimore)\ **Post date:** [January 20, 2024, 9:14pm UTC](https://forum.djangoproject.com/t/using-generatedfield-with-postgres/27224/6 "2024-01-20T21:14:58Z")
Gentlemen, thank you so much for your help. I’ve tried both solutions. The good news is both do solve the deployment problem – the app deploys without error. However, when saving a model instance that uses a GeneratedField (using the Django Admin), I get a new error: ```auto IntegrityError at /admin/art/artist/add/ null value in column "full_name" of relation "art_artist" violates not-null constraint DETAIL: Failing row contains (10, Pablo, null, Picasso, null, 1889, Spanish). Request Method: POST Request URL: http://curated-arts.fly.dev/admin/art/artist/add/ Django Version: 5.0.1 Exception Type: IntegrityError Exception Value: null value in column "full_name" of relation "art_artist" violates not-null constraint DETAIL: Failing row contains (10, Pablo, null, Picasso, null, 1889, Spanish). Exception Location: /usr/local/lib/python3.12/site-packages/psycopg/cursor.py, line 732, in execute Raised during: django.contrib.admin.options.add_view Python Executable: /usr/local/bin/python Python Version: 3.12.1 Python Path: ['/code', '/usr/local/bin', '/usr/local/lib/python312.zip', '/usr/local/lib/python3.12', '/usr/local/lib/python3.12/lib-dynload', '/usr/local/lib/python3.12/site-packages'] Server time: Sat, 20 Jan 2024 20:56:41 +0000 ``` I assume the not null constraint is a default setting for GeneratedField? Is there a way to remove the not null constraint?