CONCAT to update db text field

I needed to collect messages from different processes which was triggered by a record insertion. To keep things simple and denormalized, this stack overflow gem allows for that.

from django.db import models

class DBModel(models.Model):
    @classmethod
    def append_text(cls, event_id, text_field, message)
        cls.objects.filter(id=event_id).update(
            text_field=Concat(text_field, Value(message))
        )

Using the database function CONCAT, it offloads serializability to the database guaranteeing no race conditions.

Concat(ConcatPair(F(text_field), Value(message)))

Using F methods, it simply appends message to the existing field.

Happy hackin’!

Reference:

• Can I use Django F() objects with string concatenation?

• MySQL: Concat

• MySQL: Isolation levels