Creating a Gin Index with Trigram (gin_trgm_ops) in Django model

Question

The new TrigramSimilarity feature of the django.contrib.postgres was great for a problem I had. I use it for a search bar to find hard to spell latin names. The problem is that

Answer 1

To make Django 2.2 use the index for icontains and similar searches:

Subclass GinIndex to make an case insensitive index (uppercasing all field values):

from django.contrib.postgres.indexes import GinIndex

class UpperGinIndex(GinIndex):

    def create_sql(self, model, schema_editor, using=''):
        statement = super().create_sql(model, schema_editor, using=using)
        quote_name = statement.parts['columns'].quote_name

        def upper_quoted(column):
            return f'UPPER({quote_name(column)})'
        statement.parts['columns'].quote_name = upper_quoted
        return statement

Add the index to your model like this, including kwarg name which is required when using opclasses:

class MyModel(Model):
    name = TextField(...)

    class Meta:
        indexes = [
            UpperGinIndex(fields=['name'], name='mymodel_name_gintrgm', opclasses=['gin_trgm_ops'])
        ]

Generate the migration and edit the generated file:

# Generated by Django 2.2.3 on 2019-07-15 10:46
from django.contrib.postgres.operations import TrigramExtension  # <<< add this
from django.db import migrations
import myapp.models


class Migration(migrations.Migration):

    operations = [
        TrigramExtension(),   # <<< add this
        migrations.AddIndex(
            model_name='mymodel',
            index=myapp.models.UpperGinIndex(fields=['name'], name='mymodel_name_gintrgm', opclasses=['gin_trgm_ops']),
        ),
    ]