Question: I've added GIN index to my db

```
ALTER TABLE mtn_order
ADD COLUMN textsearchable_index_col tsvector
GENERATED ALWAYS AS (to_tsvector('english', coalesce(descr, '') || ' ' || coalesce(descrrep, ''))) STORED;
CREATE INDEX textsearch_idx ON mtn_order USING GIN (textsearchable_index_col);

```

and `textsearchable_index_col = SearchVectorField(null=True)` to my model and now when i'm trying to save new instance i get:

```
ProgrammingError at /order/create/
cannot insert into column "textsearchable_index_col"
DETAIL:  Column "textsearchable_index_col" is a generated column.

```

How to stop Django trying to write `None` to that field

Answer: 
You won't be able to add it as a field to your model, because Django will try to write values back to it.

You could annotate it on when you need to:

```
MyModel.objects.annotate(
    index_col=RawSQL('textsearchable_index_col', 
                     [], 
                     output_field=SearchVectorField()
)

```
Override the \_do\_insert and \_do\_update methods on the model:

```
class MTNOrder:

    def _do_insert(self, manager, using, fields, update_pk, raw):
        fields = [
            f for f in fields if f.attname not in ['textsearchable_index_col']
        ]
        return super()._do_insert(manager, using, fields, update_pk, raw)

    def _do_update(self, base_qs, using, pk_val, values, update_fields, forced_update):
        values = [
            value for value in values if value[0].attname not in ['textsearchable_index_col']
        ]
        return super()._do_update(base_qs, using, pk_val, values, update_fields, forced_update)

```

Reference: [make django not insert certain fields](https://stackoverflow.com/questions/42551476/make-django-not-insert-certain-fields)