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docs: minor fixes to README.md #448

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merged 1 commit into from May 12, 2020
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docs: minor fixes to README.md #448

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17 changes: 9 additions & 8 deletions README.md
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Expand Up @@ -85,13 +85,13 @@ DATABASES = {
### Transaction management isn't supported

django-spanner always works in Django's default transaction behavior,
autocommit mode. There's no way to turn this off and control transactions
manually such as with `django.db.transaction.atomic()`.
`autocommit` mode. Transactions cannot be controlled manually with
calls like `django.db.transaction.atomic()`.

### `AutoField` generates random IDs

Spanner doesn't have a way to auto-generate primary key values. Instead,
django-spanner monkeypatches `AutoField` to generate a random UUID4. It
Spanner doesn't have support for auto-generating primary key values. Therefore,
django-spanner monkey-patches `AutoField` to generate a random UUID4. It
generates a default using `Field`'s `default` option which means `AutoField`s
will have a value when a model instance is created. For example:

Expand All @@ -103,15 +103,16 @@ will have a value when a model instance is created. For example:

To avoid [hotspotting](https://cloud.google.com/spanner/docs/schema-design#uuid_primary_key),
these IDs are not monotonically increasing. This means that sorting models by
id isn't guaranteed to return them in the order in which they were created.
ID isn't guaranteed to return them in the order in which they were created.

### `ForeignKey` constraints aren't created

django-spanner [doesn't create foreign key constraints](https://github.com/googleapis/python-spanner-django/issues/313).
Spanner doesn't support `ON DELETE CASCADE` when creating foreign-key constraints so
django-spanner [doesn't support foreign key constraints](https://github.com/googleapis/python-spanner-django/issues/313).

### Check constraints aren't supported

Spanner doesn't support CHECK constraints so one isn't created for
Spanner doesn't support `CHECK` constraints so one isn't created for
[`PositiveIntegerField`](https://docs.djangoproject.com/en/stable/ref/models/fields/#positiveintegerfield)
and [`CheckConstraint`](https://docs.djangoproject.com/en/stable/ref/models/constraints/#checkconstraint)
can't be used.
Expand All @@ -123,7 +124,7 @@ decimal values without the possibility of data loss.

### `Variance` and `StdDev` database functions aren't supported

Spanner doesn't have these functions.
Spanner doesn't support these functions.

### `Meta.order_with_respect_to` model option isn't supported

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