Denormalized `pgh_context` does not get written to event table

[gary-pinata]

Thank you for this library and for pgtrigger. Both excellent libraries!

I am currently have a multi-database setup using a "default" db router and another db router (which we'll call "other" for the purposes of this issue). I have the trigger functions installed in my second database.

My pghistory related settings are as follows:

INSTALL_ON_MIGRATE = True
PGHISTORY_ADMIN_ALL_EVENTS = False
PGHISTORY_APPEND_ONLY = True

# See https://django-pghistory.readthedocs.io/en/stable/event_models/#denormalizing-context
# Note: Currently `pgh_obj` field and `pgh_context_id` field have to be set in pghistory.track decorator if
#       you want it to be None
# PGHISTORY_CONTEXT_FIELD = None
# PGHISTORY_OBJ_FIELD = None

My routers are along these lines ...

Default database:

class DefaultRouter:
    """
    A router to control all database operations on all models in all applications _except_ other.
    """

    db = "default"
    route_everything_but_these_app_labels = {
        "other",
    }

    def db_for_read(self, model, **hints):
        """
        Attempts to read all models, _except_ other models, go to default db.
        """
        if model._meta.app_label not in self.route_everything_but_these_app_labels:
            return self.db
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write all models, _except_ other models, go to default db.
        """
        if model._meta.app_label not in self.route_everything_but_these_app_labels:
            return self.db
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """
        Allow relations if a model in other is _not_ involved.
        """
        if (
            obj1._meta.app_label not in self.route_everything_but_these_app_labels
            and obj2._meta.app_label not in self.route_everything_but_these_app_labels
        ):
            return True
        return None

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        Make sure all apps, _except_ other, only appear in the default database.
        """
        if app_label not in self.route_everything_but_these_app_labels:
            return db == self.db
        return None

"other" database:

class OtherRouter:
    """
    A router to control all database operations on models in the other application.
    """

    db = "other"
    route_app_labels = {
        "other",
        # "pghistory",
        # # Note: "pghistory" is installed as part of the default database
    }

    def db_for_read(self, model, **hints):
        """
        Attempts to read from other models go to other db.
        """
        if model._meta.app_label in self.route_app_labels:
            return self.db
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write to other models go to other db.
        """
        if model._meta.app_label in self.route_app_labels:
            return self.db
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """
        Allow relations if both models are in the `route_app_labels`.
        """
        if obj1._meta.app_label in self.route_app_labels and obj2._meta.app_label in self.route_app_labels:
            return True
        return None

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        Make sure the other apps appear in the other db.
        """
        if app_label in self.route_app_labels:
            return db == self.db
        return None

These are both added to the DATABASES settings, with "default" first.

My model is along these lines ...

@pghistory.track(
    pghistory.InsertEvent(),
    pghistory.UpdateEvent(),
    pghistory.DeleteEvent(),
    context_field=pghistory.ContextJSONField(),
    context_id_field=None,
    obj_field=None,
)
class Capability(AbstractBareBonesModel, PubIdMixin, EnabledMixin, NameMixin):
    pass

When I insert using SQL or through the Python shell, the corresponding event record is inserted into the proper event table.

When I do the following via the Django shell, it is inserted, but the pgh_context field is not set (it remains null).

import pghistory
import ulid
from django.utils import timezone
from blah.apps.other.models.blah import Capability

capability = None

with pghistory.context(test_key0="test value 0"):
    capability = Capability.objects.create(
        enabled=False,
        start_at=timezone.now(),
        internal_name="TEST",
        display_name="testing 123",
        pub_id=ulid.new(),
    )

capability.__dict__
# everything is correct in the db _except_ `pgh_context`

with pghistory.context(test_key1="test value 1"):
    capability.display_name = "Testing 123"
    capability.save()

capability.refresh_from_db()
capability.__dict__
# everything is correct in the db _except_ `pgh_context`

with pghistory.context(test_key2="test value 2"):
    capability.enabled = True
    capability.save()

capability.refresh_from_db()
capability.__dict__
# everything is correct in the db _except_ `pgh_context`

From an initial investigation (by overriding pghistory.context), it appears that the with clauses are being executed with the expected key/value combination. It further appears that _inject_history_context is not being invoked (or, if it is, is not having the intended effect).

What am I doing wrong?

[gary-pinata]

PS I'm using the following versions:

    "django-pgtrigger==4.15.4",
    "django-pghistory==3.8.3",