Add more documentation

docs/operations/data_migration.md

@@ -697,3 +697,30 @@ Example: `cf ssh getgov-za`
 |   | Parameter                  | Description                                                                 |
 |:-:|:-------------------------- |:----------------------------------------------------------------------------|
 | 1 | **debug**                  | Increases logging detail. Defaults to False.                                |
+
+## Transfer federal agency script
+The transfer federal agency script adds the "federal_type" field on each associated DomainRequest, and uses that to populate the "federal_type" field on each FederalAgency.
+
+**Important:** When running this script, note that data generated by our fixtures will be inaccurate (since we assign random data to them). Use real data on this script.
+Do note that there is a check on record uniqueness. If two or more records do NOT have the same value for federal_type for any given federal agency, then the record is skipped. This protects against fixtures data when loaded with real data.
+
+### Running on sandboxes
+
+#### Step 1: Login to CloudFoundry
+```cf login -a api.fr.cloud.gov --sso```
+
+#### Step 2: SSH into your environment
+```cf ssh getgov-{space}```
+
+Example: `cf ssh getgov-za`
+
+#### Step 3: Create a shell instance
+```/tmp/lifecycle/shell```
+
+#### Step 4: Running the script
+```./manage.py transfer_federal_agency_type```
+
+### Running locally
+
+#### Step 1: Running the script
+```docker-compose exec app ./manage.py transfer_federal_agency_type```

src/registrar/management/commands/transfer_federal_agency_type.py

@@ -18,7 +18,7 @@ class Command(BaseCommand, PopulateScriptTemplate):
     def handle(self, **kwargs):
         """Loops through each valid User object and updates its verification_type value"""
 
-        # Get all existing domain requests
+        # Get all existing domain requests. Select_related allows us to skip doing db queries.
         self.all_domain_requests = DomainRequest.objects.select_related("federal_agency").distinct()
         self.mass_update_records(
             FederalAgency, filter_conditions={"agency__isnull": False}, fields_to_update=["federal_type"]
@@ -28,9 +28,11 @@ class Command(BaseCommand, PopulateScriptTemplate):
         """Defines how we update the federal_type field on each record."""
         request = self.all_domain_requests.filter(federal_agency__agency=record.agency).first()
         record.federal_type = request.federal_type
-    
+
     def should_skip_record(self, record) -> bool:  # noqa
         """Defines the conditions in which we should skip updating a record."""
-        request = self.all_domain_requests.filter(federal_agency__agency=record.agency).first()
-        return not request or not request.federal_agency
+        requests = self.all_domain_requests.filter(federal_agency__agency=record.agency, federal_type__isnull=False)
+        # Check if all federal_type values are the same. Skip the record otherwise.
+        distinct_federal_types = requests.values('federal_type').distinct()
+        return distinct_federal_types.count() != 1