Advanced Database Setups

Here we cover details about more advanced database setups that might impact how you use triggers.

Multiple Databases

Triggers are migrated for multiple database just like models. If you define a custom router, triggers will be installed based on allow_migrate. See the the Django docs on multiple databases for more info.

Warning

If you migrate triggers and afterwards change the behavior of the router's allow_migrate, you risk having orphaned triggers installed on tables.

The management commands and core installation functions work the same way, targetting an individual database like Django's migrate command. Each command can be supplied with a -d or --database option.

For example, python manage.py pgtrigger install --database other will install all of the triggers on the other database.

If allow_migrate ignores a particular model for a database, the installation status will show as UNALLOWED when using python manage.py pgtrigger ls.

Note

If you've configured settings.INSTALL_ON_MIGRATE, triggers will be installed for the same database as the migrate command.

Dynamic runtime functions pgtrigger.ignore, pgtrigger.schema, and pgtrigger.constraints operate on all postgres databases at once unless the databases argument is provided.

Schemas

There are two common ways of using Postgres schemas in Django, both of which work with django-pgtrigger:

Create a database in settings.DATABASES for each schema, configuring the search_path in the OPTIONS.
Use an app like django-tenants to dynamically set the search_path for a single database.

When using the first approach, use the multi-database support detailed in the previous section. For the second approach, django-pgtrigger comes with the following functionality to dynamically set the search_path:

Pass --schema (-s) arguments for management commands. For example, this sets search_path to myschema,public and shows trigger installation status relative to those schemas:
```
python manage.py pgtrigger ls -s my_schema -s public
```

Programmatically set the search path with pgtrigger.schema. For example, this sets the search_path to myschema,public:

with pgtrigger.schema("myschema", "public"):
    # seach_path is set to "myschema,public". Any nested invocations of
    # pgtrigger.schema will append to the path if not currently
    # present

Note

If you find yourself wrapping the django-pgtrigger API with pgtrigger.schema, open an issue and let us know about your use case. We may consider making it a first-class citizen in the API if it's common.

The final thing to keep in mind with multi-schema support is that pgtrigger.ignore uses a special Postgres function for ignoring triggers that's installed under the public schema. The function is always referenced with a fully-qualified name.

If you don't use the public schema, configure the schema with settings.PGTRIGGER_SCHEMA. Setting this to None uses a relative path when installing and calling the function.

Partitions

django-pgtrigger supports tables that use Postgres table partitioning with no additional configuration.

Note

Row-level triggers are only available for partitioned tables in Postgres 13 and above. Triggers cannot be installed or uninstalled on a per-partition basis. Installing a trigger on a partitioned table installs it for all partitions.