Intra-data source Relationships

This is the official documentation of the forestadmin-agent-django and forestadmin-agent-flask Python agents.

We've seen that when building data sources, collections must fulfill the contract they defined when declaring their capabilities.

The same is also true for Intra-data source relationships which are declared on the structure of a collection: declared relations must be handled when processing filters, projection, and aggregations.

In practice

one-to-many and many-to-many relationships do not require additional work: Forest Admin will automatically call the destination collection with a valid filter.

On the other hand, many-to-one and one-to-one relationships require the implementer to make all fields from the target collection available on the source collection (under a prefix).

Example

If a structure declaration contains the following statement

from forestadmin.datasource_toolkit.collections import Collection

class MyCollection(Collection):
    def __init__(self, datasource):
        super().__init__("movies", datasource)

        #  [...]

        self.add_field("director", {
            "type": "ManyToOne",
            "foreign_collection": "people",
            "foreign_key": "directorId",
            "foreign_key_target": "id",
        })

Then the collection must accept references to fields from the people collection under the director prefix in all method parameters.

from forestadmin.datasource_toolkit.interfaces.query.condition_tree.nodes.branch import ConditionTreeBranch
from forestadmin.datasource_toolkit.interfaces.query.condition_tree.nodes.leaf import ConditionTreeLeaf
from forestadmin.datasource_toolkit.interfaces.query.filter.paginated import PaginatedFilter
from forestadmin.datasource_toolkit.interfaces.query.projections import Projection

# The following call is using both fields from the "movies" and "people" collection
await datasource.get_collection("movies").list(
    caller,
    PaginatedFilter(
        {
            "condition_tree": ConditionTreeBranch(
                aggregator="and",
                conditions=[
                    ConditionTreeLeaf(field="title", operator="Equal", value="E.T."),
                    ConditionTreeLeaf("director:firstName", "Equal", "Steven"),
                ],
            ),
            "sort": [{"field": "director:birthDate", "ascending": True}],
        }
    ),
    Projection("id", "title", "director:firstName", "director:lastName"),
)

should return

{
  "id": 34,
  "title": "E.T",
  "director": { "firstName": "Steven", "lastName": "Spielberg" }
}