Core Graph

Core graph

What this is

The core/graph package contains a reusable graph which the Application and Automation Builder (in contrib/builder and contrib/automation respectively) rely on.

In the Application Builder, it is used to manage and traverse the relationship between Element.

In the Automation Builder, it is used to manage and traverse the relationship between AutomationNode.

Core abstractions

• A graph is made up of points. This term is deliberately abstract — what a point represents varies between modules (see "How X Builder uses it" sections below).
• An edge connects points. Edge semantics also vary per module (see "How X Builder uses it" sections below).
• Points can be traversed to determine the "next", "previous", and "parent" points.
• The graph itself is a JSON object.
• The graph is stored on a Django container model that implements GraphModelMixin. Individual point models implement GraphPointMixin, which provides helpers for traversal, parent access, edge labels, etc.
• An empty string ("") consistently represents the default/fallback edge throughout the system — in edge dictionaries, in children maps, and in migration from legacy formats.

Design principles

• core/graph must remain module-agnostic. No references to Element, AutomationNode, or any other module-specific concept should appear in core/graph code.
• Push module-specific logic out. If a feature in the Application or Automation Builder has requirements specific to that module, the reusable parts belong in core/graph and the module-specific code belongs in the consuming module.

Key files

• src/baserow/core/graph/ - the directory containing the graph system.
• tests/baserow/core/graph/ - the directory for all backend graph system tests.
• src/baserow/core/graph/handler.py — contains the BaseGraphHandler
• src/baserow/core/graph/models.py — contains the two Django Model mixins.

How Application Builder uses it

• The container model is Page; the point model is Element.
• Most points won't have an edge, it'll just be a blank string. If, however, the element's parent implements ContainerElementTypeMixin, then its edge is the element's place_in_container. For example:
  • element1 is a ColumnElement (so its type is ColumnElementType, which implements ContainerElementTypeMixin). This column has column_amount=3.
  • element2 is a HeadingElement. We want it in the second column. We will make its parent element1, and set its place_in_container to "1".
• At the moment, there is at most one edge between elements, and it's always a string (whether blank, or a numeric place_in_container).

How Automation Builder uses it

• The container model is AutomationWorkflow; the point model is AutomationNode.
• Points in automation builder can have one or more edges. They can be found by fetching the service, and calling get_edges. For example:
  • node1 is an AutomationNode.
  • service1 = node1.service.specific.get_type() gives me node1's service type.
  • service1.get_edges() returns a dictionary defining the edges between my nodes.
  • Most node services get_edges calls will return {"": {"label": ""}}. This represents a straight traversal without an edge name — the outer dictionary key of "" is the default-edge convention (see Core abstractions). The label in the inner dictionary is a user-configured label they can see in the UI.
  • The CoreRouterServiceType however will return a UUID for the outer dictionary key, for each edge the user has configured, and a default edge (which is the fallback). E.g.
    • {"condition1Uuid": {"label": "Condition1"}, "condition2Uuid": {"label": "Condition2"}, "": {"label": "Default fallback"}}

Common operations

• Given a container model instance, call .get_graph() to get the graph handler. This is the standard entry point for inserting, removing, or moving points. Example: page.get_graph() in the Application Builder, workflow.get_graph() in the Automation Builder.
• Given a point model instance, the GraphPointMixin methods provide traversal helpers (next/previous/parent), edge label access, and related operations. Prefer these over hand-rolling traversal logic.

Common pitfalls

• In the graph, children does not contain all child points, only the "first" child of the container. To find all children, you must choose that first child point, and then keep traversing next until no points remain.
• It is possible to run into a "legacy" children that looks like this: {"children": [7]}. The BaseGraphHandler will support this, and migrate it to the new format: {"children": {"": [7]}} (the "" key follows the default-edge convention described in Core abstractions).

Testing

• Ensure any handler modifications are tested in its test file, test_graph_handler.py.
• Ensure any model mixin modifications are tested in their test file, test_graph_models.py.
• Test fixtures and configuration can be found in the test directory's fixtures.py and conftest.py.