DataFusion Query Federation for Agentic APIs

An agentic data API should not be a polite wrapper around unlimited SQL.

Agentic APIs need query boundaries

Agentic APIs turn data access into a runtime contract. The API has to decide which sources are visible, which functions are allowed, which policies apply, and how the result should be explained. If the interface only exposes "run this SQL," the agent inherits every ambiguity in the data platform.

Apache DataFusion matters because it is a query engine and framework with extension points. It can work with catalogs, schemas, tables, custom table providers, expressions, functions, and logical plans. That makes it a useful substrate for governed query services when teams want control over the interface rather than only a connection string.

DataFusion exposes extension points

DataFusion documentation describes catalogs, schemas, and tables, plus custom table providers for integrating new data sources. That is where a query service can make federation explicit. A custom provider can represent a governed source. A catalog can name the boundary. A logical plan can be inspected before execution.

The claim is not that DataFusion magically solves federation. Federation is still architecture work. The value is that the architecture can be built from inspectable components instead of hidden behind a proprietary black box.

Federation needs control

For related ODI patterns, read DataFusion session boundaries, DataFusion logical plans as policy evidence, and agentic AI tool schemas and data contracts.

The API should log the request, selected sources, rejected sources, policy decision, logical plan, cost estimate, and output lineage. That is the difference between a helpful query service and a production incident with a nice JSON response.

What breaks first

• The API federates sources but loses source-specific policy context.
• UDFs enter the runtime without ownership, versioning, or review.
• The query result is logged, but the plan that produced it is not.
• Agents receive the same endpoint humans use, with no narrower contract.

API design questions

Ask which catalog objects are exposed, which table providers are trusted, which functions are allowed, and which plan checks run before execution. The answers should be in code and logs, not in a meeting note.

Sources to start with

These primary sources anchor the technical claims in this guide.

• Apache DataFusion documentation
• DataFusion catalogs, schemas, and tables documentation
• DataFusion custom table provider documentation
• OpenLineage object model documentation

Agents should query through contracts, not through hope dressed up as an endpoint.