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README.md

🧠 ComputeEngine (WIP)

The ComputeEngine is Feast’s pluggable abstraction for executing feature pipelines — including transformations, aggregations, joins, and materializations/get_historical_features — on a backend of your choice (e.g., Spark, PyArrow, Pandas, Ray).

It powers both:

  • materialize() – for batch and stream generation of features to offline/online stores
  • get_historical_features() – for point-in-time correct training dataset retrieval

This system builds and executes DAGs (Directed Acyclic Graphs) of typed operations, enabling modular and scalable workflows.


🧠 Core Concepts

Component Description API
ComputeEngine Interface for executing materialization and retrieval tasks link
FeatureBuilder Constructs a DAG from Feature View definition for a specific backend link
FeatureResolver Resolves feature DAG by topological order for execution link
DAG Represents a logical DAG operation (read, aggregate, join, etc.) link
ExecutionPlan Executes nodes in dependency order and stores intermediate outputs link
ExecutionContext Holds config, registry, stores, entity data, and node outputs link

Feature resolver and builder

The FeatureBuilder initializes a FeatureResolver that extracts a DAG from the FeatureView definitions, resolving dependencies and ensuring the correct execution order.
The FeatureView represents a logical data source, while DataSource represents the physical data source (e.g., BigQuery, Spark, etc.).
When defining a FeatureView, the source can be a physical DataSource, a derived FeatureView, or a list of FeatureViews. The FeatureResolver walks through the FeatureView sources, and topologically sorts the DAG nodes based on dependencies, and returns a head node that represents the final output of the DAG.
Subsequently, the FeatureBuilder builds the DAG nodes from the resolved head node, creating a DAGNode for each operation (read, join, filter, aggregate, etc.). An example of built output from FeatureBuilder:

- Output(Agg(daily_driver_stats))
  - Agg(daily_driver_stats)
    - Filter(daily_driver_stats)
      - Transform(daily_driver_stats)
        - Agg(hourly_driver_stats)
          - Filter(hourly_driver_stats)
            - Transform(hourly_driver_stats)
              - Source(hourly_driver_stats)

Diagram

feature_dag.png

✨ Available Engines

🔥 SparkComputeEngine

{% page-ref page="spark.md" %}

  • Distributed DAG execution via Apache Spark
  • Supports point-in-time joins and large-scale materialization
  • Integrates with SparkOfflineStore and SparkMaterializationJob

⚡ RayComputeEngine (contrib)

  • Distributed DAG execution via Ray
  • Intelligent join strategies (broadcast vs distributed)
  • Automatic resource management and optimization
  • Integrates with RayOfflineStore and RayMaterializationJob
  • See Ray Compute Engine documentation for details

🧪 LocalComputeEngine

{% page-ref page="local.md" %}

  • Runs on Arrow + Specified backend (e.g., Pandas, Polars)
  • Designed for local dev, testing, or lightweight feature generation
  • Supports LocalMaterializationJob and LocalHistoricalRetrievalJob

🧊 SnowflakeComputeEngine

  • Runs entirely in Snowflake
  • Supports Snowflake SQL for feature transformations and aggregations
  • Integrates with SnowflakeOfflineStore and SnowflakeMaterializationJob

{% page-ref page="snowflake.md" %}

LambdaComputeEngine

{% page-ref page="lambda.md" %}


🛠️ Feature Builder Flow

SourceReadNode
      |
      v
TransformationNode (If feature_transformation is defined) | JoinNode (default behavior for multiple sources)
      |
      v
FilterNode (Always included; applies TTL or user-defined filters)
      |
      v
AggregationNode (If aggregations are defined in FeatureView)
      |
      v
DeduplicationNode (If no aggregation is defined for get_historical_features) 
      |
      v
ValidationNode (If enable_validation = True)
      |
      v
Output
  ├──> RetrievalOutput (For get_historical_features)
  └──> OnlineStoreWrite / OfflineStoreWrite (For materialize)

Each step is implemented as a DAGNode. An ExecutionPlan executes these nodes in topological order, caching DAGValue outputs.


🧩 Implementing a Custom Compute Engine

To create your own compute engine:

  1. Implement the interface
from feast.infra.compute_engines.base import ComputeEngine
from typing import Sequence, Union
from feast.batch_feature_view import BatchFeatureView
from feast.entity import Entity
from feast.feature_view import FeatureView
from feast.infra.common.materialization_job import (
    MaterializationJob,
    MaterializationTask,
)
from feast.infra.common.retrieval_task import HistoricalRetrievalTask
from feast.infra.offline_stores.offline_store import RetrievalJob
from feast.infra.registry.base_registry import BaseRegistry
from feast.on_demand_feature_view import OnDemandFeatureView
from feast.stream_feature_view import StreamFeatureView


class MyComputeEngine(ComputeEngine):
    def update(
        self,
        project: str,
        views_to_delete: Sequence[
            Union[BatchFeatureView, StreamFeatureView, FeatureView]
        ],
        views_to_keep: Sequence[
            Union[BatchFeatureView, StreamFeatureView, FeatureView, OnDemandFeatureView]
        ],
        entities_to_delete: Sequence[Entity],
        entities_to_keep: Sequence[Entity],
    ):
        ...
   
    def _materialize_one(
        self,
        registry: BaseRegistry,
        task: MaterializationTask,
        **kwargs,
    ) -> MaterializationJob:
        ...

    def get_historical_features(self, task: HistoricalRetrievalTask) -> RetrievalJob:
        ...
  1. Create a FeatureBuilder
from feast.infra.compute_engines.feature_builder import FeatureBuilder


class CustomFeatureBuilder(FeatureBuilder):
    def build_source_node(self): ...
    def build_aggregation_node(self, input_node): ...
    def build_join_node(self, input_node): ...
    def build_filter_node(self, input_node):
    def build_dedup_node(self, input_node):
    def build_transformation_node(self, input_node): ...
    def build_output_nodes(self, input_node): ...
    def build_validation_node(self, input_node): ...
  1. Define DAGNode subclasses

    • ReadNode, AggregationNode, JoinNode, WriteNode, etc.
    • Each DAGNode.execute(context) -> DAGValue
  2. Return an ExecutionPlan

    • ExecutionPlan stores DAG nodes in topological order
    • Automatically handles intermediate value caching

🚧 Roadmap

  • Modular, backend-agnostic DAG execution framework
  • Spark engine with native support for materialization + PIT joins
  • PyArrow + Pandas engine for local compute
  • Native multi-feature-view DAG optimization
  • DAG validation, metrics, and debug output
  • Scalable distributed backend via Ray or Polars