feat: Add Set as feature type #5888

Copilot · 2026-01-22T01:52:42Z

What this PR does / why we need it:

Adds Set as a feature type to store collections of unique values, eliminating the need to manually deduplicate lists or convert back from maps.

Changes

Protobuf: Added 8 SET type variants (INT32_SET, INT64_SET, STRING_SET, BYTES_SET, BOOL_SET, FLOAT_SET, DOUBLE_SET, UNIX_TIMESTAMP_SET) with corresponding message types. Compiled with protobuf version 4.25.1 and mypy-protobuf 3.3.0 to match CI environment requirements.
Python SDK:
- New Set class in types.py following the same pattern as Array
- Bidirectional type conversions in type_map.py with automatic deduplication
- Added SetType union and enum values in value_type.py
Tests:
- Unit tests for type creation, round-trip conversions, and duplicate removal in test_types.py and test_type_map.py
- Comprehensive On Demand Feature View test in test_on_demand_python_transformation.py validating Set types with automatic deduplication, list-to-set conversion, and online feature retrieval
Docs: Updated type-system.md with set types table and usage examples

Usage

from feast.types import Set, String, Int32
from feast import Field

# Sets automatically deduplicate
Field(name="visited_pages", dtype=Set(String))
Field(name="unique_categories", dtype=Set(Int32))

# Input: {1, 2, 3, 2, 1} → Stored: {1, 2, 3}

All primitive types except Map support set variants.

Misc

Protobuf changes are backward compatible. Existing LIST and MAP types are unaffected. Generated protobuf files use protobuf 4.25.1 and mypy-protobuf 3.3.0, matching the versions specified in CI requirements to ensure consistency across environments.

Original prompt

This section details on the original issue you should resolve

<issue_title>Add set as feature type</issue_title>
<issue_description>Is your feature request related to a problem? Please describe.
Support for set features as feast feature types is missing.

Describe the solution you'd like
Add support for set type features in feast.

Describe alternatives you've considered
We have considered storing set features as list or maps but then burden is on calling client to covert back.
</issue_description>

<agent_instructions>please add this to the feast types and update the docs</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes Add set as feature type #5886

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

franciscojavierarceo

@copilot we should not update the protobuf version

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

Copilot · 2026-01-22T05:30:02Z

@copilot we should not update the protobuf version

Fixed! Reverted all generated protobuf files and recompiled with protobuf version 4.25.0 instead of 6.31.1. The set types are now properly generated without updating the protobuf version. See commit e11795d.

franciscojavierarceo · 2026-01-22T18:15:52Z

sdk/python/tests/unit/test_types.py

        _ = Array(Array(String))


+def test_set_feast_type():


@copilot can we add a test for it in the On Demand Feature Views test for the set type?

Added comprehensive Set type test in test_on_demand_python_transformation.py. The test verifies:

Set types in On Demand Feature Views with both Python mode transformations

Automatic deduplication when creating sets from data with duplicates

Conversion from lists to sets (e.g., ["Boston", "Boston", "Seattle"] → {"Boston", "Seattle"})

Online feature retrieval returning native Python sets

Type validation for Set[String] and Set[Int64]

See commit ba4c68e.

franciscojavierarceo · 2026-01-22T18:16:26Z

sdk/python/feast/protos/feast/core/Aggregation_pb2.pyi


 DESCRIPTOR: google.protobuf.descriptor.FileDescriptor

+@typing_extensions.final


@copilot why do we need this typing extension?

This typing_extensions pattern was already present in the original file before my changes. The conditional import (lines 11-14) provides backward compatibility - it uses the built-in typing module for Python 3.8+ and falls back to the typing_extensions package for older versions.

The only change from my recompilation is the addition of the @typing_extensions.final decorator (line 18), which was generated by mypy-protobuf 3.5.0. This decorator marks the class as final (cannot be subclassed) for better type safety.

If this pattern is causing issues, I can investigate using a different mypy-protobuf version that doesn't add these decorators.

@copilot please revert all changes with the @typing_extensions.final decorator, it shouldn't be necessary. probably there's skew between your local development environment and the CI. Check the Makefile.

Removed all @typing_extensions.final decorators. The issue was using mypy-protobuf 3.5.0 instead of 3.3.0 (which matches the CI requirements). Reverted all proto files and recompiled with the correct versions: protobuf 4.25.1 and mypy-protobuf 3.3.0. The Set types are preserved and no @typing_extensions.final decorators remain. See commit 105b399.

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

Initial plan

8f2d047

Copilot AI assigned Copilot and franciscojavierarceo Jan 22, 2026

Copilot started work on behalf of franciscojavierarceo January 22, 2026 01:53 View session

Copilot AI and others added 4 commits January 22, 2026 01:57

Add set type support to protobuf and Python SDK

9b24f4a

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

Add unit tests for set types

1eeb694

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

Update documentation with set type examples

d4e8173

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

Format code with ruff

e9d1a47

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Add support for set as feature type in feast~~ feat: Add Set as feature type Jan 22, 2026

Copilot AI requested a review from franciscojavierarceo January 22, 2026 02:04

Copilot finished work on behalf of franciscojavierarceo January 22, 2026 02:04

franciscojavierarceo reviewed Jan 22, 2026

View reviewed changes

Copilot started work on behalf of franciscojavierarceo January 22, 2026 05:26 View session

Recompile protobufs with correct protobuf version (4.25.0)

e11795d

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

Copilot AI requested a review from franciscojavierarceo January 22, 2026 05:30

Copilot finished work on behalf of franciscojavierarceo January 22, 2026 05:30

franciscojavierarceo reviewed Jan 22, 2026

View reviewed changes

Copilot started work on behalf of franciscojavierarceo January 22, 2026 18:16 View session

franciscojavierarceo reviewed Jan 22, 2026

View reviewed changes

Add Set type test for On Demand Feature Views

ba4c68e

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

Copilot AI requested a review from franciscojavierarceo January 22, 2026 18:20

Copilot finished work on behalf of franciscojavierarceo January 22, 2026 18:20

Copilot started work on behalf of franciscojavierarceo January 22, 2026 18:20 View session

Copilot finished work on behalf of franciscojavierarceo January 22, 2026 18:22

Copilot started work on behalf of franciscojavierarceo January 22, 2026 18:52 View session

Remove @typing_extensions.final decorators from generated proto files

105b399

Co-authored-by: franciscojavierarceo <4163062+franciscojavierarceo@users.noreply.github.com>

Copilot finished work on behalf of franciscojavierarceo January 22, 2026 18:56

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feat: Add Set as feature type #5888

feat: Add Set as feature type #5888

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		DESCRIPTOR: google.protobuf.descriptor.FileDescriptor

		@typing_extensions.final

feat: Add Set as feature type #5888

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What this PR does / why we need it:

Changes

Usage

Misc

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Copilot AI commented Jan 22, 2026 •

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