feat(firestore): support let stage by Linchin · Pull Request #16030 · googleapis/google-cloud-python

Linchin · 2026-03-05T00:59:42Z

TODO:

verify docstring
add variable_field_reference

gemini-code-assist · 2026-03-05T01:00:01Z

Summary of Changes

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This pull request introduces the let pipeline stage to the Firestore client library, enabling users to define and compute variables within a pipeline. These variables can then be referenced in subsequent stages, significantly enhancing the flexibility and expressiveness of data processing pipelines by allowing intermediate calculations and named values.

Highlights

New 'let' Pipeline Stage: Introduced a new let pipeline stage that allows users to define and compute variables within a Firestore pipeline, enhancing data manipulation capabilities.
Core Implementation: Implemented the Let class in pipeline_stages.py to handle the internal logic and protobuf serialization for the new let stage.
Comprehensive Testing: Added both system-level (YAML) and unit tests to validate the functionality, correct argument handling, and protobuf conversion of the let pipeline stage.

Changelog

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py
- Added the let method to the _BasePipeline class, allowing users to define variables for subsequent pipeline stages.
packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_stages.py
- Implemented a new Let class, inheriting from Stage, to represent the 'let' pipeline stage internally.
- Added _pb_args method to the Let class for converting defined variables into the appropriate protobuf format.
packages/google-cloud-firestore/tests/system/pipeline_e2e/general.yaml
- Included a new system test case (testLetStage) to verify the functionality and correct proto generation of the let pipeline stage.
packages/google-cloud-firestore/tests/unit/v1/test_pipeline.py
- Updated the test_pipeline_methods function to correctly handle keyword arguments for the newly introduced let pipeline stage.
packages/google-cloud-firestore/tests/unit/v1/test_pipeline_stages.py
- Added comprehensive unit tests for the Let class, covering its constructor, string representation (__repr__), and protobuf conversion (_to_pb).

Activity

The author has noted two outstanding TODOs: verifying docstrings and adding variable_field_reference, indicating planned follow-up work for this feature.

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Code Review

This pull request introduces support for the let stage in Firestore pipelines, which is a great feature. The implementation looks solid, with new classes for the stage, methods on the pipeline builder, and thorough unit and system tests. I have a couple of suggestions: one to improve the clarity of the docstring for the new let method, and another to ensure deterministic behavior by sorting variables in the Let stage, following repository best practices.

gemini-code-assist · 2026-03-05T01:01:28Z

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py

+            ...     rating_plus_one=add(Field.of("rating"), 1),
+            ...     has_awards=Field.of("awards").exists()
+            ... )
+            >>> # Later stages can use Variable.of("rating_plus_one")


The docstring mentions Variable.of("rating_plus_one"), but the Variable class or a way to reference variables doesn't seem to be part of this pull request, as indicated by the TODO item add variable_field_reference. To avoid confusion and documenting a feature that is not yet available, it would be better to remove this line. The preceding sentences already explain that variables can be used in subsequent stages.

gemini-code-assist · 2026-03-05T01:01:28Z

packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_stages.py

+
+    def __init__(self, **variables: Expression):
+        super().__init__("let")
+        self.variables = variables


To ensure deterministic output for __repr__ and protobuf serialization, it's a good practice to sort the variables. This aligns with the general principle of producing predictable output, which is especially helpful for testing. You can sort the variables by key when they are assigned in the constructor.

Suggested change

self.variables = variables

self.variables = dict(sorted(variables.items()))

References

To ensure dictionary keys remain sorted without manual effort, programmatically sort the dictionary before returning it (e.g., using dict(sorted(metadata.items()))) instead of relying on manual ordering in the code.

Linchin · 2026-03-10T22:50:40Z

/gemini review

gemini-code-assist

Code Review

The pull request introduces support for the let stage in Firestore pipelines, allowing users to declare variables that can be referenced in subsequent stages. This includes the addition of a let method to the _BasePipeline class, a new Variable class for referencing these variables, and a Let stage class for processing the variable declarations. The changes are well-tested with both unit and system tests, ensuring correct functionality and protobuf serialization. However, there is a minor inconsistency in the docstring example for the let method regarding how Variable objects are instantiated.

gemini-code-assist · 2026-03-10T22:53:38Z

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py

+            ...     rating_plus_one=add(Field.of("rating"), 1),
+            ...     has_awards=Field.of("awards").exists()
+            ... )
+            >>> # Later stages can use Variable.of("rating_plus_one")


The example in the docstring suggests using Variable.of("rating_plus_one"), but the Variable class does not have an of class method. It should be instantiated directly as Variable("rating_plus_one").

Suggested change

>>> # Later stages can use Variable.of("rating_plus_one")

>>> # Later stages can use Variable("rating_plus_one")

wu-hui · 2026-03-11T19:04:12Z

packages/google-cloud-firestore/google/cloud/firestore_v1/base_pipeline.py

            stages.FindNearest(field, vector, distance_measure, options)
        )

+    def let(self, **variables: Expression) -> "_BasePipeline":


Drive-by comment, we are using define instead of let for our SDKs(mobile/web/java/node). There is active discussions happening right now on the naming. You probably need to rename it depending on how the discussion goes.

Thanks for the heads up! Will ping you

Linchin · 2026-03-11T20:52:08Z

Currently blocked by potential renaming per #16030 (comment)

feat(firestore): support let stage

031367f

gemini-code-assist bot reviewed Mar 5, 2026

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Merge branch 'main' into fs-let

7de72fb

Linchin marked this pull request as ready for review March 5, 2026 17:43

Linchin requested review from a team as code owners March 5, 2026 17:43

Linchin added 2 commits March 5, 2026 18:50

add Variable and fix system test

90e3734

docstring and lint

0844e23

Linchin assigned daniel-sanche Mar 10, 2026

gemini-code-assist bot reviewed Mar 10, 2026

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wu-hui reviewed Mar 11, 2026

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Linchin added the do not merge Indicates a pull request not ready for merge, due to either quality or timing. label Mar 11, 2026

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feat(firestore): support let stage#16030

feat(firestore): support let stage#16030
Linchin wants to merge 4 commits intogoogleapis:mainfrom
Linchin:fs-let

Linchin commented Mar 5, 2026 •

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	self.variables = variables
	self.variables = dict(sorted(variables.items()))

	>>> # Later stages can use Variable.of("rating_plus_one")
	>>> # Later stages can use Variable("rating_plus_one")

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Linchin commented Mar 5, 2026 •

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