feat(firestore): support array functions by Linchin · Pull Request #16128 · googleapis/google-cloud-python

Linchin · 2026-03-18T23:05:43Z

Supports the following:

array_first
array_last
array_first_n
array_last_n
array_maximum
array_maximum_n
array_minimum
array_minimum_n
array_slice
array_index_of
array_index_of_all
array_transform (need to check for ref impl when it's ready - docstring, and sep methods or not)
array_filter (need to check for ref impl when it's ready - docstring, and sep methods or not)

gemini-code-assist · 2026-03-18T23:05:57Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the Firestore client library by integrating new array manipulation functions directly into pipeline expressions. This provides developers with more powerful and convenient ways to query and transform data within array fields, improving data processing capabilities without requiring client-side array handling.

Highlights

New Array Functions: Introduced array_first, array_last, array_first_n, and array_last_n to the Firestore pipeline expressions, allowing users to extract specific elements or sub-arrays from array fields.

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gemini-code-assist

Code Review

This pull request adds support for array_first, array_last, array_first_n, and array_last_n functions in Firestore pipelines. The implementation and system tests look good. However, I found issues in the unit tests for array_first_n and array_last_n where the parameter order is asserted incorrectly, leading to internally inconsistent tests. I've provided suggestions to fix these tests.

packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py

… tests.

…nit and system tests.

… array elements with optional index.

Linchin · 2026-03-21T01:04:10Z

/gemini review

gemini-code-assist

Code Review

This pull request adds support for a number of new array functions in Firestore pipelines. The implementation looks mostly good, but there are a few areas for improvement.

There are some inconsistencies in the naming of the generated functions (e.g., maximum vs array_maximum) which should be standardized. The e2e tests for these functions are also missing assert_proto blocks to verify the generated output.

Additionally, there are some minor issues with docstrings and redundant code that can be cleaned up. The signature for array_transform is also a bit confusing and could be made clearer.

Overall, a solid addition with a few refinements needed.

gemini-code-assist · 2026-03-21T01:06:56Z

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

+    def array_maximum(self) -> "Expression":
+        """Creates an expression that returns the maximum element of an array.
+
+        Example:
+            >>> # Select the maximum element of array 'scores'
+            >>> Field.of("scores").array_maximum()
+
+        Returns:
+            A new `Expression` representing the maximum element of the array.
+        """
+        return FunctionExpression("maximum", [self])


The function name used for array_maximum is "maximum". This is inconsistent with other new array functions like array_first which uses "array_first". For consistency, this should probably be "array_maximum".

This same issue applies to:

array_minimum (uses "minimum")

array_maximum_n (uses "maximum_n")

array_minimum_n (uses "minimum_n")

Please update them all to use the array_ prefix for consistency and to prevent potential backend errors.

return FunctionExpression("array_maximum", [self])

gemini-code-assist · 2026-03-21T01:06:57Z

packages/google-cloud-firestore/tests/system/pipeline_e2e/array.yaml

+                    name: array_last_n
+          name: select
+
+  - description: testArrayMaximum


This test, along with testArrayMinimum, testArrayMaximumN, testArrayMinimumN, testArraySlice1Arg, and testArraySlice2Args, is missing an assert_proto block. These assertions are crucial for verifying that the client is generating the correct protocol buffer messages for the backend. Please add them to ensure the implementation is correct. For example, this is needed to confirm whether the function name should be maximum or array_maximum.

gemini-code-assist · 2026-03-21T01:06:57Z

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

+    def array_slice(
+        self, offset: int | "Expression", length: int | "Expression" | None = None
+    ) -> "Expression":
+        """Ccreates an expression that returns a slice of an array starting from the specified


There is a typo in the docstring. "Ccreates" should be "Creates".

"""Creates an expression that returns a slice of an array starting from the specified

gemini-code-assist · 2026-03-21T01:06:57Z

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

+    def array_transform(
+        self, element_alias: str, body: "Expression", index_alias: str | None = None
+    ) -> "Expression":


The method signature for array_transform is (self, element_alias: str, body: "Expression", index_alias: str | None = None). However, the implementation and the expected backend protocol place the body argument last in the argument list sent to the backend. This discrepancy can be confusing and lead to incorrect usage.

To improve clarity and prevent misuse, consider making index_alias a keyword-only argument. This enforces that it's passed by name and makes the signature less ambiguous.

def array_transform( self, element_alias: str, body: "Expression", *, index_alias: str | None = None ) -> "Expression":

gemini-code-assist · 2026-03-21T01:06:57Z

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

+        if index_alias is not None:
+            args.append(self._cast_to_expr_or_convert_to_constant(index_alias))
+
+        args.append(self._cast_to_expr_or_convert_to_constant(body))


The body parameter is already typed as Expression. Calling _cast_to_expr_or_convert_to_constant on it is redundant, as unit tests suggest this function is a no-op for Expression instances. You can append body directly to the args list for clarity.

This also applies to array_filter on line 1733.

args.append(body)

gemini-code-assist · 2026-03-21T01:06:57Z

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

+        """
+        Takes an array, evaluates a boolean expression on each element, and returns a new
+        array containing only the elements for which the expression evaluates to True.
+
+        Args:
+           element_alias: Element variable name.
+           body: Boolean expression applied to each element.
+
+        Returns:
+            Expression: The created FunctionExpression AST node.
+        """


The docstring for array_filter is inconsistent with the other new functions in this PR.

It's missing an Example: section.

The Returns: description is not as user-friendly as the others.

Please update it for consistency. For example:

""" Takes an array and returns a new array containing only the elements for which the given boolean expression evaluates to True. Example: >>> # Filter for numbers greater than 5 >>> Field.of("numbers").array_filter("num", Field.of("num").greater_than(5)) Args: element_alias: Element variable name. body: Boolean expression applied to each element. Returns: A new `Expression` representing the filtered array. """

feat: support array_first, array_last, array_first_n, array_last_n

8a02c16

gemini-code-assist bot reviewed Mar 18, 2026

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packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py Outdated Show resolved Hide resolved

packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py Outdated Show resolved Hide resolved

Linchin added 9 commits March 18, 2026 23:13

fix unit test

bb7ddf5

support array_max, array_max_n, array_min, array_min_n

975c7e0

support array_slice

35eba8d

update docstring for array_slice

dad5c0d

feat: add array_index_of expression and corresponding unit and system…

4e1e847

… tests.

feat: add array_index_of_all expression for pipeline queries with u…

166f180

…nit and system tests.

feat: Add array_transform function to Expression for transforming…

755e643

… array elements with optional index.

implement array_filter

2bd5686

lint

496d8e2

gemini-code-assist bot reviewed Mar 21, 2026

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feat(firestore): support array functions#16128

feat(firestore): support array functions#16128
Linchin wants to merge 10 commits intogoogleapis:mainfrom
Linchin:fs-array

Linchin commented Mar 18, 2026 •

edited

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Linchin commented Mar 18, 2026 •

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