From 4e7cbf3a0027a9f884e3900f7ce24080bb34af5c Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 01:53:02 +0000
Subject: [PATCH 01/14] feat: support regex_find and regex_find_all

---
 .../firestore_v1/pipeline_expressions.py      | 42 ++++++++++
 .../tests/system/pipeline_e2e/string.yaml     | 83 +++++++++++++++++++
 .../unit/v1/test_pipeline_expressions.py      | 20 +++++
 3 files changed, 145 insertions(+)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index 325789f2358a..e7c6039a383c 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1307,6 +1307,48 @@ def map_merge(
             [self] + [self._cast_to_expr_or_convert_to_constant(m) for m in other_maps],
         )
 
+    @expose_as_static
+    def regex_find(self, pattern: str | Constant[str] | "Expression") -> "Expression":
+        """Creates an expression that returns the first substring of a string expression that
+        matches a specified regular expression.
+
+        This expression uses the RE2 regular expression syntax. See https://github.com/google/re2/wiki/Syntax.
+
+        Example:
+            >>> Field.of("email").regex_find("@[A-Za-z0-9.-]+")
+            >>> Field.of("email").regex_find(Field.of("pattern"))
+
+        Args:
+            pattern: The regular expression to search for.
+
+        Returns:
+            A new `Expression` representing the regular expression find function.
+        """
+        return FunctionExpression(
+            "regex_find", [self, self._cast_to_expr_or_convert_to_constant(pattern)]
+        )
+
+    @expose_as_static
+    def regex_find_all(self, pattern: str | Constant[str] | "Expression") -> "Expression":
+        """Creates an expression that evaluates to an array of all substrings in a string expression
+        that match a specified regular expression.
+
+        This expression uses the RE2 regular expression syntax. See https://github.com/google/re2/wiki/Syntax.
+
+        Example:
+            >>> Field.of("comment").regex_find_all("@[A-Za-z0-9_]+")
+            >>> Field.of("comment").regex_find_all(Field.of("pattern"))
+
+        Args:
+            pattern: The regular expression to search for.
+
+        Returns:
+            A new `Expression` representing the regular expression find function.
+        """
+        return FunctionExpression(
+            "regex_find_all", [self, self._cast_to_expr_or_convert_to_constant(pattern)]
+        )
+
     @expose_as_static
     def cosine_distance(self, other: Expression | list[float] | Vector) -> "Expression":
         """Calculates the cosine distance between two vectors.
diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index 20a97ba60663..b96ab506a10d 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -652,3 +652,86 @@ tests:
                     - stringValue: ", "
                     name: join
           name: select
+  - description: testRegexFind
+    pipeline:
+      - Collection: books
+      - Where:
+          - FunctionExpression.equal:
+              - Field: author
+              - Constant: "Douglas Adams"
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.regex_find:
+                - Field: title
+                - Constant: "Hitchhiker's"
+            - "found"
+    assert_results:
+      - found: "Hitchhiker's"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - functionValue:
+              args:
+              - fieldReferenceValue: author
+              - stringValue: "Douglas Adams"
+              name: equal
+          name: where
+        - args:
+          - mapValue:
+              fields:
+                found:
+                  functionValue:
+                    args:
+                    - fieldReferenceValue: title
+                    - stringValue: "Hitchhiker's"
+                    name: regex_find
+          name: select
+  - description: testRegexFindAll
+    pipeline:
+      - Collection: books
+      - Where:
+          - FunctionExpression.equal:
+              - Field: author
+              - Constant: "Douglas Adams"
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.regex_find_all:
+                - Field: title
+                - Constant: "(?i)[a-z]+"
+            - "found_all"
+    assert_results:
+      - found_all:
+        - "The"
+        - "Hitchhiker"
+        - "s"
+        - "Guide"
+        - "to"
+        - "the"
+        - "Galaxy"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - functionValue:
+              args:
+              - fieldReferenceValue: author
+              - stringValue: "Douglas Adams"
+              name: equal
+          name: where
+        - args:
+          - mapValue:
+              fields:
+                found_all:
+                  functionValue:
+                    args:
+                    - fieldReferenceValue: title
+                    - stringValue: "(?i)[a-z]+"
+                    name: regex_find_all
+          name: select
diff --git a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
index 80738799f975..b5a36505c6a1 100644
--- a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
+++ b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
@@ -1279,6 +1279,26 @@ def test_cosine_distance(self):
         infix_instance = arg1.cosine_distance(arg2)
         assert infix_instance == instance
 
+    def test_regex_find(self):
+        arg1 = self._make_arg("String")
+        arg2 = self._make_arg("pattern")
+        instance = Expression.regex_find(arg1, arg2)
+        assert instance.name == "regex_find"
+        assert instance.params == [arg1, arg2]
+        assert repr(instance) == "String.regex_find(pattern)"
+        infix_instance = arg1.regex_find(arg2)
+        assert infix_instance == instance
+
+    def test_regex_find_all(self):
+        arg1 = self._make_arg("String")
+        arg2 = self._make_arg("pattern")
+        instance = Expression.regex_find_all(arg1, arg2)
+        assert instance.name == "regex_find_all"
+        assert instance.params == [arg1, arg2]
+        assert repr(instance) == "String.regex_find_all(pattern)"
+        infix_instance = arg1.regex_find_all(arg2)
+        assert infix_instance == instance
+
     def test_dot_product(self):
         arg1 = self._make_arg("Vector1")
         arg2 = self._make_arg("Vector2")

From 2bc617048b45daa3a8c888576916fe9e24600ff7 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 02:15:58 +0000
Subject: [PATCH 02/14] support split

---
 .../firestore_v1/pipeline_expressions.py      | 18 ++++++++
 .../tests/system/pipeline_e2e/string.yaml     | 45 +++++++++++++++++++
 .../unit/v1/test_pipeline_expressions.py      | 10 +++++
 3 files changed, 73 insertions(+)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index e7c6039a383c..47a5ed311cb2 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1349,6 +1349,24 @@ def regex_find_all(self, pattern: str | Constant[str] | "Expression") -> "Expres
             "regex_find_all", [self, self._cast_to_expr_or_convert_to_constant(pattern)]
         )
 
+    @expose_as_static
+    def split(self, delimiter: str | "Expression") -> "Expression":
+        """Creates an expression that splits the value of a field on the provided delimiter.
+
+        Example:
+            >>> Field.of("date").split("date", "-")
+
+        Args:
+            field_name: Split the value in this field.
+            delimiter: The delimiter string to split on.
+
+        Returns:
+            A new `Expression` representing the split function.
+        """
+        return FunctionExpression(
+            "split", [self, self._cast_to_expr_or_convert_to_constant(delimiter)]
+        )
+
     @expose_as_static
     def cosine_distance(self, other: Expression | list[float] | Vector) -> "Expression":
         """Calculates the cosine distance between two vectors.
diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index b96ab506a10d..93bf65b15d00 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -735,3 +735,48 @@ tests:
                     - stringValue: "(?i)[a-z]+"
                     name: regex_find_all
           name: select
+
+  - description: testSplit
+    pipeline:
+      - Collection: books
+      - Where:
+          - FunctionExpression.equal:
+              - Field: author
+              - Constant: "Douglas Adams"
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.split:
+                - Field: title
+                - Constant: " "
+            - "title_words"
+    assert_results:
+      - title_words:
+        - "The"
+        - "Hitchhiker's"
+        - "Guide"
+        - "to"
+        - "the"
+        - "Galaxy"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - functionValue:
+              args:
+              - fieldReferenceValue: author
+              - stringValue: "Douglas Adams"
+              name: equal
+          name: where
+        - args:
+          - mapValue:
+              fields:
+                title_words:
+                  functionValue:
+                    args:
+                    - fieldReferenceValue: title
+                    - stringValue: " "
+                    name: split
+          name: select
diff --git a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
index b5a36505c6a1..3b8da3368bba 100644
--- a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
+++ b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
@@ -1299,6 +1299,16 @@ def test_regex_find_all(self):
         infix_instance = arg1.regex_find_all(arg2)
         assert infix_instance == instance
 
+    def test_split(self):
+        arg1 = self._make_arg("String")
+        arg2 = self._make_arg("-")
+        instance = Expression.split(arg1, arg2)
+        assert instance.name == "split"
+        assert instance.params == [arg1, arg2]
+        assert repr(instance) == "String.split(-)"
+        infix_instance = arg1.split(arg2)
+        assert infix_instance == instance
+
     def test_dot_product(self):
         arg1 = self._make_arg("Vector1")
         arg2 = self._make_arg("Vector2")

From 9a5c829a9efc38fcf5637cf693b7d7513670c6e2 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 02:32:40 +0000
Subject: [PATCH 03/14] support string_repeat()

---
 .../firestore_v1/pipeline_expressions.py      | 21 +++++++++
 .../tests/system/pipeline_e2e/string.yaml     | 44 +++++++++++++++++++
 .../unit/v1/test_pipeline_expressions.py      | 10 +++++
 3 files changed, 75 insertions(+)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index 47a5ed311cb2..b0c2f3406776 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1367,6 +1367,27 @@ def split(self, delimiter: str | "Expression") -> "Expression":
             "split", [self, self._cast_to_expr_or_convert_to_constant(delimiter)]
         )
 
+    @expose_as_static
+    def string_repeat(self, repetitions: int | "Expression") -> "Expression":
+        """Creates an expression that repeats a string or byte array a specified number
+        of times.
+
+        Example:
+            >>> # Called on an existing field expression:
+            >>> Field.of("name").string_repeat(3)
+            >>> # Called statically using the field name:
+            >>> Expression.string_repeat("name", 3)
+
+        Args:
+            repetitions: The number of times to repeat the string or byte array.
+
+        Returns:
+            A new `Expression` representing the repeated string or byte array.
+        """
+        return FunctionExpression(
+            "string_repeat", [self, self._cast_to_expr_or_convert_to_constant(repetitions)]
+        )
+
     @expose_as_static
     def cosine_distance(self, other: Expression | list[float] | Vector) -> "Expression":
         """Calculates the cosine distance between two vectors.
diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index 93bf65b15d00..5ca92cc0de03 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -780,3 +780,47 @@ tests:
                     - stringValue: " "
                     name: split
           name: select
+
+  - description: testStringRepeat
+    pipeline:
+      - Collection: books
+      - Where:
+          - FunctionExpression.equal:
+              - Field: author
+              - Constant: "Douglas Adams"
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.string_repeat:
+                - FunctionExpression.to_upper:
+                    - Field: author
+                - Constant: 2
+            - "repeated"
+    assert_results:
+      - repeated: "DOUGLAS ADAMSDOUGLAS ADAMS"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - functionValue:
+              args:
+              - fieldReferenceValue: author
+              - stringValue: "Douglas Adams"
+              name: equal
+          name: where
+        - args:
+          - mapValue:
+              fields:
+                repeated:
+                  functionValue:
+                    args:
+                    - functionValue:
+                        args:
+                        - fieldReferenceValue: author
+                        name: to_upper
+                    - integerValue: "2"
+                    name: string_repeat
+          name: select
+
diff --git a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
index 3b8da3368bba..7df15dfbd1a1 100644
--- a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
+++ b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
@@ -1309,6 +1309,16 @@ def test_split(self):
         infix_instance = arg1.split(arg2)
         assert infix_instance == instance
 
+    def test_string_repeat(self):
+        arg1 = self._make_arg("String")
+        arg2 = self._make_arg("3")
+        instance = Expression.string_repeat(arg1, arg2)
+        assert instance.name == "string_repeat"
+        assert instance.params == [arg1, arg2]
+        assert repr(instance) == "String.string_repeat(3)"
+        infix_instance = arg1.string_repeat(arg2)
+        assert infix_instance == instance
+
     def test_dot_product(self):
         arg1 = self._make_arg("Vector1")
         arg2 = self._make_arg("Vector2")

From c5b259d8685a99cb41509d2fb9c18c1af5d2cea1 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 02:34:00 +0000
Subject: [PATCH 04/14] type annotation

---
 .../google/cloud/firestore_v1/pipeline_expressions.py     | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index b0c2f3406776..0f4f591cf4f9 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1308,7 +1308,7 @@ def map_merge(
         )
 
     @expose_as_static
-    def regex_find(self, pattern: str | Constant[str] | "Expression") -> "Expression":
+    def regex_find(self, pattern: str | Constant[str] | Expression) -> "Expression":
         """Creates an expression that returns the first substring of a string expression that
         matches a specified regular expression.
 
@@ -1329,7 +1329,7 @@ def regex_find(self, pattern: str | Constant[str] | "Expression") -> "Expression
         )
 
     @expose_as_static
-    def regex_find_all(self, pattern: str | Constant[str] | "Expression") -> "Expression":
+    def regex_find_all(self, pattern: str | Constant[str] | Expression) -> "Expression":
         """Creates an expression that evaluates to an array of all substrings in a string expression
         that match a specified regular expression.
 
@@ -1350,7 +1350,7 @@ def regex_find_all(self, pattern: str | Constant[str] | "Expression") -> "Expres
         )
 
     @expose_as_static
-    def split(self, delimiter: str | "Expression") -> "Expression":
+    def split(self, delimiter: str | Constant[str] | Expression) -> "Expression":
         """Creates an expression that splits the value of a field on the provided delimiter.
 
         Example:
@@ -1368,7 +1368,7 @@ def split(self, delimiter: str | "Expression") -> "Expression":
         )
 
     @expose_as_static
-    def string_repeat(self, repetitions: int | "Expression") -> "Expression":
+    def string_repeat(self, repetitions: int | Expression) -> "Expression":
         """Creates an expression that repeats a string or byte array a specified number
         of times.
 

From 39de405f54bcb909a866dbce979d0008cef19384 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 02:43:43 +0000
Subject: [PATCH 05/14] support string_replace_all()

---
 .../firestore_v1/pipeline_expressions.py      | 29 +++++++++++++
 .../tests/system/pipeline_e2e/string.yaml     | 41 +++++++++++++++++++
 .../unit/v1/test_pipeline_expressions.py      | 11 +++++
 3 files changed, 81 insertions(+)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index 0f4f591cf4f9..79947ed7bbae 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1388,6 +1388,35 @@ def string_repeat(self, repetitions: int | Expression) -> "Expression":
             "string_repeat", [self, self._cast_to_expr_or_convert_to_constant(repetitions)]
         )
 
+    @expose_as_static
+    def string_replace_all(
+        self,
+        find: str | bytes | Constant | Expression,
+        replacement: str | bytes | Constant | Expression,
+    ) -> "Expression":
+        """Creates an expression that replaces all occurrences of a substring or byte
+        sequence with a replacement.
+
+        Example:
+            >>> # Called on an existing field expression:
+            >>> Field.of("text").string_replace_all("foo", "bar")
+
+        Args:
+            find: The substring or byte sequence to search for.
+            replacement: The replacement string or byte sequence.
+
+        Returns:
+            A new `Expression` representing the string or byte array with replacements.
+        """
+        return FunctionExpression(
+            "string_replace_all",
+            [
+                self,
+                self._cast_to_expr_or_convert_to_constant(find),
+                self._cast_to_expr_or_convert_to_constant(replacement),
+            ],
+        )
+
     @expose_as_static
     def cosine_distance(self, other: Expression | list[float] | Vector) -> "Expression":
         """Calculates the cosine distance between two vectors.
diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index 5ca92cc0de03..f0c9c7ba67a8 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -824,3 +824,44 @@ tests:
                     name: string_repeat
           name: select
 
+  - description: testStringReplaceAll
+    pipeline:
+      - Collection: books
+      - Where:
+          - FunctionExpression.equal:
+              - Field: author
+              - Constant: "Douglas Adams"
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.string_replace_all:
+                - Field: author
+                - Constant: "as"
+                - Constant: "AS"
+            - "replaced"
+    assert_results:
+      - replaced: "DouglAS Adams"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - functionValue:
+              args:
+              - fieldReferenceValue: author
+              - stringValue: "Douglas Adams"
+              name: equal
+          name: where
+        - args:
+          - mapValue:
+              fields:
+                replaced:
+                  functionValue:
+                    args:
+                    - fieldReferenceValue: author
+                    - stringValue: "as"
+                    - stringValue: "AS"
+                    name: string_replace_all
+          name: select
+
diff --git a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
index 7df15dfbd1a1..de5f4a0e8a5d 100644
--- a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
+++ b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
@@ -1319,6 +1319,17 @@ def test_string_repeat(self):
         infix_instance = arg1.string_repeat(arg2)
         assert infix_instance == instance
 
+    def test_string_replace_all(self):
+        arg1 = self._make_arg("String")
+        arg2 = self._make_arg("find")
+        arg3 = self._make_arg("replacement")
+        instance = Expression.string_replace_all(arg1, arg2, arg3)
+        assert instance.name == "string_replace_all"
+        assert instance.params == [arg1, arg2, arg3]
+        assert repr(instance) == "String.string_replace_all(find, replacement)"
+        infix_instance = arg1.string_replace_all(arg2, arg3)
+        assert infix_instance == instance
+
     def test_dot_product(self):
         arg1 = self._make_arg("Vector1")
         arg2 = self._make_arg("Vector2")

From 34acf715fa1fdf9d0dd39b092077f8e196967a0e Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 02:48:25 +0000
Subject: [PATCH 06/14] improve system test

---
 .../tests/system/pipeline_e2e/string.yaml     | 30 ++++++++++++-------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index f0c9c7ba67a8..5976ba1b442e 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -829,17 +829,20 @@ tests:
       - Collection: books
       - Where:
           - FunctionExpression.equal:
-              - Field: author
-              - Constant: "Douglas Adams"
+              - Field: title
+              - Constant: "The Hitchhiker's Guide to the Galaxy"
       - Select:
         - AliasedExpression:
             - FunctionExpression.string_replace_all:
-                - Field: author
-                - Constant: "as"
-                - Constant: "AS"
+                - FunctionExpression.concat:
+                    - Field: author
+                    - Constant: ": "
+                    - Field: title
+                - Constant: "la"
+                - Constant: "LA"
             - "replaced"
     assert_results:
-      - replaced: "DouglAS Adams"
+      - replaced: "DougLAs Adams: The Hitchhiker's Guide to the GaLAxy"
     assert_proto:
       pipeline:
         stages:
@@ -849,8 +852,8 @@ tests:
         - args:
           - functionValue:
               args:
-              - fieldReferenceValue: author
-              - stringValue: "Douglas Adams"
+              - fieldReferenceValue: title
+              - stringValue: "The Hitchhiker's Guide to the Galaxy"
               name: equal
           name: where
         - args:
@@ -859,9 +862,14 @@ tests:
                 replaced:
                   functionValue:
                     args:
-                    - fieldReferenceValue: author
-                    - stringValue: "as"
-                    - stringValue: "AS"
+                    - functionValue:
+                        args:
+                        - fieldReferenceValue: author
+                        - stringValue: ": "
+                        - fieldReferenceValue: title
+                        name: concat
+                    - stringValue: "la"
+                    - stringValue: "LA"
                     name: string_replace_all
           name: select
 

From 22fd6adf8437e66231660d2c0217a16f3b6bd700 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 02:52:48 +0000
Subject: [PATCH 07/14] support string_replace_one()

---
 .../firestore_v1/pipeline_expressions.py      | 29 +++++++++++
 .../tests/system/pipeline_e2e/string.yaml     | 49 +++++++++++++++++++
 .../unit/v1/test_pipeline_expressions.py      | 11 +++++
 3 files changed, 89 insertions(+)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index 79947ed7bbae..07710b6f2411 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1417,6 +1417,35 @@ def string_replace_all(
             ],
         )
 
+    @expose_as_static
+    def string_replace_one(
+        self,
+        find: str | bytes | Constant | Expression,
+        replacement: str | bytes | Constant | Expression,
+    ) -> "Expression":
+        """Creates an expression that replaces the first occurrence of a substring or byte
+        sequence with a replacement.
+
+        Example:
+            >>> # Called on an existing field expression:
+            >>> Field.of("text").string_replace_one("foo", "bar")
+
+        Args:
+            find: The substring or byte sequence to search for.
+            replacement: The replacement string or byte sequence.
+
+        Returns:
+            A new `Expression` representing the string or byte array with the replacement.
+        """
+        return FunctionExpression(
+            "string_replace_one",
+            [
+                self,
+                self._cast_to_expr_or_convert_to_constant(find),
+                self._cast_to_expr_or_convert_to_constant(replacement),
+            ],
+        )
+
     @expose_as_static
     def cosine_distance(self, other: Expression | list[float] | Vector) -> "Expression":
         """Calculates the cosine distance between two vectors.
diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index 5976ba1b442e..60dbfb7e98fc 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -873,3 +873,52 @@ tests:
                     name: string_replace_all
           name: select
 
+  - description: testStringReplaceOne
+    pipeline:
+      - Collection: books
+      - Where:
+          - FunctionExpression.equal:
+              - Field: title
+              - Constant: "The Hitchhiker's Guide to the Galaxy"
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.string_replace_one:
+                - FunctionExpression.concat:
+                    - Field: author
+                    - Constant: ": "
+                    - Field: title
+                - Constant: "la"
+                - Constant: "LA"
+            - "replaced"
+    assert_results:
+      - replaced: "DougLAs Adams: The Hitchhiker's Guide to the Galaxy"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - functionValue:
+              args:
+              - fieldReferenceValue: title
+              - stringValue: "The Hitchhiker's Guide to the Galaxy"
+              name: equal
+          name: where
+        - args:
+          - mapValue:
+              fields:
+                replaced:
+                  functionValue:
+                    args:
+                    - functionValue:
+                        args:
+                        - fieldReferenceValue: author
+                        - stringValue: ": "
+                        - fieldReferenceValue: title
+                        name: concat
+                    - stringValue: "la"
+                    - stringValue: "LA"
+                    name: string_replace_one
+          name: select
+
diff --git a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
index de5f4a0e8a5d..0d33b3129ceb 100644
--- a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
+++ b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
@@ -1330,6 +1330,17 @@ def test_string_replace_all(self):
         infix_instance = arg1.string_replace_all(arg2, arg3)
         assert infix_instance == instance
 
+    def test_string_replace_one(self):
+        arg1 = self._make_arg("String")
+        arg2 = self._make_arg("find")
+        arg3 = self._make_arg("replacement")
+        instance = Expression.string_replace_one(arg1, arg2, arg3)
+        assert instance.name == "string_replace_one"
+        assert instance.params == [arg1, arg2, arg3]
+        assert repr(instance) == "String.string_replace_one(find, replacement)"
+        infix_instance = arg1.string_replace_one(arg2, arg3)
+        assert infix_instance == instance
+
     def test_dot_product(self):
         arg1 = self._make_arg("Vector1")
         arg2 = self._make_arg("Vector2")

From e810622e492a71adcb2569f333786a8edfc40dca Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 03:00:19 +0000
Subject: [PATCH 08/14] support string_index_of()

---
 .../firestore_v1/pipeline_expressions.py      | 26 +++++++++++++
 .../tests/system/pipeline_e2e/string.yaml     | 39 +++++++++++++++++++
 .../unit/v1/test_pipeline_expressions.py      | 10 +++++
 3 files changed, 75 insertions(+)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index 07710b6f2411..fd8c7e6dc4e0 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1446,6 +1446,32 @@ def string_replace_one(
             ],
         )
 
+    @expose_as_static
+    def string_index_of(
+        self,
+        search: str | bytes | Constant | Expression,
+    ) -> "Expression":
+        """Creates an expression that finds the index of the first occurrence of a substring or
+        byte sequence.
+
+        Example:
+            >>> # Called on an existing field expression:
+            >>> Field.of("text").string_index_of("foo")
+
+        Args:
+            search: The substring or byte sequence to search for.
+
+        Returns:
+            A new `Expression` representing the index of the first occurrence.
+        """
+        return FunctionExpression(
+            "string_index_of",
+            [
+                self,
+                self._cast_to_expr_or_convert_to_constant(search),
+            ],
+        )
+
     @expose_as_static
     def cosine_distance(self, other: Expression | list[float] | Vector) -> "Expression":
         """Calculates the cosine distance between two vectors.
diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index 60dbfb7e98fc..f585d37439d7 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -922,3 +922,42 @@ tests:
                     name: string_replace_one
           name: select
 
+  - description: testStringIndexOf
+    pipeline:
+      - Collection: books
+      - Where:
+          - FunctionExpression.equal:
+              - Field: title
+              - Constant: "The Hitchhiker's Guide to the Galaxy"
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.string_index_of:
+                - Field: title
+                - Constant: "Hitchhiker"
+            - "index"
+    assert_results:
+      - index: 4
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - functionValue:
+              args:
+              - fieldReferenceValue: title
+              - stringValue: "The Hitchhiker's Guide to the Galaxy"
+              name: equal
+          name: where
+        - args:
+          - mapValue:
+              fields:
+                index:
+                  functionValue:
+                    args:
+                    - fieldReferenceValue: title
+                    - stringValue: "Hitchhiker"
+                    name: string_index_of
+          name: select
+
diff --git a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
index 0d33b3129ceb..0219127defb5 100644
--- a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
+++ b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
@@ -1341,6 +1341,16 @@ def test_string_replace_one(self):
         infix_instance = arg1.string_replace_one(arg2, arg3)
         assert infix_instance == instance
 
+    def test_string_index_of(self):
+        arg1 = self._make_arg("String")
+        arg2 = self._make_arg("search")
+        instance = Expression.string_index_of(arg1, arg2)
+        assert instance.name == "string_index_of"
+        assert instance.params == [arg1, arg2]
+        assert repr(instance) == "String.string_index_of(search)"
+        infix_instance = arg1.string_index_of(arg2)
+        assert infix_instance == instance
+
     def test_dot_product(self):
         arg1 = self._make_arg("Vector1")
         arg2 = self._make_arg("Vector2")

From 6870cd1907b319094dfa36427402761035f11131 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 03:01:57 +0000
Subject: [PATCH 09/14] improve type hint

---
 .../google/cloud/firestore_v1/pipeline_expressions.py         | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index fd8c7e6dc4e0..85d6fc56c90a 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1391,8 +1391,8 @@ def string_repeat(self, repetitions: int | Expression) -> "Expression":
     @expose_as_static
     def string_replace_all(
         self,
-        find: str | bytes | Constant | Expression,
-        replacement: str | bytes | Constant | Expression,
+        find: str | bytes | Constant[str] | Constant[bytes] | Expression,
+        replacement: str | bytes | Constant[str] | Constant[bytes] | Expression,
     ) -> "Expression":
         """Creates an expression that replaces all occurrences of a substring or byte
         sequence with a replacement.

From b91062ab72a49338bc465951d7749aa1d93e2888 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 03:11:58 +0000
Subject: [PATCH 10/14] type hints

---
 .../google/cloud/firestore_v1/pipeline_expressions.py       | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index 85d6fc56c90a..593fe0a68ad2 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1420,8 +1420,8 @@ def string_replace_all(
     @expose_as_static
     def string_replace_one(
         self,
-        find: str | bytes | Constant | Expression,
-        replacement: str | bytes | Constant | Expression,
+        find: str | bytes | Constant[str] | Constant[bytes] | Expression,
+        replacement: str | bytes | Constant[str] | Constant[bytes] | Expression,
     ) -> "Expression":
         """Creates an expression that replaces the first occurrence of a substring or byte
         sequence with a replacement.
@@ -1449,7 +1449,7 @@ def string_replace_one(
     @expose_as_static
     def string_index_of(
         self,
-        search: str | bytes | Constant | Expression,
+        search: str | bytes | Constant[str] | Constant[bytes] | Expression,
     ) -> "Expression":
         """Creates an expression that finds the index of the first occurrence of a substring or
         byte sequence.

From 2ed994e105830b4dcc94fbead2b8f000732dcce5 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 03:19:39 +0000
Subject: [PATCH 11/14] add system tests for bytes

---
 .../tests/system/pipeline_e2e/string.yaml     | 99 +++++++++++++++++++
 1 file changed, 99 insertions(+)

diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index f585d37439d7..05313348ce61 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -873,6 +873,40 @@ tests:
                     name: string_replace_all
           name: select
 
+  - description: testStringReplaceAllWithBytes
+    pipeline:
+      - Collection: books
+      - Limit: 1
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.string_replace_all:
+                - Constant: !!binary Zm9vYmF6Zm9v
+                - Constant: !!binary Zm9v
+                - Constant: !!binary YmFy
+            - "replacedBytes"
+    assert_results:
+      - replacedBytes: !!binary YmFyYmF6YmFy
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - integerValue: '1'
+          name: limit
+        - args:
+          - mapValue:
+              fields:
+                replacedBytes:
+                  functionValue:
+                    args:
+                    - bytesValue: Zm9vYmF6Zm9v
+                    - bytesValue: Zm9v
+                    - bytesValue: YmFy
+                    name: string_replace_all
+          name: select
+
   - description: testStringReplaceOne
     pipeline:
       - Collection: books
@@ -922,6 +956,40 @@ tests:
                     name: string_replace_one
           name: select
 
+  - description: testStringReplaceOneWithBytes
+    pipeline:
+      - Collection: books
+      - Limit: 1
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.string_replace_one:
+                - Constant: !!binary Zm9vYmF6Zm9v
+                - Constant: !!binary Zm9v
+                - Constant: !!binary YmFy
+            - "replacedBytes"
+    assert_results:
+      - replacedBytes: !!binary YmFyYmF6Zm9v
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - integerValue: '1'
+          name: limit
+        - args:
+          - mapValue:
+              fields:
+                replacedBytes:
+                  functionValue:
+                    args:
+                    - bytesValue: Zm9vYmF6Zm9v
+                    - bytesValue: Zm9v
+                    - bytesValue: YmFy
+                    name: string_replace_one
+          name: select
+
   - description: testStringIndexOf
     pipeline:
       - Collection: books
@@ -961,3 +1029,34 @@ tests:
                     name: string_index_of
           name: select
 
+  - description: testStringIndexOfWithBytes
+    pipeline:
+      - Collection: books
+      - Limit: 1
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.string_index_of:
+                - Constant: !!binary Zm9vYmF6
+                - Constant: !!binary YmF6
+            - "index"
+    assert_results:
+      - index: 3
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - integerValue: '1'
+          name: limit
+        - args:
+          - mapValue:
+              fields:
+                index:
+                  functionValue:
+                    args:
+                    - bytesValue: Zm9vYmF6
+                    - bytesValue: YmF6
+                    name: string_index_of
+          name: select

From c05adc58d39b20bcf3aa3d24f4753e8983fdae2e Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 03:37:22 +0000
Subject: [PATCH 12/14] support ltrim() and rtrim()

---
 .../firestore_v1/pipeline_expressions.py      |  52 +++++
 .../tests/system/pipeline_e2e/string.yaml     | 188 ++++++++++++++++++
 .../unit/v1/test_pipeline_expressions.py      |  40 ++++
 3 files changed, 280 insertions(+)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index 593fe0a68ad2..e28c2a30c1e5 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1472,6 +1472,58 @@ def string_index_of(
             ],
         )
 
+    @expose_as_static
+    def ltrim(
+        self,
+        chars: str | bytes | Constant[str] | Constant[bytes] | Expression | None = None,
+    ) -> "Expression":
+        """Creates an expression that trims leading whitespace or a specified sequence
+        of characters/bytes from a string or byte sequence.
+
+        Example:
+            >>> # Called on an existing field expression:
+            >>> Field.of("text").ltrim()
+            >>> Field.of("text").ltrim(" ")
+
+        Args:
+            chars: The substring or byte sequence to trim. If not provided,
+                whitespace will be trimmed.
+
+        Returns:
+            A new `Expression` representing the trimmed value.
+        """
+        args = [self]
+        if chars is not None:
+            args.append(self._cast_to_expr_or_convert_to_constant(chars))
+
+        return FunctionExpression("ltrim", args)
+
+    @expose_as_static
+    def rtrim(
+        self,
+        chars: str | bytes | Constant[str] | Constant[bytes] | Expression | None = None,
+    ) -> "Expression":
+        """Creates an expression that trims trailing whitespace or a specified sequence
+        of characters/bytes from a string or byte sequence.
+
+        Example:
+            >>> # Called on an existing field expression:
+            >>> Field.of("text").rtrim()
+            >>> Field.of("text").rtrim(" ")
+
+        Args:
+            chars: The substring or byte sequence to trim. If not provided,
+                whitespace will be trimmed.
+
+        Returns:
+            A new `Expression` representing the trimmed value.
+        """
+        args = [self]
+        if chars is not None:
+            args.append(self._cast_to_expr_or_convert_to_constant(chars))
+
+        return FunctionExpression("rtrim", args)
+
     @expose_as_static
     def cosine_distance(self, other: Expression | list[float] | Vector) -> "Expression":
         """Calculates the cosine distance between two vectors.
diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index 05313348ce61..acb55c58c413 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -1060,3 +1060,191 @@ tests:
                     - bytesValue: YmF6
                     name: string_index_of
           name: select
+
+  - description: testLtrim
+    pipeline:
+      - Collection: books
+      - Limit: 1
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.ltrim:
+                - Constant: "  foo"
+            - "trimmed"
+    assert_results:
+      - trimmed: "foo"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - integerValue: '1'
+          name: limit
+        - args:
+          - mapValue:
+              fields:
+                trimmed:
+                  functionValue:
+                    args:
+                    - stringValue: "  foo"
+                    name: ltrim
+          name: select
+
+  - description: testLtrimWithChars
+    pipeline:
+      - Collection: books
+      - Limit: 1
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.ltrim:
+                - Constant: "foobar"
+                - Constant: "fo"
+            - "trimmed"
+    assert_results:
+      - trimmed: "bar"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - integerValue: '1'
+          name: limit
+        - args:
+          - mapValue:
+              fields:
+                trimmed:
+                  functionValue:
+                    args:
+                    - stringValue: "foobar"
+                    - stringValue: "fo"
+                    name: ltrim
+          name: select
+
+  - description: testLtrimWithBytes
+    pipeline:
+      - Collection: books
+      - Limit: 1
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.ltrim:
+                - Constant: !!binary Zm9vYmFy
+                - Constant: !!binary Zm8=
+            - "trimmed"
+    assert_results:
+      - trimmed: !!binary YmFy
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - integerValue: '1'
+          name: limit
+        - args:
+          - mapValue:
+              fields:
+                trimmed:
+                  functionValue:
+                    args:
+                    - bytesValue: Zm9vYmFy
+                    - bytesValue: Zm8=
+                    name: ltrim
+          name: select
+
+  - description: testRtrim
+    pipeline:
+      - Collection: books
+      - Limit: 1
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.rtrim:
+                - Constant: "foo  "
+            - "trimmed"
+    assert_results:
+      - trimmed: "foo"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - integerValue: '1'
+          name: limit
+        - args:
+          - mapValue:
+              fields:
+                trimmed:
+                  functionValue:
+                    args:
+                    - stringValue: "foo  "
+                    name: rtrim
+          name: select
+
+  - description: testRtrimWithChars
+    pipeline:
+      - Collection: books
+      - Limit: 1
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.rtrim:
+                - Constant: "foobar"
+                - Constant: "ar"
+            - "trimmed"
+    assert_results:
+      - trimmed: "foob"
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - integerValue: '1'
+          name: limit
+        - args:
+          - mapValue:
+              fields:
+                trimmed:
+                  functionValue:
+                    args:
+                    - stringValue: "foobar"
+                    - stringValue: "ar"
+                    name: rtrim
+          name: select
+
+  - description: testRtrimWithBytes
+    pipeline:
+      - Collection: books
+      - Limit: 1
+      - Select:
+        - AliasedExpression:
+            - FunctionExpression.rtrim:
+                - Constant: !!binary Zm9vYmFy
+                - Constant: !!binary YXI=
+            - "trimmed"
+    assert_results:
+      - trimmed: !!binary Zm9vYg==
+    assert_proto:
+      pipeline:
+        stages:
+        - args:
+          - referenceValue: /books
+          name: collection
+        - args:
+          - integerValue: '1'
+          name: limit
+        - args:
+          - mapValue:
+              fields:
+                trimmed:
+                  functionValue:
+                    args:
+                    - bytesValue: Zm9vYmFy
+                    - bytesValue: YXI=
+                    name: rtrim
+          name: select
diff --git a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
index 0219127defb5..ca4ddd782a73 100644
--- a/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
+++ b/packages/google-cloud-firestore/tests/unit/v1/test_pipeline_expressions.py
@@ -1351,6 +1351,46 @@ def test_string_index_of(self):
         infix_instance = arg1.string_index_of(arg2)
         assert infix_instance == instance
 
+    def test_ltrim(self):
+        arg1 = self._make_arg("String")
+        arg2 = self._make_arg("chars")
+
+        # Without args
+        instance = Expression.ltrim(arg1)
+        assert instance.name == "ltrim"
+        assert instance.params == [arg1]
+        assert repr(instance) == "String.ltrim()"
+        infix_instance = arg1.ltrim()
+        assert infix_instance == instance
+
+        # With args
+        instance = Expression.ltrim(arg1, arg2)
+        assert instance.name == "ltrim"
+        assert instance.params == [arg1, arg2]
+        assert repr(instance) == "String.ltrim(chars)"
+        infix_instance = arg1.ltrim(arg2)
+        assert infix_instance == instance
+
+    def test_rtrim(self):
+        arg1 = self._make_arg("String")
+        arg2 = self._make_arg("chars")
+
+        # Without args
+        instance = Expression.rtrim(arg1)
+        assert instance.name == "rtrim"
+        assert instance.params == [arg1]
+        assert repr(instance) == "String.rtrim()"
+        infix_instance = arg1.rtrim()
+        assert infix_instance == instance
+
+        # With args
+        instance = Expression.rtrim(arg1, arg2)
+        assert instance.name == "rtrim"
+        assert instance.params == [arg1, arg2]
+        assert repr(instance) == "String.rtrim(chars)"
+        infix_instance = arg1.rtrim(arg2)
+        assert infix_instance == instance
+
     def test_dot_product(self):
         arg1 = self._make_arg("Vector1")
         arg2 = self._make_arg("Vector2")

From 4097985b17b5360656fb6c80f8ba93543791a765 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 03:47:28 +0000
Subject: [PATCH 13/14] lint

---
 .../google/cloud/firestore_v1/pipeline_expressions.py          | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
index e28c2a30c1e5..4e0a154c2b58 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_expressions.py
@@ -1385,7 +1385,8 @@ def string_repeat(self, repetitions: int | Expression) -> "Expression":
             A new `Expression` representing the repeated string or byte array.
         """
         return FunctionExpression(
-            "string_repeat", [self, self._cast_to_expr_or_convert_to_constant(repetitions)]
+            "string_repeat",
+            [self, self._cast_to_expr_or_convert_to_constant(repetitions)],
         )
 
     @expose_as_static

From 02f0c2cb381159e592dfa77c30f85ad576b210d7 Mon Sep 17 00:00:00 2001
From: Linchin <lingqing.gan@gmail.com>
Date: Tue, 24 Mar 2026 23:18:13 +0000
Subject: [PATCH 14/14] improve regex test case

---
 .../tests/system/pipeline_e2e/string.yaml                   | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
index acb55c58c413..097ccab859df 100644
--- a/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
+++ b/packages/google-cloud-firestore/tests/system/pipeline_e2e/string.yaml
@@ -663,10 +663,10 @@ tests:
         - AliasedExpression:
             - FunctionExpression.regex_find:
                 - Field: title
-                - Constant: "Hitchhiker's"
+                - Constant: '\b[A-Z][a-z]{4}\b'
             - "found"
     assert_results:
-      - found: "Hitchhiker's"
+      - found: "Guide"
     assert_proto:
       pipeline:
         stages:
@@ -687,7 +687,7 @@ tests:
                   functionValue:
                     args:
                     - fieldReferenceValue: title
-                    - stringValue: "Hitchhiker's"
+                    - stringValue: '\b[A-Z][a-z]{4}\b'
                     name: regex_find
           name: select
   - description: testRegexFindAll