SNOW-1438001: Add support for list values in Series.str.len (#2594)

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   Fixes SNOW-1438001

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3. Please describe how your code solves the related issue.

   Add support for list values in Series.str.len.

CHANGELOG.md

@@ -46,6 +46,7 @@
 - Added support for `pd.read_html` (Uses native pandas for processing).
 - Added support for `pd.read_xml` (Uses native pandas for processing).
 - Added support for aggregation functions `"size"` and `len` in `GroupBy.aggregate`, `DataFrame.aggregate`, and `Series.aggregate`.
+- Added support for list values in `Series.str.len`.
 
 #### Bug Fixes
 

docs/source/modin/supported/series_str_supported.rst

@@ -76,7 +76,8 @@ the method in the left column.
 +-----------------------------+---------------------------------+----------------------------------------------------+
 | ``join``                    | N                               |                                                    |
 +-----------------------------+---------------------------------+----------------------------------------------------+
-| ``len``                     | Y                               |                                                    |
+| ``len``                     | P                               | Only string and list data values are supported.    |
+|                             |                                 | All column values must be of the same type.        |
 +-----------------------------+---------------------------------+----------------------------------------------------+
 | ``ljust``                   | N                               |                                                    |
 +-----------------------------+---------------------------------+----------------------------------------------------+

src/snowflake/snowpark/modin/plugin/compiler/snowflake_query_compiler.py

@@ -85,6 +85,7 @@
 from snowflake.snowpark.functions import (
     abs as abs_,
     array_construct,
+    array_size,
     bround,
     builtin,
     cast,
@@ -16553,12 +16554,23 @@ def str_len(self, **kwargs: Any) -> "SnowflakeQueryCompiler":
         -------
         SnowflakeQueryCompiler representing result of the string operation.
         """
-        # TODO SNOW-1438001: Handle dict, list, and tuple values for Series.str.len().
-        return SnowflakeQueryCompiler(
-            self._modin_frame.apply_snowpark_function_to_columns(
-                lambda col: self._replace_non_str(col, length(col))
+        # TODO SNOW-1438001: Handle dict, and tuple values for Series.str.len().
+        col = self._modin_frame.data_column_snowflake_quoted_identifiers[0]
+        if isinstance(
+            self._modin_frame.quoted_identifier_to_snowflake_type([col]).get(col),
+            ArrayType,
+        ):
+            return SnowflakeQueryCompiler(
+                self._modin_frame.apply_snowpark_function_to_columns(
+                    lambda col: array_size(col)
+                )
+            )
+        else:
+            return SnowflakeQueryCompiler(
+                self._modin_frame.apply_snowpark_function_to_columns(
+                    lambda col: self._replace_non_str(col, length(col))
+                )
             )
-        )
 
     def str_ljust(self, width: int, fillchar: str = " ") -> None:
         ErrorMessage.method_not_implemented_error("ljust", "Series.str")

tests/integ/modin/series/test_str_accessor.py

@@ -10,8 +10,9 @@
 import pandas as native_pd
 import pytest
 
+from snowflake.snowpark._internal.utils import TempObjectType
 import snowflake.snowpark.modin.plugin  # noqa: F401
-from tests.integ.modin.utils import eval_snowpark_pandas_result
+from tests.integ.modin.utils import assert_series_equal, eval_snowpark_pandas_result
 from tests.integ.utils.sql_counter import sql_count_checker
 
 TEST_DATA = [
@@ -449,6 +450,55 @@ def test_str_len():
     eval_snowpark_pandas_result(snow_ser, native_ser, lambda ser: ser.str.len())
 
 
+@sql_count_checker(query_count=1)
+def test_str_len_list():
+    native_ser = native_pd.Series([["a", "b"], ["c", "d", None], None, []])
+    snow_ser = pd.Series(native_ser)
+    eval_snowpark_pandas_result(snow_ser, native_ser, lambda ser: ser.str.len())
+
+
+@sql_count_checker(query_count=9, udf_count=1)
+def test_str_len_list_coin_base(session):
+    from tests.utils import Utils
+
+    table_name = Utils.random_name_for_temp_object(TempObjectType.TABLE)
+    Utils.create_table(
+        session, table_name, "SHARED_CARD_USERS array", is_temporary=True
+    )
+    session.sql(
+        f"""insert into {table_name} (SHARED_CARD_USERS) SELECT PARSE_JSON('["Apple", "Pear", "Cabbage"]')"""
+    ).collect()
+    session.sql(f"insert into {table_name} values (NULL)").collect()
+
+    df = pd.read_snowflake(table_name)
+
+    def compute_num_shared_card_users(x):
+        """
+        Helper function to compute the number of shared card users
+
+        Input:
+         - x: the array with the users
+
+        Output: Number of shared card users
+        """
+        if x:
+            return len(x)
+        else:
+            return 0
+
+    # The following two methods for computing the final result should be identical.
+
+    # The first one uses `Series.str.len` followed by `Series.fillna`.
+    str_len_res = df["SHARED_CARD_USERS"].str.len().fillna(0)
+
+    # The second one uses `Series.apply` and a user defined function.
+    apply_res = df["SHARED_CARD_USERS"].apply(
+        lambda x: compute_num_shared_card_users(x)
+    )
+
+    assert_series_equal(str_len_res, apply_res, check_dtype=False)
+
+
 @pytest.mark.parametrize(
     "items",
     [