ntkathole · May 3, 2026 · May 1, 2026 · May 2, 2026 · May 2, 2026 · May 2, 2026
@@ -33,6 +33,7 @@
 from pyspark.sql import SparkSession
 
 from feast import FeatureView, OnDemandFeatureView
+from feast.batch_feature_view import BatchFeatureView
 from feast.data_source import DataSource
 from feast.dataframe import DataFrameEngine, FeastDataFrame
 from feast.errors import EntitySQLEmptyResults, InvalidEntityType
@@ -260,6 +261,10 @@ def get_historical_features(
             entity_df_event_timestamp_range,
         )
 
+        query_context = _apply_bfv_transformations(
+            spark_session, feature_views, query_context
+        )
+
         spark_query_context = [
             SparkFeatureViewQueryContext(
                 **asdict(context),
@@ -713,6 +718,52 @@ def _entity_schema_keys_from(
     )
 
 
+def _apply_bfv_transformations(
+    spark_session: SparkSession,
+    feature_views: List[FeatureView],
+    query_contexts: List[offline_utils.FeatureViewQueryContext],
+) -> List[offline_utils.FeatureViewQueryContext]:
+    """
+    For BatchFeatureViews with a UDF, read the raw source into a Spark DataFrame,
+    invoke the transformation, register the result as a temp view, and replace the
+    table_subquery in the query context so the PIT join reads transformed data.
+    """
+    from dataclasses import replace
+
+    from feast.feature_view_utils import (
+        get_transformation_function,
+        has_transformation,
+        resolve_feature_view_source,
+    )
+
+    fv_by_name = {fv.projection.name_to_use(): fv for fv in feature_views}
+
+    updated_contexts = []
+    for ctx in query_contexts:
+        fv = fv_by_name.get(ctx.name)
+        if (
+            fv is not None
+            and isinstance(fv, BatchFeatureView)
+            and has_transformation(fv)
+        ):
+            udf = get_transformation_function(fv)
+            if udf is not None:
+                source_info = resolve_feature_view_source(fv)
+                source_query = source_info.data_source.get_table_query_string()
+                source_df = spark_session.sql(f"SELECT * FROM {source_query}")
+
+                transformed_df = udf(source_df)
+
+                tmp_view_name = f"__feast_bfv_{fv.name}_{uuid.uuid4().hex[:8]}"
+                transformed_df.createOrReplaceTempView(tmp_view_name)
+
+                ctx = replace(ctx, table_subquery=tmp_view_name)
+
+        updated_contexts.append(ctx)
+
+    return updated_contexts
+
+
 def _get_entity_df_event_timestamp_range(
     entity_df: Union[pd.DataFrame, str],
     entity_df_event_timestamp_col: str,

@@ -0,0 +1,193 @@
+"""
+Unit tests for BFV compute-on-read in SparkOfflineStore.get_historical_features().
+
+Verifies that BatchFeatureViews with a UDF have their transformation applied
+during get_historical_features(), with the transformed DataFrame registered as
+a temp view that replaces the raw table_subquery in the PIT join.
+"""
+
+from dataclasses import replace
+from unittest.mock import MagicMock
+
+import pytest
+
+from feast.batch_feature_view import BatchFeatureView
+from feast.feature_view import FeatureView
+from feast.infra.offline_stores import offline_utils
+from feast.infra.offline_stores.contrib.spark_offline_store.spark import (
+    _apply_bfv_transformations,
+)
+from feast.infra.offline_stores.contrib.spark_offline_store.spark_source import (
+    SparkSource,
+)
+from feast.transformation.base import Transformation
+
+
+@pytest.fixture()
+def spark_session():
+    mock = MagicMock()
+    mock.sql.return_value = MagicMock(name="source_df")
+    return mock
+
+
+@pytest.fixture()
+def spark_source():
+    source = MagicMock(spec=SparkSource)
+    source.get_table_query_string.return_value = "`raw_events`"
+    return source
+
+
+@pytest.fixture()
+def base_query_context():
+    return offline_utils.FeatureViewQueryContext(
+        name="my_bfv",
+        ttl=3600,
+        entities=["user_id"],
+        features=["avg_rating"],
+        field_mapping={},
+        timestamp_field="event_timestamp",
+        created_timestamp_column=None,
+        table_subquery="`raw_events`",
+        entity_selections=["user_id AS user_id"],
+        min_event_timestamp="2023-01-01T00:00:00",
+        max_event_timestamp="2024-01-01T00:00:00",
+        date_partition_column=None,
+    )
+
+
+def _make_bfv(name: str, spark_source, has_udf: bool = True):
+    """Create a mock BatchFeatureView with optional UDF."""
+    fv = MagicMock(spec=BatchFeatureView)
+    fv.name = name
+    fv.projection = MagicMock()
+    fv.projection.name_to_use.return_value = name
+    fv.batch_source = spark_source
+    fv.source_views = []
+
+    if has_udf:
+        transformation = MagicMock(spec=Transformation)
+        transformed_df = MagicMock(name="transformed_df")
+        transformation.udf = MagicMock(return_value=transformed_df)
+        fv.feature_transformation = transformation
+        fv.udf = transformation.udf
+    else:
+        fv.feature_transformation = None
+        fv.udf = None
+
+    return fv
+
+
+def _make_plain_fv(name: str, spark_source):
+    """Create a mock plain FeatureView (not a BatchFeatureView)."""
+    fv = MagicMock(spec=FeatureView)
+    fv.name = name
+    fv.projection = MagicMock()
+    fv.projection.name_to_use.return_value = name
+    fv.batch_source = spark_source
+    fv.feature_transformation = None
+    fv.udf = None
+    return fv
+
+
+class TestApplyBfvTransformations:
+    def test_bfv_with_udf_replaces_table_subquery(
+        self, spark_session, spark_source, base_query_context
+    ):
+        """BFV with a UDF should have its table_subquery replaced with a temp view."""
+        bfv = _make_bfv("my_bfv", spark_source)
+        contexts = [base_query_context]
+
+        result = _apply_bfv_transformations(spark_session, [bfv], contexts)
+
+        assert len(result) == 1
+        assert result[0].table_subquery != "`raw_events`"
+        assert result[0].table_subquery.startswith("__feast_bfv_my_bfv_")
+
+    def test_bfv_udf_is_invoked_with_source_df(
+        self, spark_session, spark_source, base_query_context
+    ):
+        """The UDF should be called with the DataFrame read from the raw source."""
+        bfv = _make_bfv("my_bfv", spark_source)
+        contexts = [base_query_context]
+
+        _apply_bfv_transformations(spark_session, [bfv], contexts)
+
+        spark_session.sql.assert_called_once_with("SELECT * FROM `raw_events`")
+        source_df = spark_session.sql.return_value
+        bfv.feature_transformation.udf.assert_called_once_with(source_df)
+
+    def test_transformed_df_registered_as_temp_view(
+        self, spark_session, spark_source, base_query_context
+    ):
+        """The transformed DataFrame should be registered as a temp view."""
+        bfv = _make_bfv("my_bfv", spark_source)
+        transformed_df = bfv.feature_transformation.udf.return_value
+        contexts = [base_query_context]
+
+        result = _apply_bfv_transformations(spark_session, [bfv], contexts)
+
+        transformed_df.createOrReplaceTempView.assert_called_once()
+        view_name = transformed_df.createOrReplaceTempView.call_args[0][0]
+        assert view_name == result[0].table_subquery
+
+    def test_plain_feature_view_unchanged(
+        self, spark_session, spark_source, base_query_context
+    ):
+        """Plain FeatureViews (not BFV) should pass through without modification."""
+        fv = _make_plain_fv("my_bfv", spark_source)
+        contexts = [base_query_context]
+
+        result = _apply_bfv_transformations(spark_session, [fv], contexts)
+
+        assert result[0].table_subquery == "`raw_events`"
+        spark_session.sql.assert_not_called()
+
+    def test_bfv_without_udf_unchanged(
+        self, spark_session, spark_source, base_query_context
+    ):
+        """BFV without a UDF should pass through without modification."""
+        bfv = _make_bfv("my_bfv", spark_source, has_udf=False)
+        contexts = [base_query_context]
+
+        result = _apply_bfv_transformations(spark_session, [bfv], contexts)
+
+        assert result[0].table_subquery == "`raw_events`"
+        spark_session.sql.assert_not_called()
+
+    def test_mixed_views_only_transforms_bfvs(
+        self, spark_session, spark_source, base_query_context
+    ):
+        """With mixed BFV and plain FVs, only BFVs with UDFs get transformed."""
+        bfv = _make_bfv("my_bfv", spark_source)
+        plain_fv = _make_plain_fv("plain_fv", spark_source)
+
+        ctx_bfv = base_query_context
+        ctx_plain = replace(
+            base_query_context,
+            name="plain_fv",
+            features=["some_feature"],
+        )
+
+        result = _apply_bfv_transformations(
+            spark_session, [bfv, plain_fv], [ctx_bfv, ctx_plain]
+        )
+
+        assert result[0].table_subquery.startswith("__feast_bfv_my_bfv_")
+        assert result[1].table_subquery == "`raw_events`"
+
+    def test_other_context_fields_preserved(
+        self, spark_session, spark_source, base_query_context
+    ):
+        """All fields besides table_subquery should remain unchanged."""
+        bfv = _make_bfv("my_bfv", spark_source)
+        contexts = [base_query_context]
+
+        result = _apply_bfv_transformations(spark_session, [bfv], contexts)
+
+        assert result[0].name == base_query_context.name
+        assert result[0].ttl == base_query_context.ttl
+        assert result[0].entities == base_query_context.entities
+        assert result[0].features == base_query_context.features
+        assert result[0].timestamp_field == base_query_context.timestamp_field
+        assert result[0].min_event_timestamp == base_query_context.min_event_timestamp
+        assert result[0].max_event_timestamp == base_query_context.max_event_timestamp