Add dunder prefix to column aliases for simple-metric inputs (#1938)

To avoid alias conflicts in the generated SQL when a semantic model has
a dimension and a simple metric with the same name, this PR updates the
naming scheme for SQL column aliases. The longer term fix is to add a
validation so that semantic models are required to have unique metric /
measure / entity names.

Due to the large snapshot changes, please view by commit.

Author: plypaul

.changes/unreleased/Fixes-20251117-085411.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: Add dunder prefix to column aliases for simple-metric inputs
+time: 2025-11-17T08:54:11.838469-08:00
+custom:
+  Author: plypaul
+  Issue: "1938"

metricflow-semantics/metricflow_semantics/specs/dunder_column_association_resolver.py

@@ -35,13 +35,13 @@ def resolve_spec(self, spec: InstanceSpec) -> ColumnAssociation:  # noqa: D102
 
 
 class DunderColumnAssociationResolverVisitor(InstanceSpecVisitor[ColumnAssociation]):
-    """Visitor helper class for DefaultColumnAssociationResolver2."""
+    """Visitor helper class for DefaultColumnAssociationResolver."""
 
     def visit_metric_spec(self, metric_spec: MetricSpec) -> ColumnAssociation:  # noqa: D102
         return ColumnAssociation(metric_spec.alias or metric_spec.element_name)
 
     def visit_simple_metric_input_spec(self, spec: SimpleMetricInputSpec) -> ColumnAssociation:  # noqa: D102
-        return ColumnAssociation(spec.element_name)
+        return ColumnAssociation(DUNDER + spec.element_name)
 
     def visit_dimension_spec(self, dimension_spec: DimensionSpec) -> ColumnAssociation:  # noqa: D102
         return ColumnAssociation(dimension_spec.alias or dimension_spec.dunder_name)

metricflow-semantics/metricflow_semantics/test_helpers/semantic_manifest_yamls/name_edge_case_manifest/__init__.py

@@ -0,0 +1,5 @@
+from __future__ import annotations
+
+from metricflow_semantics.test_helpers.config_helpers import DirectoryPathAnchor
+
+NAME_EDGE_CASE_MANIFEST_ANCHOR = DirectoryPathAnchor()

metricflow-semantics/metricflow_semantics/test_helpers/semantic_manifest_yamls/name_edge_case_manifest/metrics.yaml

@@ -0,0 +1,8 @@
+---
+metric:
+  name: conflicted_name
+  description: |
+    Used to test a soon-to-be-deprecated use case where the name of the metric is the same as a dimension.
+  type: simple
+  type_params:
+    measure: booking_value

metricflow-semantics/metricflow_semantics/test_helpers/semantic_manifest_yamls/name_edge_case_manifest/project_configuration.yaml

@@ -0,0 +1 @@
+../shared/project_configuration.yaml

metricflow-semantics/metricflow_semantics/test_helpers/semantic_manifest_yamls/name_edge_case_manifest/semantic_models/bookings_source.yaml

@@ -0,0 +1,26 @@
+---
+semantic_model:
+  name: bookings_source
+  description: bookings_source
+
+  node_relation:
+    schema_name: $source_schema
+    alias: fct_bookings
+
+  defaults:
+    agg_time_dimension: ds
+
+  measures:
+    - name: booking_value
+      agg: sum
+
+  dimensions:
+    - name: conflicted_name
+      expr: "'dummy_dimension_value'"
+      type: categorical
+    - name: ds
+      type: time
+      type_params:
+        time_granularity: day
+
+  primary_entity: booking

tests_metricflow/fixtures/manifest_fixtures.py

@@ -32,6 +32,9 @@
 from metricflow_semantics.test_helpers.semantic_manifest_yamls.multi_hop_join_manifest import (
     MULTI_HOP_JOIN_MANIFEST_ANCHOR,
 )
+from metricflow_semantics.test_helpers.semantic_manifest_yamls.name_edge_case_manifest import (
+    NAME_EDGE_CASE_MANIFEST_ANCHOR,
+)
 from metricflow_semantics.test_helpers.semantic_manifest_yamls.non_sm_manifest import NON_SM_MANIFEST_ANCHOR
 from metricflow_semantics.test_helpers.semantic_manifest_yamls.partitioned_multi_hop_join_manifest import (
     PARTITIONED_MULTI_HOP_JOIN_MANIFEST_ANCHOR,
@@ -130,6 +133,11 @@ class SemanticManifestSetup(Enum):
         id_number_space=IdNumberSpace.for_block(10),
         yaml_file_dir=SIMPLE_MULTI_HOP_JOIN_MANIFEST_ANCHOR.directory,
     )
+    NAME_EDGE_CASE_MANIFEST = SemanticManifestSetupPropertySet(
+        semantic_manifest_name="name_edge_case_manifest",
+        id_number_space=IdNumberSpace.for_block(11),
+        yaml_file_dir=NAME_EDGE_CASE_MANIFEST_ANCHOR.directory,
+    )
 
     @property
     def id_number_space(self) -> IdNumberSpace:  # noqa: D102
@@ -383,3 +391,11 @@ def simple_multi_hop_join_manifest_lookup(
 ) -> SemanticManifestLookup:
     """Manifest used to test ambiguous resolution of group-by-items."""
     return mf_engine_test_fixture_mapping[SemanticManifestSetup.SIMPLE_MULTI_HOP_JOIN_MANIFEST].semantic_manifest_lookup
+
+
+@pytest.fixture(scope="session")
+def name_edge_case_manifest(
+    mf_engine_test_fixture_mapping: Mapping[SemanticManifestSetup, MetricFlowEngineTestFixture]
+) -> SemanticManifestLookup:
+    """Manifest used to test name-related edge cases."""
+    return mf_engine_test_fixture_mapping[SemanticManifestSetup.NAME_EDGE_CASE_MANIFEST].semantic_manifest_lookup

tests_metricflow/query_rendering/test_name_edge_caes.py

@@ -0,0 +1,33 @@
+from __future__ import annotations
+
+from collections.abc import Mapping
+
+import pytest
+from _pytest.fixtures import FixtureRequest
+from metricflow_semantics.test_helpers.config_helpers import MetricFlowTestConfiguration
+
+from metricflow.protocols.sql_client import SqlClient
+from tests_metricflow.fixtures.manifest_fixtures import MetricFlowEngineTestFixture, SemanticManifestSetup
+from tests_metricflow.query_rendering.compare_rendered_query import render_and_check
+
+
+@pytest.mark.sql_engine_snapshot
+@pytest.mark.duckdb_only
+def test_metric_name_same_as_dimension_name(
+    request: FixtureRequest,
+    mf_test_configuration: MetricFlowTestConfiguration,
+    mf_engine_test_fixture_mapping: Mapping[SemanticManifestSetup, MetricFlowEngineTestFixture],
+    sql_client: SqlClient,
+) -> None:
+    """Check a soon-to-be-deprecated use case where a manifest contains a metric with the same name as a dimension."""
+    fixture = mf_engine_test_fixture_mapping[SemanticManifestSetup.NAME_EDGE_CASE_MANIFEST]
+    render_and_check(
+        request=request,
+        mf_test_configuration=mf_test_configuration,
+        dataflow_to_sql_converter=fixture.dataflow_to_sql_converter,
+        sql_client=sql_client,
+        dataflow_plan_builder=fixture.dataflow_plan_builder,
+        query_spec=fixture.query_parser.parse_and_validate_query(
+            metric_names=["conflicted_name"], group_by_names=["booking__conflicted_name"]
+        ).query_spec,
+    )

tests_metricflow/snapshots/test_cli.py/str/test_saved_query_explain__result.txt

@@ -6,14 +6,14 @@ test_filename: test_cli.py
 SELECT
   subq_1.metric_time__day AS metric_time__day
   , customers_src_10000.country AS customer__customer_country
-  , SUM(subq_1.transactions) AS transactions
-  , SUM(subq_1.quick_buy_transactions) AS quick_buy_transactions
+  , SUM(subq_1.__transactions) AS transactions
+  , SUM(subq_1.__quick_buy_transactions) AS quick_buy_transactions
 FROM (
   SELECT
     DATE_TRUNC('day', ds) AS metric_time__day
     , id_customer AS customer
-    , CASE WHEN CASE WHEN transaction_type_name = 'quick-buy' THEN TRUE ELSE FALSE END THEN 1 ELSE 0 END AS quick_buy_transactions
-    , 1 AS transactions
+    , CASE WHEN CASE WHEN transaction_type_name = 'quick-buy' THEN TRUE ELSE FALSE END THEN 1 ELSE 0 END AS __quick_buy_transactions
+    , 1 AS __transactions
   FROM "mf_tutorial"."main"."transactions" transactions_src_10000
 ) subq_1
 LEFT OUTER JOIN

tests_metricflow/snapshots/test_cli_quiet.py/str/test_explain__result.txt

@@ -5,11 +5,11 @@ docstring:
 ---
 SELECT
   metric_time__day
-  , SUM(transactions) AS transactions
+  , SUM(__transactions) AS transactions
 FROM (
   SELECT
     DATE_TRUNC('day', ds) AS metric_time__day
-    , 1 AS transactions
+    , 1 AS __transactions
   FROM "mf_tutorial"."main"."transactions" transactions_src_10000
 ) subq_2
 GROUP BY