Use helper function to find matching instance in dataset

metricflow-semantics/metricflow_semantics/instances.py

@@ -49,7 +49,9 @@ class MdoInstance(ABC, Generic[SpecT]):
     @property
     def associated_column(self) -> ColumnAssociation:
         """Helper for getting the associated column until support for multiple associated columns is added."""
-        assert len(self.associated_columns) == 1
+        assert (
+            len(self.associated_columns) == 1
+        ), f"Expected exactly one column for {self.__class__.__name__}, but got {self.associated_columns}"
         return self.associated_columns[0]
 
     def accept(self, visitor: InstanceVisitor[VisitorOutputT]) -> VisitorOutputT:

metricflow/dataset/sql_dataset.py

@@ -1,10 +1,10 @@
 from __future__ import annotations
 
-from typing import List, Optional, Sequence
+from typing import List, Optional, Sequence, Tuple
 
 from dbt_semantic_interfaces.references import SemanticModelReference
 from metricflow_semantics.assert_one_arg import assert_exactly_one_arg_set
-from metricflow_semantics.instances import EntityInstance, InstanceSet
+from metricflow_semantics.instances import EntityInstance, InstanceSet, TimeDimensionInstance
 from metricflow_semantics.mf_logging.lazy_formattable import LazyFormat
 from metricflow_semantics.specs.column_assoc import ColumnAssociation
 from metricflow_semantics.specs.dimension_spec import DimensionSpec
@@ -122,30 +122,33 @@ def column_association_for_dimension(
 
         return column_associations_to_return[0]
 
-    def column_association_for_time_dimension(
-        self,
-        time_dimension_spec: TimeDimensionSpec,
-    ) -> ColumnAssociation:
-        """Given the name of the time dimension, return the set of columns associated with it in the data set."""
+    def instances_for_time_dimensions(
+        self, time_dimension_specs: Sequence[TimeDimensionSpec]
+    ) -> Tuple[TimeDimensionInstance, ...]:
+        """Return the instances associated with these specs in the data set."""
+        time_dimension_specs_set = set(time_dimension_specs)
         matching_instances = 0
-        column_associations_to_return = None
+        instances_to_return: Tuple[TimeDimensionInstance, ...] = ()
         for time_dimension_instance in self.instance_set.time_dimension_instances:
-            if time_dimension_instance.spec == time_dimension_spec:
-                column_associations_to_return = time_dimension_instance.associated_columns
+            if time_dimension_instance.spec in time_dimension_specs_set:
+                instances_to_return += (time_dimension_instance,)
                 matching_instances += 1
 
-        if matching_instances > 1:
+        if matching_instances != len(time_dimension_specs_set):
             raise RuntimeError(
-                f"More than one time dimension instance with spec {time_dimension_spec} in "
-                f"instance set: {self.instance_set}"
+                f"Unexpected number of time dimension instances found matching specs.\nSpecs: {time_dimension_specs_set}\n"
+                f"Instances: {instances_to_return}"
             )
 
-        if not column_associations_to_return:
-            raise RuntimeError(
-                f"No time dimension instances with spec {time_dimension_spec} in instance set: {self.instance_set}"
-            )
+        return instances_to_return
 
-        return column_associations_to_return[0]
+    def instance_for_time_dimension(self, time_dimension_spec: TimeDimensionSpec) -> TimeDimensionInstance:
+        """Given the name of the time dimension, return the instance associated with it in the data set."""
+        return self.instances_for_time_dimensions((time_dimension_spec,))[0]
+
+    def column_association_for_time_dimension(self, time_dimension_spec: TimeDimensionSpec) -> ColumnAssociation:
+        """Given the name of the time dimension, return the set of columns associated with it in the data set."""
+        return self.instance_for_time_dimension(time_dimension_spec).associated_column
 
     @property
     @override

metricflow/plan_conversion/dataflow_to_sql.py

@@ -1470,16 +1470,8 @@ def visit_join_to_time_spine_node(self, node: JoinToTimeSpineNode) -> SqlDataSet
             self._column_association_resolver, OrderedDict({parent_alias: parent_instance_set})
         )
 
-        # Select matching instance from time spine data set (using base grain - custom grain will be joined in a later node).
-        original_time_spine_dim_instance: Optional[TimeDimensionInstance] = None
-        for time_dimension_instance in time_spine_dataset.instance_set.time_dimension_instances:
-            if time_dimension_instance.spec == agg_time_dimension_instance_for_join.spec:
-                original_time_spine_dim_instance = time_dimension_instance
-                break
-        assert original_time_spine_dim_instance, (
-            "Couldn't find requested agg_time_dimension_instance_for_join in time spine data set, which "
-            f"indicates it may have been configured incorrectly. Expected: {agg_time_dimension_instance_for_join.spec};"
-            f" Got: {[instance.spec for instance in time_spine_dataset.instance_set.time_dimension_instances]}"
+        original_time_spine_dim_instance = time_spine_dataset.instance_for_time_dimension(
+            agg_time_dimension_instance_for_join.spec
         )
         time_spine_column_select_expr: Union[
             SqlColumnReferenceExpression, SqlDateTruncExpression
@@ -1590,17 +1582,10 @@ def visit_join_to_custom_granularity_node(self, node: JoinToCustomGranularityNod
 
         # New dataset will be joined to parent dataset without a subquery, so use the same FROM alias as the parent node.
         parent_alias = parent_data_set.checked_sql_select_node.from_source_alias
-        parent_time_dimension_instance: Optional[TimeDimensionInstance] = None
-        for instance in parent_data_set.instance_set.time_dimension_instances:
-            if instance.spec == node.time_dimension_spec.with_base_grain():
-                parent_time_dimension_instance = instance
-                break
-        parent_column: Optional[SqlSelectColumn] = None
-        assert parent_time_dimension_instance, (
-            "JoinToCustomGranularityNode's expected time_dimension_spec not found in parent dataset instances. "
-            f"This indicates internal misconfiguration. Expected: {node.time_dimension_spec.with_base_grain()}; "
-            f"Got: {[instance.spec for instance in parent_data_set.instance_set.time_dimension_instances]}"
+        parent_time_dimension_instance = parent_data_set.instance_for_time_dimension(
+            node.time_dimension_spec.with_base_grain()
         )
+        parent_column: Optional[SqlSelectColumn] = None
         for select_column in parent_data_set.checked_sql_select_node.select_columns:
             if select_column.column_alias == parent_time_dimension_instance.associated_column.column_name:
                 parent_column = select_column