Move node dataset resolver subquery ids into a separate namespace

The DataflowPlanNodeOutputDataSetResolver class extends the
DataflowToSqlQueryPlanConverter class. As a result, both classes
effectively do a full conversion from a DataflowPlan to a SqlQueryPlan,
complete with SqlQueryPlan node_id generation. These shared the
same ID prefix, which meant any call that might trigger an additional
invocation of the node dataset resolver subclass could cause shifts
in the subquery IDs in our SqlQueryPlan outputs even if the invocation
had no material impact on the query in question.

In order to reduce snapshot thrash and make our subquery IDs easier to
reason about on read-through of the generated SQL, this change splits
the node dataset resolver ID prefix into a dedicated value.

metricflow-semantics/metricflow_semantics/dag/id_prefix.py

@@ -99,6 +99,7 @@ class StaticIdPrefix(IdPrefix, Enum, metaclass=EnumMetaClassHelper):
 
     TIME_SPINE_SOURCE = "time_spine_src"
     SUB_QUERY = "subq"
+    NODE_RESOLVER_SUB_QUERY = "nr_subq"
 
     @property
     @override

metricflow/dataflow/builder/node_data_set.py

@@ -2,8 +2,11 @@
 
 from typing import TYPE_CHECKING, Dict, Optional, Sequence
 
+from metricflow_semantics.dag.id_prefix import StaticIdPrefix
+from metricflow_semantics.dag.sequential_id import SequentialIdGenerator
 from metricflow_semantics.mf_logging.runtime import log_block_runtime
 from metricflow_semantics.specs.column_assoc import ColumnAssociationResolver
+from typing_extensions import override
 
 from metricflow.dataflow.dataflow_plan import (
     DataflowPlanNode,
@@ -93,3 +96,11 @@ def copy(self) -> DataflowPlanNodeOutputDataSetResolver:
             semantic_manifest_lookup=self._semantic_manifest_lookup,
             _node_to_output_data_set=dict(self._node_to_output_data_set),
         )
+
+    @override
+    def _next_unique_table_alias(self) -> str:
+        """Return the next unique table alias to use in generating queries.
+
+        This uses a separate prefix in order to minimize subquery ID thrash.
+        """
+        return SequentialIdGenerator.create_next_id(StaticIdPrefix.NODE_RESOLVER_SUB_QUERY).str_value