Make SqlTable.schema_name optional (#1458)

This PR makes `SqlTable.schema_name` optional as `SqlTable` can later be
used to reference a CTE, which does not have a schema name.

metricflow-semantics/metricflow_semantics/sql/sql_table.py

@@ -2,23 +2,28 @@
 
 from dataclasses import dataclass
 from enum import Enum
-from typing import Optional, Tuple, Union
+from typing import Optional
 
 
 class SqlTableType(Enum):  # noqa: D101
     TABLE = "table"
     VIEW = "view"
+    # CTE type may be added later.
 
 
 @dataclass(frozen=True, order=True)
 class SqlTable:
     """Represents a reference to a SQL table."""
 
-    schema_name: str
+    schema_name: Optional[str]
     table_name: str
     db_name: Optional[str] = None
     table_type: SqlTableType = SqlTableType.TABLE
 
+    def __post_init__(self) -> None:  # noqa: D105
+        if self.db_name is not None and self.schema_name is None:
+            raise ValueError(f"{self.db_name=} when it should be specified with {self.schema_name=}")
+
     @staticmethod
     def from_string(sql_str: str) -> SqlTable:  # noqa: D102
         sql_str_split = sql_str.split(".")
@@ -34,14 +39,11 @@ def from_string(sql_str: str) -> SqlTable:  # noqa: D102
     @property
     def sql(self) -> str:
         """Return the snippet that can be used for use in SQL queries."""
-        if self.db_name:
-            return f"{self.db_name}.{self.schema_name}.{self.table_name}"
-        return f"{self.schema_name}.{self.table_name}"
-
-    @property
-    def parts_tuple(self) -> Union[Tuple[str, str], Tuple[str, str, str]]:
-        """Return a tuple of the sql table parts."""
-        if self.db_name:
-            return (self.db_name, self.schema_name, self.table_name)
-        else:
-            return (self.schema_name, self.table_name)
+        items = []
+        if self.db_name is not None:
+            items.append(self.db_name)
+        if self.schema_name is not None:
+            items.append(self.schema_name)
+        items.append(self.table_name)
+
+        return ".".join(items)

metricflow-semantics/metricflow_semantics/time/time_spine_source.py

@@ -24,7 +24,7 @@ class TimeSpineSource:
     Dates should be contiguous. May also contain custom granularity columns.
     """
 
-    schema_name: str
+    schema_name: Optional[str]
     table_name: str = "mf_time_spine"
     # Name of the column in the table that contains date/time values that map to a standard granularity.
     base_column: str = "ds"

metricflow-semantics/tests_metricflow_semantics/sql/test_sql_table.py

@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+import pytest
+from metricflow_semantics.sql.sql_table import SqlTable
+
+
+def test_sql_table() -> None:  # noqa: D103
+    assert SqlTable(schema_name=None, table_name="table", db_name=None).sql == "table"
+    assert SqlTable(schema_name="schema", table_name="table", db_name=None).sql == "schema.table"
+    assert SqlTable(schema_name="schema", table_name="table", db_name="db").sql == "db.schema.table"
+
+    with pytest.raises(ValueError):
+        SqlTable(schema_name=None, table_name="table", db_name="db")

metricflow/sql/sql_column.py

@@ -35,7 +35,7 @@ def db_name(self) -> Optional[str]:  # noqa: D102
         return self.table.db_name
 
     @property
-    def schema_name(self) -> str:  # noqa: D102
+    def schema_name(self) -> Optional[str]:  # noqa: D102
         return self.table.schema_name
 
     @property