Eng 5808 fix introspect databricks (#96)

Author: James Robinson

noteable_magics/sql/meta_commands.py

@@ -17,6 +17,7 @@
 from sqlalchemy import inspect
 from sqlalchemy.engine.reflection import Inspector
 from sqlalchemy.exc import NoSuchTableError
+from sqlalchemy.types import TypeEngine
 
 from noteable_magics.sql.connection import Connection
 from noteable_magics.sql.gate_messaging_types import (
@@ -424,11 +425,7 @@ def run(self, invoked_as: str, args: List[str]) -> Tuple[DataFrame, bool]:
             names.append(col['name'])
 
             # Convert the possibly db-centric TypeEngine instance to a sqla-generic type string
-            try:
-                type_name = str(col['type'].as_generic()).lower()
-            except NotImplementedError:
-                # ENG-5268: More esoteric types like UUID do not implement .as_generic()
-                type_name = str(col['type']).replace('()', '').lower()
+            type_name = determine_column_type_name(col['type'])
 
             types.append(type_name)
             nullables.append(col['nullable'])
@@ -805,11 +802,7 @@ def introspect_columns(
         for col in column_dicts:
             comment = col.get('comment')  # Some dialects do not return.
 
-            try:
-                type_name = str(col['type'].as_generic()).lower()
-            except NotImplementedError:
-                # ENG-5268: More esoteric types like UUID do not implement .as_generic()
-                type_name = str(col['type']).replace('()', '').lower()
+            type_name = determine_column_type_name(col['type'])
 
             retlist.append(
                 ColumnModel(
@@ -1297,6 +1290,19 @@ def _raise_from_no_such_table(schema: str, relation_name: str):
     raise MetaCommandException(msg)
 
 
+def determine_column_type_name(sqla_column_type_object: TypeEngine) -> str:
+    """Convert the possibly db-centric TypeEngine instance to a sqla-generic type string"""
+    try:
+        type_name = str(sqla_column_type_object.as_generic()).lower()
+    except (NotImplementedError, AssertionError):
+        # ENG-5268: More esoteric types like UUID do not implement .as_generic()
+        # ENG-5808: Some Databricks types are not fully implemented and fail
+        # assertions within .as_generic()
+        type_name = str(sqla_column_type_object).replace('()', '').lower()
+
+    return type_name
+
+
 def make_introspection_error_human_presentable(exception: Exception) -> str:
     """Convert any exception encountered by introspection into database into a nice human presentable string."""