comment changes

moved comments and added new comments

Author: brock-acryl

metadata-ingestion/src/datahub/ingestion/source/sql/sql_common.py

@@ -354,6 +354,8 @@ def __init__(self, config: SQLCommonConfig, ctx: PipelineContext, platform: str)
 
     def _add_default_options(self, sql_config: SQLCommonConfig) -> None:
         """Add default SQLAlchemy options. Can be overridden by subclasses to add additional defaults."""
+        # Extra default SQLAlchemy option for better connection pooling and threading.
+        # https://docs.sqlalchemy.org/en/14/core/pooling.html#sqlalchemy.pool.QueuePool.params.max_overflow
         if sql_config.is_profiling_enabled():
             sql_config.options.setdefault(
                 "max_overflow", sql_config.profiling.max_workers
@@ -526,8 +528,6 @@ def get_workunits_internal(self) -> Iterable[Union[MetadataWorkUnit, SqlWorkUnit
             # Known issue with sqlalchemy https://stackoverflow.com/questions/60804288/pycharm-duplicated-log-for-sqlalchemy-echo-true
             sqlalchemy_log._add_default_handler = lambda x: None  # type: ignore
 
-        # Extra default SQLAlchemy option for better connection pooling and threading.
-        # https://docs.sqlalchemy.org/en/14/core/pooling.html#sqlalchemy.pool.QueuePool.params.max_overflow
         self._add_default_options(sql_config)
 
         for inspector in self.get_inspectors():

metadata-ingestion/src/datahub/ingestion/source/sql/teradata.py

@@ -681,8 +681,10 @@ def __init__(self, config: TeradataConfig, ctx: PipelineContext):
 
     def _add_default_options(self, sql_config: SQLCommonConfig) -> None:
         """Add Teradata-specific default options"""
-        # Teradata does not support max_overflow, instead we use QueuePool when profiling
+        super()._add_default_options(sql_config)
         if sql_config.is_profiling_enabled():
+            # By default, Teradata uses SingletonThreadPool, which is not supported by sqlalchemy
+            # QueuePool used for parallel connections when profiling is enabled
             sql_config.options.setdefault("poolclass", QueuePool)
 
     @classmethod