ashb commented on a change in pull request #10956:
URL: https://github.com/apache/airflow/pull/10956#discussion_r499532425
##########
File path: airflow/utils/sqlalchemy.py
##########
@@ -141,3 +142,107 @@ def skip_locked(session: Session) -> Dict[str, Any]:
return {'skip_locked': True}
else:
return {}
+
+
+def nowait(session: Session) -> Dict[str, Any]:
+ """
+ Return kwargs for passing to `with_for_update()` suitable for the current
DB engine version.
+
+ We do this as we document the fact that on DB engines that don't support
this construct, we do not
+ support/recommend running HA scheduler. If a user ignores this and tries
anyway everything will still
+ work, just slightly slower in some circumstances.
+
+ Specifically don't emit NOWAIT for MySQL < 8, or MariaDB, neither of which
support this construct
+
+ See https://jira.mariadb.org/browse/MDEV-13115
+ """
+ dialect = session.bind.dialect
+
+ if dialect.name != "mysql" or dialect.supports_for_update_of:
+ return {'nowait': True}
+ else:
+ return {}
+
+
+def nulls_first(col, session: Session) -> Dict[str, Any]:
+ """
+ Adds a nullsfirst construct to the column ordering. Currently only
Postgres supports it.
+ In MySQL & Sqlite NULL values are considered lower than any non-NULL
value, therefore, NULL values
+ appear first when the order is ASC (ascending)
+ """
+ if session.bind.dialect.name == "postgresql":
+ return nullsfirst(col)
+ else:
+ return col
+
+
+USE_ROW_LEVEL_LOCKING: bool = conf.getboolean('scheduler',
'use_row_level_locking', fallback=True)
+
+
+def with_for_update(query, **kwargs):
Review comment:
I named it the same on purpose, as it mirrors the underlying method, but
I see your point
How about `with_row_locks`?
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
[email protected]
