How to avoid caching in sqlalchemy?

Question

I have a problem with SQL Alchemy - my app works as a constantly working python application.

I have function like this:

def myFunction(self, param1):
   s = select([statsModel.c.STA_ID, statsModel.c.STA_DATE)])\
                        .select_from(statsModel)

   statsResult = self.connection.execute(s).fetchall()

   return {'result': statsResult, 'calculation': param1}

I think this is clear example - one result set is fetched from database, second is just passed as argument.

The problem is that when I change data in my database, this function still returns data like nothing was changed. When I change data in input parameter, returned parameter "calculation" has proper value.

When I restart the app server, situation comes back to normal - new data are fetched from MySQL.

I know that there were several questions about SQLAlchemy caching like:

How to disable caching correctly in Sqlalchemy orm session?

How to disable SQLAlchemy caching?

but how other can I call this situation? It seems SQLAlchemy keeps the data fetched before and does not perform new queries until application restart. How can I avoid such behavior?

Answer 1

Calling session.expire_all() will evict all database-loaded data from the session. Any access of object attributes subsequent emits a new SELECT statement and gets new data back. Please see http://docs.sqlalchemy.org/en/latest/orm/session_state_management.html#refreshing-expiring for background.

If you still see so-called "caching" after calling expire_all(), then you need to close out transactions as described in my answer linked above.