When does a transaction start?

[bazile-clyde]

When does a transaction start?

[mwatts15]

A transaction is committed in all of the methods. We call Engine.begin() and pass to a context manager.

We use the 1.4 "legacy" API where the, now deprecated, nesting of begin()/commit() is possible. So, you can get the SQLArchemy engine from the store (or you could have passed it in to the Store's __init__) and call begin() around whatever calls to the store you want. So that changes the transaction boundary.

I think by "avoiding" transactions you mean not calling commit() within the transaction within the Store methods. (My understanding of the Python DB API is that you start a transaction when you execute anything if there isn't already one in progress.) Honestly, I prefer not actually managing the transaction within the store since it becomes complicated to manage when you need the transaction boundary to be broader than the Store can manage (e.g., committing after formatting a response to a web request). I haven't taken up that change since I became maintainer, but, as always, PRs with tests are welcome.

The SQLAlchemy store doesn't implement commit(), so it doesn't do anything if you call it.

SQLAlchemy transactions reference: https://docs.sqlalchemy.org/en/14/core/connections.html?highlight=connect#using-transactions