Spanner: database.transaction() does not work anymore

[wawrencelu]

Hi, the docs state that I can start a transaction like so: https://googlecloudplatform.github.io/google-cloud-python/latest/spanner/transaction-usage.html#use-a-transaction-as-a-context-manager

with database.transaction() as transaction:

However, when I call it I receive an error saying that transaction attribute does not exist on the database object. Looking at the source, it looks like that method no longer exists either.

Why was it removed? Can we re-add it? Happy to submit a patch to do so.

[tseaver]

@wawrencelu a Transaction instance is bound to a Session, not to the Database. We should just remove any mention of Database.transaction() from the docs, and show it as being used from within a session instead.

Or we could just remove the examples which show manual use of the Transaction: the preferred mode is to use Database.run_in_transaction(), because it handles the complicated retry-on-abort logic. @snehashah16, which would you prefer?

[snehashah16]

Sure, we can reference all docs (all mentions) to point to Database.run_in_transaction()

hopefully there are useful snippets on the manual usage just if a specific usecase exists

[tseaver]

@snehashah16 #6032 leaves the manual snippets in place, but sets them off with notes pointing to run_in_transaction.