[ZODB-Dev] Subtransaction backward compatibility

[Tim Peters]

[Dieter Maurer]
> Subtransactions used to be used for two purposes:
>
>   *  ensure that newly created objects get "_p_" attributes
>      (especially "_p_jar" and "_p_oid")
>
>   *  release memory in the mid of large transactions
>      (i.e. reading and/or writing large amounts of objects)
>
> With ZODB 3.4, subtransactions are implemented as savepoints. They can
> still be used for the first purpose. But, they no longer start cache
> garbage collection.

Jim, was the latter intentional?  It surprised me when Dieter pointed it
out, and in the ZODB NEWS file I explicitly implied <wink> otherwise.