migrate from ZODB 3.3.1 --- to where, and how?

[Tim Peters]

[Harald Armin Massa]
> I am using ZODB "standalone" in version 3.3.1 within some application.
>
> Now I learn that the 3.3.x branch of ZODB is "retired". No problem so
> far, everything is running fine.
>
> BUT... "retired" gives me the hint that nothing GREAT will be done to
> this branch anymore :)

More than that, there will never be another release of any kind in the
3.3 line.  ZODB work (I'm ZODB's primary maintainer, BTW) is driven by
Zope's needs.  When the last Zope that needs a particular ZODB is no
longer supported, the ZODB used by that Zope is also no longer
supported.  The ZODB 3.1 and 3.3 lines are dead now, corresponding
(respectively) to the Zope 2.6 line and an early experimental release
of Zope3.

> Now I am questioning myself: to which branch should I migrate? Is 3.5 a
> sure bet, or are uneven subversions a bad sign, making retirement
> likely?

Whether digits in a release number are even or odd has no meaning in
ZODB (or Zope) releases.

You should be able to move to the 3.4 or 3.5 lines without problems. 
ZODB 3.4 corresponds to the Zope 2.8 line, and ZODB 3.5 to the Zope
3.1 line.  By the end of this year, ZODB 3.6 will be released
(corresponding to Zopes 2.9 and 3.2, which will also be released by
the end of the year).  ZODB 3.7 (along with another batch of Zopes)
will be released mid-year 2006, etc.

> As much as my diggings showed me, the "special sign" of 3.3 was
> import ZODB
> from persistent import Persistent
> from persistent.list import PersistentList
> from persistent.mapping import PersistentMapping
>
> that PersistentList and PersistenMapping reside within
> persistent.<something>, while in the 3.2 branch they reside somewhere
> else in the namespace.

ZODBs at and before the 3.2 line differ in many ways from ZODBs at and
after the 3.3 line.  So far, the 3.3, 3.4, 3.5 and (not yet released)
3.6 lines are pretty much intechangeable (although, of course, later
releases add features that may not work under earlier releases, and
because the 3.3 line is dead now it doesn't even get critical bugfixes
anymore).

> I learned it the hard way that 3.3 filestores not get converted
> magically or easy to 3.2 :)

As above, many things changed starting with 3.3.

> So, my questions:
>  - where should I migrate to?

I'd jump to 3.5.1 now if I were you, and to 3.6.0 when it's released.

>  - how is migration done best (especially taking care of "old"
> filestores

Moving from 3.3.1 to 3.5.1 should "just work".

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