Mark Miller wrote:
I'm inclined to agree to a large extent. If we want to remove
deprecations more often, why not release major versions more often?
The main ramification I see being that the index back compat period
could be significantly shortened time wise with the current policy.
I don't think that there is a requirement that 5.x, or later, *must not*
be able to read 3.x. It is merely an allowance.
Conversely, the side effect of using minor releases as major ones is
that we indefinitely postpone the allowable breaking of index
compatibility. With this proposal, what would ever drive a 4.0 release?
-- DM
DM Smith wrote:
Michael Busch wrote:
Probably everyone is thinking right now "Oh no! Not again!". I admit I
didn't fully read the incredibly long recent thread about
backwards-compatibility, so maybe what I'm about to propose has been
proposed already. In that case my apologies in advance.
Perhaps you should go back and see why the thread died. The points I
made earlier, at the end of the thread, are still pertinent. I'll
highlight some of that again.
Rather than discussing our current backwards-compatibility policy
again, I'd like to make here a concrete proposal for changing the
policy
after Lucene 3.0 is released.
I'll call X.Y -> X+1.0 a 'major release', X.Y -> X.Y+1 a
'minor release' and X.Y.Z -> X.Y.Z+1 a 'bugfix release'. (we can later
use different names; just for convenience here...)
1. The file format backwards-compatiblity policy will remain unchanged;
i.e. Lucene X.Y supports reading all indexes written with Lucene
X-1.Y. That means Lucene 4.0 will not have to be able to read 2.x
indexes.
I'll reiterate what this means to me. It is more than just file
format stability. An index must still be useful. An index is
invalidated if the analyzers, filters and/or token streams produce a
different result. If these change, the index is not really readable.
2. Deprecated public and protected APIs can be removed if they have
been released in at least one major or minor release. E.g. an 3.1
API can be released as deprecated in 3.2 and removed in 3.3 or 4.0
(if 4.0 comes after 3.2).
To support #2, in view of #1, we need robust test cases that focus on
input and output of the invariants of analyzers, filters and token
streams. We may already have this.
Regarding #1 and #2, I think that bug fixes should not be held back
when it changes these outputs.
I'll reiterate here too. This will cause Linux distributions, such as
Debian, to number Lucene differently. This will cause confusion.
The Debian policy is to bump the major revision number every time
there is an incompatible API change.
This really is not necessary. We already have a sufficient mechanism
to do #2: just do a major release. But it requires frequent releases.
3. No public or protected APIs are changed in a bugfix release; except
if a severe bug can't be changed otherwise.
Just as important as the signatures, the input/output relationships
should not change, except to fix an undebatable bug.
4. Each release will have release notes with a new section
"Incompatible changes", which lists, as the names says, all
changes that
break backwards compatibility. The list should also have information
about how to convert to the new API. I think the eclipse releases
have such a release notes section.
The big change here apparently is 2. Consider the current situation:
We can release e.g. the new TokenStream API with 2.9; then we can
remove it a month later in 3.0, while still complying with our current
backwards-compatibility policy. A transition period of one month is
very short for such an important API. On the other hand, a transition
period of presumably >2 years, until 4.0 is released, seems very long
to stick with a deprecated API that clutters the APIs and docs. With
the proposed change, we couldn't do that. Given our current release
schedule, the transition period would at least be 6-9 months, which
seems a very reasonable timeframe.
We should also not consider 2. as a must. I.e. we don't *have* to
deprecate after one major or minor release already. We could for a
very popular API like the TokenStream API send a mail to java-user,
asking if people need more transition time and be flexible.
I think this policy is much more dynamic and flexible, but should
still give our users enough confidence. It also removes the need to
do things just for the sake of the current policy rather than because
they make the most sense, like our somewhat goofy X.9 releases. :)
Just to make myself clear: I think we should definitely stick with our
2.9 and 3.0 plans and change the policy afterwards.
My +1 to all 4 points above.
-Michael
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