Ahh ok, the semantics confuse me. I thought of experimental as "we're not yet sure how this thingy will evolve or what it'll turn in to - so feel free to play w/ it but don't count on the API or behavior too much". While 'internal' is more like "we need this public for Lucene internal usage, but we don't commit to its API".

I guess SegmentInfos is somewhere in the middle. I.e., there's nothing experimental about it, but it's not public for just Lucene use ... I'll avoid suggesting another tag name :). I'm fine w/ experimental then.

I'll work on it soon.

Shai

On Sun, Feb 28, 2010 at 6:48 PM, Michael McCandless <lucene@mikemccandless.com> wrote:
This class is @lucene.experimental, so we are free to break it.  +1 to
not "extends Vector".

I don't think we should change to @lucene.internal.... since the
thinking is apps outside Lucene should be able to introspect and see
segment structure in the index.  Ie we made this API public so people
outside could call it, but it's experimental so we are free to break
things.

Mike

On Sun, Feb 28, 2010 at 10:41 AM, Shai Erera <serera@gmail.com> wrote:
> Ok agreed. I'll do some code investigation and then open an issue. I think
> that back-compat with this class should not be a (big) problem ... but then
> - I always think that :).
> Shai
>
> On Sun, Feb 28, 2010 at 4:04 PM, Uwe Schindler <uwe@thetaphi.de> wrote:
>>
>> Hi Shai,
>>
>>
>>
>> I am only the Generics Police but not the Generics Homeland Security and
>> also not the Backwards Homeland Security J I think if we break backwards,
>> lets break it complete and remove the “extends Vector”. And then let’s make
>> the Iterator/Iterable/Collection unmodifiable. That would get a big +1 from
>> my side.
>>
>>
>>
>> -----
>>
>> Uwe Schindler
>>
>> H.-H.-Meier-Allee 63, D-28213 Bremen
>>
>> http://www.thetaphi.de
>>
>> eMail: uwe@thetaphi.de
>>
>>
>>
>> From: Shai Erera [mailto:serera@gmail.com]
>> Sent: Sunday, February 28, 2010 2:22 PM
>>
>> To: java-dev@lucene.apache.org
>> Subject: Re: SegmentInfos extends Vector
>>
>>
>>
>> Ok so just that I'm cleared - unmodifiable you mean for iteration only
>> right?
>>
>> And .. do you agree then to refactor the class, or prefer to keep it like
>> that? If you agree, then we need to think if we do that by introducing a new
>> class, or modify the existing one breaking back-compat. A new class is
>> problematic since that will lead to a series of deprecations throughout the
>> code. So I prefer modifying the current one.
>>
>> DM - I've traced Vector.remove all the way back to 1.3, and AbstractList
>> exists since 1.2 (so it's javadocs states), so I think remove has been
>> around always.
>>
>> Shai
>>
>> On Sun, Feb 28, 2010 at 3:14 PM, Uwe Schindler <uwe@thetaphi.de> wrote:
>>
>> I meant it was supported by the API, but if you called the modification
>> methods of SegmentInfos you may have corrupted the contents. So implementing
>> List<?> or Collection<?> just throwing UOE is fine, as modifying in
>> Collections can disabled by that exception, the docs state that.
>>
>>
>>
>> But you are right, it does not make real sense. With backwards
>> compatibility I think of plug-in compatibility, not behavior compatibility.
>> If we want to keep behavior compatibility, we must extend Vector J and allow
>> all modifications.
>>
>>
>>
>> So implementing a non-modifiable Collection/List may be the best. But
>> that’s only my opinion.
>>
>>
>>
>> -----
>>
>> Uwe Schindler
>>
>> H.-H.-Meier-Allee 63, D-28213 Bremen
>>
>> http://www.thetaphi.de
>>
>> eMail: uwe@thetaphi.de
>>
>>
>>
>> From: Shai Erera [mailto:serera@gmail.com]
>> Sent: Sunday, February 28, 2010 2:04 PM
>>
>> To: java-dev@lucene.apache.org
>> Subject: Re: SegmentInfos extends Vector
>>
>>
>>
>> Why do you say remove was unsupported before? I don't see it in the
>> class's impl. It just inherits from Vector and so remove is supported by
>> inheritance. Since the class is public, someone may have called it.
>>
>> Even if we change the class to impl List, period, we'll break back-compat,
>> just because of the synchronization Vector offers. If anyone out there
>> relies on that, it's a problem.
>>
>> On one hand, the best way would be is to impl Collection, as then someone
>> will be able to use Collections.synchronizedCollection if one needs it, or
>> call toArray etc. But Collection does not have a get(index) method, which
>> might be required and useful ...
>>
>> All in all, I don't feel like SegmentInfos is a true collection (even
>> though its Javadoc starts with "a collection ...". It adds lots of segments
>> related methods. The collection's ones are really get and iterator? So maybe
>> we should just impl Iterable and expose whatever API we feel is necessary?
>> Back-compat wise, if we change anything in this class's extension/implements
>> details, we break it.
>>
>> Unless the folks here don't think we should go to great lengths w/ this
>> class, and do whatever changes we dim are necessary, even at the cost of
>> breaking back-compat. And I'd vote that whether with this class or the new
>> one, we mark it as @lucene.internal.
>>
>> Shai
>>
>> On Sun, Feb 28, 2010 at 2:49 PM, Uwe Schindler <uwe@thetaphi.de> wrote:
>>
>> Hi Shai,
>>
>>
>>
>> I forgot to mention: Iterable is always a good idea. E.g. during my 3.0
>> generification, I made “BooleanQuery implements Iterable<BooleanClause>” and
>> so on. That makes look the code nice J. Also other classes got this
>> interface in Lucene. Also adding j.io.Closeable everywhere was a good idea.
>>
>>
>>
>> Uwe
>>
>>
>>
>> -----
>>
>> Uwe Schindler
>>
>> H.-H.-Meier-Allee 63, D-28213 Bremen
>>
>> http://www.thetaphi.de
>>
>> eMail: uwe@thetaphi.de
>>
>>
>>
>> From: Shai Erera [mailto:serera@gmail.com]
>> Sent: Sunday, February 28, 2010 1:38 PM
>>
>> To: java-dev@lucene.apache.org
>> Subject: Re: SegmentInfos extends Vector
>>
>>
>>
>> I would rather avoid implementing List .. we should implement Iterable for
>> sure, but I'd like to keep the API open either iterating in-order or getting
>> a particular SegmentInfo. Another thing, I haven't seen anywhere that remove
>> is called. In general I don't like to impl an interface just to throw UOE
>> everywhere ...
>>
>> I will open an issue. I usually investigate the code first before I open
>> an issue. Also, what about back-compat? Are we even allowed to change that
>> class? If not, then we can deprecate it and introduce a new one ...
>>
>> Shai
>>
>> On Sun, Feb 28, 2010 at 2:25 PM, Uwe Schindler <uwe@thetaphi.de> wrote:
>>
>> I think you should open an issue! I like this refactoring, maybe we can
>> still let it implement List<SegmentInfo> but only deprecated and most
>> methods should throw UOE. Just keep get() and so on.
>>
>>
>>
>> -----
>>
>> Uwe Schindler
>>
>> H.-H.-Meier-Allee 63, D-28213 Bremen
>>
>> http://www.thetaphi.de
>>
>> eMail: uwe@thetaphi.de
>>
>>
>>
>> From: Shai Erera [mailto:serera@gmail.com]
>> Sent: Sunday, February 28, 2010 1:20 PM
>>
>> To: java-dev@lucene.apache.org
>>
>> Subject: Re: SegmentInfos extends Vector
>>
>>
>>
>> Yes that's what I've been thinking as well - SegmentInfos should have a
>> segments-related API, not a List related. Whether the infos inside are kept
>> in a Map, List, Collection or array is an implementation detail. In fact, I
>> have a code which uses the API and could really benefit from a Map-like
>> interface, but perhaps other code needs things ordered (which is why we can
>> keep a TreeMap inside, or LinkedHahsMap). That's a great example to why it
>> should have its own API.
>>
>> The Lucene code usually calls SegmentInfos.info(int), but some places call
>> get(int) (which is inherited from Vector). That's bad.
>>
>> SegmentInfos is public, though it's tagged with @lucene.experimental. I
>> think it should be tagged with @lucene.internal as there's nothing
>> experimental about it?
>>
>> I don't mind doing the refactoring. Not sure how this will affect
>> back-compat (is it acceptable for this classs?). I've touched SegmentInfos
>> in LUCENE-2289, so I'll wait for someone to pick it up first, so that I
>> don't work on it in parallel.
>>
>> Thanks,
>> Shai
>>
>> On Sun, Feb 28, 2010 at 1:37 PM, Uwe Schindler <uwe@thetaphi.de> wrote:
>>
>> I think this is historically. I have seen this in my big 3.0
>> generification patches, too. But I did not wanted to change it as Vector has
>> other allocation schema than ArrayList. But maybe we should simply change
>> it, it’s a package-private class, right?
>>
>>
>>
>> But in general subclassing those implementations is not the best thing you
>> can do. In general the class should extend Object or something else and just
>> have final field of type List<…>. Exposing the whole API of List to the
>> outside is bad.
>>
>>
>>
>> +1 to refactor this class (and don’t let it extend a Collections class).
>>
>>
>>
>> -----
>>
>> Uwe Schindler
>>
>> H.-H.-Meier-Allee 63, D-28213 Bremen
>>
>> http://www.thetaphi.de
>>
>> eMail: uwe@thetaphi.de
>>
>>
>>
>> From: Shai Erera [mailto:serera@gmail.com]
>> Sent: Sunday, February 28, 2010 12:33 PM
>> To: java-dev@lucene.apache.org
>> Subject: SegmentInfos extends Vector
>>
>>
>>
>> Hi
>>
>> What's the reason SegmentInfos extends Vector rather than say ArrayList?
>> Do we need the synchronization around it which Vector provides?
>>
>> Shai
>>
>>
>>
>>
>>
>>
>>
>>
>

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