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From: Ian Lea <ian.lea@gmail.com>
Date: Tue, 21 Sep 2010 16:12:11 +0100
Message-ID: <AANLkTi=_tTpgomnmKYXj=iMtr-RzmRP4gqHMQdH8fdVf@mail.gmail.com>
Subject: Re: recommended way to identify a version to pass to StandardAnalyzer
 constructor?
To: java-user@lucene.apache.org
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+1 for a static method to get the appropriate value of Version.


--
Ian.


On Sun, Sep 19, 2010 at 11:21 PM, Bill Janssen <janssen@parc.com> wrote:
> Simon Willnauer <simon.willnauer@googlemail.com> wrote:
>
>> On Fri, Sep 17, 2010 at 11:45 PM, Bill Janssen <janssen@parc.com> wrote:
>> > Simon Willnauer <simon.willnauer@googlemail.com> wrote:
>> >
>> >> On Fri, Sep 17, 2010 at 8:14 PM, Bill Janssen <janssen@parc.com> wrot=
e:
>> >> > Simon Willnauer <simon.willnauer@googlemail.com> wrote:
>> >> >
>> >> >> Hey Bill,
>> >> >> let me clarify what Version is used for since I think that caused
>> >> >> little confusion.
>> >> >
>> >> > Thanks.
>> >> >
>> >> >> The Version constant was mainly introduced to help
>> >> >> users with backwards compatibility and upgrading their codebase to=
 a
>> >> >> new version of lucene without breaking existing applications / ind=
exes
>> >> >> build with previous versions. For instance StandardAnalyzer preser=
ves
>> >> >> the positionIncrement in its StopFilter which was introduces in Lu=
cene
>> >> >> 2.9. If you use 2.4 and upgrade to 2.9 this change might break you=
 app
>> >> >> since you indexed with a 2.4 behavior. You phrasequeries might not
>> >> >> work as expected anymore. If you don't have any upgrade issues or =
if
>> >> >> you can simply reindex you might just use the latest version.
>> >> >
>> >> > That's what I'm trying to do. =A0But how? =A0LUCENE_CURRENT is depr=
ecated!
>> >> >
>> >> > How about adding a constructor for StandardAnalyzer that takes no
>> >> > parameters and is implicitly LUCENE_CURRENT?
>> >>
>> >> We deprecated LUCENE_CURRENT for a good reason that is that folks wil=
l
>> >> run into big trouble if they upgrade from X to X+n because behavior
>> >> may change dramatically due to optimizations, bug fixes and useful
>> >> features. If you blindly pass LUCENE_CURRENT you might end up with
>> >> incompatible APIs in some cases (we do deploy "sophisticated backward=
s
>> >> layers" like we did in CharTokenizer) or query analysis which will no=
t
>> >> work with you existing Version X index.
>> >
>> > Yes, but that's not an issue if I don't *have* existing version X
>> > indices, which I don't.
>> Well then why don't you just use the Version.LUCENE_30 and assign it
>> to some static final variable like:
>> class MyConstants { public final Version LUCENE_VERSION =3D
>> Version.LUCENE_30; } and use it everywhere?!
>
> Because that will break if what my users have installed is Lucene 2.9.3.
>
>> We moved away from LUCENE_CURRENT for the reasons I mentioned - if
>> that made you aware of what could happen our plans worked out.
>
> I was already aware, but I do appreciate you folks thinking of your
> users. =A0I just wish those plans had been thought out a bit more. =A0But
> that's software development, isn't it :-?
>
>> Version of the code? I don't understand.. the max value of Version is
>> your lucene version, does that help?!
>
> Yep. =A0That's what I'm using:
>
> =A0 =A0# we'd like to make this the latest Version that this Lucene knows
> =A0 =A0# about, because that's what the index will be using, but using
> =A0 =A0# Version.LUCENE_CURRENT is deprecated, and there's no API to map
> =A0 =A0# from the Lucene version string to the Version value for that
> =A0 =A0# string. =A0To make things worse, the 2.9 code doesn't support th=
e
> =A0 =A0# values() method, and Version doesn't implement Comparable, so I
> =A0 =A0# can't just use max(). =A0So, this complexity:
>
> =A0 =A0def _order(v1, v2):
> =A0 =A0 =A0 =A0if v1.equals(v2):
> =A0 =A0 =A0 =A0 =A0 =A0return 0
> =A0 =A0 =A0 =A0if v1.onOrAfter(v2):
> =A0 =A0 =A0 =A0 =A0 =A0return 1
> =A0 =A0 =A0 =A0else:
> =A0 =A0 =A0 =A0 =A0 =A0return -1
> =A0 =A0_values =3D sorted([getattr(Version, x) for x in Version.__dict__
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (x.startswith("LUCENE") and=
 (x !=3D "LUCENE_CURRENT"))],
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 cmp=3D_order)
> =A0 =A0_indexversion =3D _values[-1]
> =A0 =A0del _order, _values
>
>
>> > Or, is there a method which will take a Lucene version, expressed as a
>> > Package or perhaps even a string like "3.0.2", and return the
>> > appropriate Version value? =A0If so, I could write my own code to retr=
ieve
>> > the Lucene version, then call that method to retrieve the Version valu=
e.
>>
>> org.apache.lucene.util.Constants#LUCENE_MAIN_VERSION
>> org.apache.lucene.util.Constants#LUCENE_VERSION
>
> Yes, those are the strings I would use. =A0Now, how do I map from that
> string to an appropriate value of Version? =A0I think Version should grow
> a static method for doing that:
>
> =A0Version theVersion =3D Version.valueOf(Constants.LUCENE_MAIN_VERSION);
>
> Thanks,
>
> Bill
>
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