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From Simon Willnauer <simon.willna...@googlemail.com>
Subject Re: recommended way to identify a version to pass to StandardAnalyzer constructor?
Date Sat, 18 Sep 2010 12:04:17 GMT
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> wrote:
>> > 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 / indexes
>> >> build with previous versions. For instance StandardAnalyzer preserves
>> >> the positionIncrement in its StopFilter which was introduces in Lucene
>> >> 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.  But how?  LUCENE_CURRENT is deprecated!
>> >
>> > 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 will
>> 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 backwards
>> layers" like we did in CharTokenizer) or query analysis which will not
>> 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 =
Version.LUCENE_30; } and use it everywhere?!

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
rather answer some questions on the list regarding version than have
tons of people with broken applications.

>
>> What you should do is pick YOUR latest version manually and go through
>> the changes once you upgrade. Write unittests for you API to make sure
>> it does not break you code. Its worth the trouble!
>
> Simon, this advice isn't helping.

sorry, I though I would explain it in detail and you could find the
best way for your application - didn't work out ey?!
>
> I have unittests, and, yes, they are worth the trouble.  I always
> re-index my collection if I change to a different version of Lucene.
> So I'd like to make my choice of the value of
> org.apache.lucene.util.Version automatically, using tools, instead of
> choosing it manually, based on what version of Lucene the user has
> installed, and without encoding a limited set of strings in my
> application.

see above
>
> How do I do that?  More directly, is there any attribute or static
> method somewhere in Lucene which will return a value of
> org.apache.lucene.util.Version that corresponds to the version of the
> code?  That's what I'm looking for.  Version.LUCENE_CURRENT looks good,
> but it's deprecated.
Version of the code? I don't understand.. the max value of Version is
your lucene version, does that help?!
>
> 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?  If so, I could write my own code to retrieve
> the Lucene version, then call that method to retrieve the Version value.

org.apache.lucene.util.Constants#LUCENE_MAIN_VERSION
org.apache.lucene.util.Constants#LUCENE_VERSION

simon
>
> Bill
>
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