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From 郑文兴 <zhen...@csdn.net>
Subject RE: Any compatiblity issue in the upgrade from Lucene Core 3.2.0 to Core 6.1.0?
Date Tue, 09 Aug 2016 02:36:25 GMT
Then it sounds like that "re-index all the sources in 6.x" is the most feasible way, :(. 

-----Original Message-----
From: Trejkaz [mailto:trejkaz@trypticon.org] 
Sent: Tuesday, August 09, 2016 10:32 AM
To: Lucene Users Mailing List
Subject: Re: Any compatiblity issue in the upgrade from Lucene Core 3.2.0 to Core 6.1.0?

On Mon, Aug 8, 2016 at 1:37 PM, Erick Erickson <erickerickson@gmail.com> wrote:
> Yes. Lucene only guarantees back-compatibility with indexes for one 
> major version. That is, a 4.x release can read a 3.x Lucene index. But 
> a 5.x will not read a 3.x.
>
> So you have some options here:
> 1> re-index all your source in 6.x. This is probably easiest....
> 2> upgrade in stages, check out the IndexUpgradeTool.
> Here's the doc for 4.x, which should the 3.x version.
>
> I'll leave it to the people who know Lucene better than me to opine 
> about whether running the IndexUpgrader several times in succession 
> works well.

One problem is that IndexUpgrader and the rest of Lucene has the same package name in all
the subsequent versions. So there is a fiddly bit of renaming the packages in order to get
it all into one classpath.
Actually figuring out how to call the upgrader each time was also a bit interesting, given
that by renaming the packages, the Directory class had to be adapted in interesting ways to
eventually call through to the current Lucene's version of the Directory class. I think the
InfoStream had some interesting adapting challenges as well.

But even then... I'm not sure IndexUpgrader is 100% flawless. We had one issue initially where
it wasn't upgrading empty indexes at all, which I think is fixed now. More recently I think
we have hit a case where a failure occurred due to the index being corrupt, but the upgrade
method returned as if it was completely successful... almost like it was doing the merges
in the background, but not waiting until they complete.

TX

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