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Posted to dev@lucene.apache.org by GitBox <gi...@apache.org> on 2019/08/08 12:04:49 UTC
[GitHub] [lucene-solr] ErickErickson commented on issue #824: LUCENE-8755:
QuadPrefixTree robustness
ErickErickson commented on issue #824: LUCENE-8755: QuadPrefixTree robustness
URL: https://github.com/apache/lucene-solr/pull/824#issuecomment-519489983
No, IndexUpgraderTool doesn’t really help. It rewrites the index in the current format, but does not (and cannot) make it look just as though the index had been indexed from scratch. From Robert Muir:
“I think the key issue here is Lucene is an index not a database. Because it is a lossy index and does not retain all of the user's data, its not possible to safely migrate some things automagically. In the norms case IndexWriter needs to re-analyze the text ("re-index") and compute stats to get back the value, so it can be re-encoded. The function is y = f(x) and if x is not available its not possible, so lucene can't do it.”
So Lucene will work with X-1, but not version X-2. As of 8.0, it will refuse to even open an index that has ever been touched by Solr 6x or earlier, regardless of running IndexUpgraderTool etc.
Best,
Erick
> On Aug 8, 2019, at 12:55 AM, 鹿の遠音 <no...@github.com> wrote:
>
> I find that Lucene has a tool called IndexUpgrader. Maybe updating index is a better solution for backward compatibility?
>
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