[jira] [Commented] (LUCENE-5956) Add runnable index upgrader

["Trejkaz (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-5956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14614606#comment-14614606 ] 

Trejkaz commented on LUCENE-5956:
---------------------------------

> how valuable is it to support older than N-1 indexes, when the analysis chains used to create them have now
> changed?

I'm currently writing a library to migrate from version 2 to 5. For most active indices it will be from 3 to 5. Which is to say, 100% of our existing users are on N-2. Nobody is using N-1 because we never released a supported version using that version. I'm sure there will be other companies in the same position.

Maintaining backwards compatibility for analysis is certainly possible and we're doing it. It's more work, particularly when the analysis API makes big changes, but as far as I know, we don't have the option to reindex because people complain about reindexing when their initial index took a month to create in the first place.

> how will SPI etc work here, will the older versions somehow have their own SPI lists in different classloader or
> something?

What I'm trying to do, which *should* work, and *appears* to be working, is to rename all org.apache.lucene for a given version to some.other.place.luceneN. At the moment, at least classname lookups appear to be working. (Other weird things are going on, but I don't have the foggiest idea what's going on there yet.)


> Add runnable index upgrader
> ---------------------------
>
>                 Key: LUCENE-5956
>                 URL: https://issues.apache.org/jira/browse/LUCENE-5956
>             Project: Lucene - Core
>          Issue Type: New Feature
>            Reporter: Ryan Ernst
>
> As a spinoff from discussion in LUCENE-5940, I'd like to add a new module "lucene-upgrader", move {{IndexUpgrader}} to this, and add embed older versions of lucene (just enough to upgrade indexes) in the built version of the module's jar.  This would be runnable from the command line with something like:
> {{java -jar lucene-upgrader-4.11.0.jar /path/to/index}}



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