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https://issues.apache.org/jira/browse/LUCENE-3082?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13030518#comment-13030518
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Shai Erera commented on LUCENE-3082:
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This is a great idea. We should also allow one to plug in a
PayloadProcessorProvider so he can rewrite the payload "on the go" if need be.
Also, while the index is being upgraded, I think it will be useful if we merge
the segments that are upgraded, however not do cascading merges. Since segments
are rewritten anyway, we can only gain from the merge. As always, if not
everybody agree on this, we can make it a parameter.
And let's make sure that whatever 'upgrade' means is at the application
control. I.e., upgrade can be simply upgrading from 3x to 4.0, but it can also
be using PayloadProcessorProvider as well suddenly deciding that all segments
should be compound. I'm pretty sure I'll want to control the first two, not so
about the last one.
It can be a simple 'boolean shouldUpgradeSegment(SegmentInfo)' on this
UpgradeMP, which apps can override.
> Add index upgrade method to IndexWriter to force an upgrade of all segments
> to last recent supported index format without optimizing
> ------------------------------------------------------------------------------------------------------------------------------------
>
> Key: LUCENE-3082
> URL: https://issues.apache.org/jira/browse/LUCENE-3082
> Project: Lucene - Java
> Issue Type: New Feature
> Components: Index
> Reporter: Uwe Schindler
> Priority: Minor
> Fix For: 3.2, 4.0
>
>
> Currently if you want to upgrade an old index to the format of your current
> Lucene version, you have to optimize your index or use
> addIndexes(IndexReader...) [see LUCENE-2893] to copy to a new directory. The
> optimize() approach fails if your index is already optimized.
> I propose to add a method to IndexWriter thats similar to optimize(), that
> uses a custom MergePolicy to upgrade all segments to the last format. This
> MergePolicy could simply also ignore all segments already up-to-date. All
> segments in prior formats would be merged to a new segment. The tool could
> optionally also optimize the index.
> This issue is different from LUCENE-2893, as it would only support upgrading
> indexes from previous Lucene versions in-place using the official path. Its a
> tool for the end user, not a developer tool.
> This addition should also go to Lucene 3.x, as we need to make users with
> pre-3.0 indexes go the step through 3.x, else they would not be able to open
> their index with 4.0. With this tool in 3.x the users could safely upgrade
> their index without relying on optimize to work on already-optimized indexes.
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