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Posted to issues@lucene.apache.org by "ASF subversion and git services (Jira)" <ji...@apache.org> on 2021/01/19 08:25:00 UTC
[jira] [Commented] (LUCENE-9669) N-2 compatibility for file formats
[ https://issues.apache.org/jira/browse/LUCENE-9669?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17267738#comment-17267738 ]
ASF subversion and git services commented on LUCENE-9669:
---------------------------------------------------------
Commit c1ae6dc07c9a988533cbe7176bdeb49e2fca1d9c in lucene-solr's branch refs/heads/master from Simon Willnauer
[ https://gitbox.apache.org/repos/asf?p=lucene-solr.git;h=c1ae6dc ]
LUCENE-9669: Add an expert API to allow opening indices created < N-1 (#2212)
Today we force indices that were created with N-2 and older versions of Lucene
to fail on open. This check doesn't even check if the codecs are available. In order
to allow users to open older indices and for us to support N-2 versions this change
adds an API on DirectoryReader to specify a minimum index version on a per reader basis.
This doesn't apply for the IndexWriter which will fail on opening older indices.
> N-2 compatibility for file formats
> ----------------------------------
>
> Key: LUCENE-9669
> URL: https://issues.apache.org/jira/browse/LUCENE-9669
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Simon Willnauer
> Assignee: Simon Willnauer
> Priority: Major
> Fix For: master (9.0)
>
> Time Spent: 3h 10m
> Remaining Estimate: 0h
>
> Currently Lucene supports reading and writing indices that have been
> created with the current or previous (N-1) version of Lucene. Lucene
> refuses to open an index created by N-2 or earlier versions.
> I would like to propose that Lucene adds support for opening indices
> created by version N-2 in read-only mode. Here's what I have in mind:
> - Read-only support. You can open a reader on an index created by
> version N-2, but you cannot open an IndexWriter on it, meaning that
> you can neither delete, update, add documents or force-merge N-2
> indices.
> - File-format compatibility only. File-format compatibility enables
> reading the content of old indices, but not more. Everything that is
> done on top of file formats like analysis or the encoding of length
> normalization factors is not guaranteed and only supported on a
> best-effort basis.
> The reason I came up with these limitations is because I wanted to
> make the scope minimal in order to retain Lucene's ability to move
> forward. If there is consensus to move forward with this, I would like
> to target Lucene 9.0 with this change.
> This is a follow-up of the mailinglist thread [here|http://mail-archives.apache.org/mod_mbox/lucene-dev/202101.mbox/%3CCAAHmpkg1BD9RtmVFR4jweYgYAXwz5OsY1hV9ubZkS0fHSFnTCQ@mail.gmail.com%3E]
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