+1 -- Lucene should not _prevent_ this. I forget where things stood in the past conversations about this subject... I think most recently raised by Erick Ericson. I recall that we don't want to maintain the code to read older indices... which I sympathize with... but I recall there is code that actively *blocks* you (end user) from reading N-2 which I think goes too far, _forcing_ you to fork Lucene to work around that. At least a user should be able to maintain however far back if they have their own codecs that they maintain (as I do at work).
~ David Smiley Apache Lucene/Solr Search Developer http://www.linkedin.com/in/davidwsmiley On Wed, Jan 6, 2021 at 8:48 AM Ishan Chattopadhyaya < [email protected]> wrote: > Sounds great, +1 > > On Wed, Jan 6, 2021 at 3:10 PM Simon Willnauer <[email protected]> > wrote: > >> Hello all, >> >> 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. >> >> Simon >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [email protected] >> For additional commands, e-mail: [email protected] >> >>
