The IndexUpgraderTool does a forceMerge(1). If you have a large index, that has its own problems, but will work. The threshold for the issues is 5G. See: https://lucidworks.com/post/solr-and-optimizing-your-index-take-ii/ I should emphasize that if you have a very large single segment as a result, it’ll eventually shrink if it accumulated deleted (or updated) documents, it’ll just require a bunch of I/O amortized over time.
IndexUpgraderTool will _not_ allow you to take an index originally created with 7x to be used in 9x. (Uwe, I’ve been telling people this for a long time, if I’ve been lying please let me know!). Starting with Lucene 6, a version is written into each segment. Upon merge, the lowest version stamp is preserved. Lucene will refuse to open an index where _any_ segment has a version stamp X-2 or older. Best, Erick > On Nov 20, 2020, at 7:57 AM, Michael Sokolov <msoko...@gmail.com> wrote: > > I think running the upgrade tool would also be necessary to set you up for > the next upgrade, when 9.0 comes along. > > On Fri, Nov 20, 2020, 4:25 AM Uwe Schindler <u...@thetaphi.de> wrote: > >> Hi, >> >>> Currently I am using Lucene 7.3, I want to upgrade to lucene 8.5.1. >> Should >>> I do reindexing in this case ? >> >> No, you don't need that. >> >>> Can I make use of backward codec jar without a reindex? >> >> Yes, just add the JAR file to your classpath and it can read the indexes. >> Updates written to the index will use the new codecs. To force a full >> upgrade (rewrite all segments), invoke the IndexUpgrader class either from >> your code or using the command line. But this is not needed, it just makes >> sure that you can get rid of the backwards-codecs jar. >> >> Uwe >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org >> For additional commands, e-mail: java-user-h...@lucene.apache.org >> >> --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
