Minor nit. For IndexUpgraderTool and optimize to be identical, you have to specify maxSegments=1 on optimize.
As of LUCENE-7976, optimize respects the max segment size and does _not_ necessarily rewrite segments that have no deleted documents, especially if they’re near 5G which is the default max segment size. Which nit doesn’t matter in this case of course… Best, Erick > On Apr 1, 2019, at 9:03 AM, Shawn Heisey <apa...@elyograg.org> wrote: > > On 4/1/2019 9:47 AM, Herbert Hackelsberger wrote: >> So, am I correct: >> - When using the IndexUpgrader, it will make the Index usable in the actual >> version, without all new features. >> - Using the Index Upgrader in the future again on the next major version >> will again result in this error situation. > > That is correct. > > If the "new features" are not related to the index format, then you will have > full access to them even with an older index. > > The Lucene IndexUpgrader function does a forceMerge on the index, down to one > segment. Solr calls that operation "optimize". > > There's really no need to use IndexUpgrader. Solr will directly use an index > from one major version back with no trouble. If you ask Solr to optimize the > index down to one segment, that is an identical operation to IndexUpgrader, > with the difference that you can still access the index while it is happening. > > Thanks, > Shawn
