Shawn, my impression is that you WILL be able to upgrade a 5.x index to 6.x and then to 7.x for use with 7.x. So your wiki page is a bit too strict here. But if you ever want to upgrade to 8.x, that version will require the "first created" version to be 7.0 or later, so you'll need a full reindex. See SOLR-12281 <https://issues.apache.org/jira/browse/SOLR-12281>.
I'd also recommend to plan for a full re-index, and also upgrade to new field types etc at the same time. Feel free to give this tool https://github.com/cominvent/solr-tools/tree/master/upgradeindex <https://github.com/cominvent/solr-tools/tree/master/upgradeindex> a spin in your test environtment and then just test whether 7.5 works on that index :) -- Jan Høydahl, search solution architect Cominvent AS - www.cominvent.com > 5. okt. 2018 kl. 16:49 skrev Shawn Heisey <apa...@elyograg.org>: > > On 10/5/2018 4:41 AM, padmanabhan1616 wrote: >> 1. We cannot upgrade directly from 5.x to 7.x instead upgrade to 5.5 then >> upgrade to 7 as there is major index format level changes taken place in 5.5 >> or later version. > > Solr 7.x cannot read indexes from 5.5. It can only read indexes that were > *fully* constructed by versions back to 6.0.0. > >> 1. Use index upgrade tool which can allow to upgrade all old indexes to new >> index format then we can upgrade to 7.x version easily. > > We have been advised by Lucene experts that if a version that's at least two > major versions before the target version has *EVER* touched the index, > there's no guarantee that the index will work even after upgrading through > the major versions one by one. The compatibility guarantee only goes back one > major version. > > I would strongly recommend with ANY upgrade that you always build the index > from scratch. That produces the best results. > > This is becoming a frequently asked question, so I have built a wiki page to > answer it: > > https://wiki.apache.org/solr/VersionCompatibility > > Thanks, > Shawn >
