Re: Standalone Solr upgrade from 4.x to 8.x

["Natarajan, Rajeswari" <ra...@sap.com.INVALID>]

Thanks much for the reply.

On 2/15/23, 4:12 PM, "Shawn Heisey" <apache@elyograg.org <ma...@elyograg.org>> wrote:


On 2/14/23 20:02, Natarajan, Rajeswari wrote:
> Would like to know if it is possible to upgrade standalone solr from 4.x to 8.x
> 
> Is there a wiki available. Please let me know.


In most cases when jumping more than one major version you will have to 
completely reindex from scratch.


You can't upgrade it step-by-step to one major version at a time, 
because starting in one of the 6.x versions, the Lucene version that 
originally wrote each segment is recorded and never gets updated or 
removed. If a segment has no version or the earliest version recorded 
is less than 7.0, then 8.x will refuse to open it. 9.x is similar for 
anything older than 8.0.


I have seen a tool that bypasses this version check, allowing upgrades 
that Lucene prevents. Even if you did use that tool and managed to get 
it to work, it's a bad idea, which is why it's explicitly blocked.


Thanks,
Shawn