Hi all, Following up on the earlier thread about the migration validation approach for major Solr upgrades, I wrote up the full story and lessons learned from the Solr 5 to 8 migration we discussed.
Sharing here in case it’s useful for others planning similar upgrades: https://dzone.com/articles/solr5-to-solr8-migration-ads-system Best, Parveen On Sat, Feb 28, 2026 at 9:17 AM Parveen Saini <[email protected]> wrote: > Hi all, > > While migrating a production system from Solr 5 to 8, we encountered > subtle ranking drift that did not surface in standard upgrade testing. The > system functioned correctly, but ranking behavior changed in non obvious > ways. We observed score distribution shifts, candidate set differences > influenced by negative score handling, and p99 latency regressions. > > Using that migration as a real world case, I put together a small side by > side validation harness designed to make behavioral differences across > major Solr versions observable. The goal is not to provide version specific > guidance, but to offer a structured approach for detecting ranking and > performance drift during major upgrades. > > The harness compares docset overlap, score distributions, and query level > behavior across versions. > > Sharing in case it is useful for others planning major Solr upgrades: > https://github.com/parveensaini/solr-lucene-migration-correctness > > Happy to share more details or present the approach at an upcoming > community meetup if there is interest. > > Thanks, > Parveen >
