parveensaini opened a new pull request, #15586:
URL: https://github.com/apache/lucene/pull/15586
### **Description**
This PR adds a concise documentation note clarifying that scoring and
ranking behavior can legitimately change across major Lucene versions, even
when no index format break occurs.
**Motivation**
While upgrading a production Solr deployment across multiple Lucene major
versions, we encountered ranking differences that were not attributable to
index corruption or misconfiguration. Investigation showed these differences
stemmed from intentional changes accumulated over major releases (similarity
defaults, normalization details, tokenization/scoring refinements, etc.).
Although these changes are expected and documented in individual release
notes, it is not always obvious to users performing large version jumps that
*preserving historical ranking behavior may require explicitly pinning or
supplying a custom `Similarity`*.
**What this PR adds**
* A short, centralized note highlighting:
* Scoring is not guaranteed to be stable across major versions
* Large version jumps can surface accumulated scoring differences
* Custom `Similarity` implementations are the appropriate mitigation if
strict backward ranking compatibility is required
* No behavior or API changes
**Why documentation (not code)**
The underlying behavior is intentional and consistent with Lucene’s
evolution model. This PR aims to reduce confusion during major upgrades by
making the tradeoff explicit and discoverable.
**Scope**
* Documentation-only change
* No impact on runtime behavior
* Intended to complement existing `CHANGES.txt` and migration guidance
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