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https://issues.apache.org/jira/browse/SOLR-9506?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15521130#comment-15521130
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Pushkar Raste commented on SOLR-9506:
-------------------------------------

POC/Initial commit - 
https://github.com/praste/lucene-solr/commit/ca55daa9ea1eb23232173b50111b9068f1817c13

There are two issues we still need to solve. 
* How to compute `versionsInHash` from `versionsInHash` of individual segments. 
We can not use current `versionsHash` (unless we cache all the individual 
version numbers), as it is not additive.  Consider following scenario
*Leader segments, versions and hash*
*seg1* : 
 versions: 100, 101, 102  
  versionHash: hash(100) + hash(101) + hash(102)
*seg2*: 
 versions: 103, 104, 105
  versionHash: hash(103) + hash(104) + hash(105) 
\\ \\ *Replica segments, versions and hash*
*seg1*: 
 versions: 100, 101
  versionHash: hash(100) + hash(101) 
*seg2*: 
 versions: 102, 103, 104, 105
  versionHash: hash(102) + hash(103) + hash(104) + hash(105)
\\ \\Leader and Replica are essentially in sync, however using current method 
there is no way to compute and ensure cumulative `versionHash` of leader and 
replica would match

* I still need to figure out how to keep cache in   `DefaultSolrCoreState`, so 
that we can reuse `IndexFingerprint` of individual segments when a new Searcher 
is opened.  

> cache IndexFingerprint for each segment
> ---------------------------------------
>
>                 Key: SOLR-9506
>                 URL: https://issues.apache.org/jira/browse/SOLR-9506
>             Project: Solr
>          Issue Type: Improvement
>      Security Level: Public(Default Security Level. Issues are Public) 
>            Reporter: Noble Paul
>
> The IndexFingerprint is cached per index searcher. it is quite useless during 
> high throughput indexing. If the fingerprint is cached per segment it will 
> make it vastly more efficient to compute the fingerprint



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