[GitHub] [solr] alessandrobenedetti commented on a diff in pull request #872: SOLR-16204: Update lucene dependency version to 9.1.0

[GitBox <gi...@apache.org>]

alessandrobenedetti commented on code in PR #872:
URL: https://github.com/apache/solr/pull/872#discussion_r879175946


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solr/solr-ref-guide/modules/query-guide/pages/dense-vector-search.adoc:
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@@ -109,20 +109,20 @@ and the hyper-parameter of the HNSW algorithm make sure you set this configurati
 Here's how `DenseVectorField` can be configured with the advanced codec hyper-parameters:
 
 [source,xml]
-<fieldType name="knn_vector" class="solr.DenseVectorField" vectorDimension="4" similarityFunction="cosine" codecFormat="Lucene90HnswVectorsFormat" hnswMaxConnections="10" hnswBeamWidth="40"/>
+<fieldType name="knn_vector" class="solr.DenseVectorField" vectorDimension="4" similarityFunction="cosine" codecFormat="Lucene91HnswVectorsFormat" hnswMaxConnections="10" hnswBeamWidth="40"/>
 <field name="vector" type="knn_vector" indexed="true" stored="true"/>
 
 `codecFormat`::
 +
 [%autowidth,frame=none]
 |===
-|Optional |Default: `Lucene90HnswVectorsFormat`
+|Optional |Default: `Lucene91HnswVectorsFormat`
 |===
 +
 (advanced) Specifies the knn codec implementation to use
 +
 
-Accepted values: `Lucene90HnswVectorsFormat`.
+Accepted values: `Lucene91HnswVectorsFormat`.

Review Comment:
   The experimental Dense Vector Search under development in Lucene (and Solr consequentially) is expected to change a lot in this phase.
   There have been many changes both in Lucene 9.1.0 and in the upcoming 9.2.0.
   
   Some of these changes are backed by a new codec effectively, so it's a delicate balance.
   
   When features are marked as "Experimental" is it acceptable to make it simple and just require people to re-index(of course only if they use a vector-based field)?
   
   That codec param is going away soon anyway(we'll submit a PR after this for that), as it's preferable to give the user the ability to just choose the algorithm (currently only HNSW supported) rather than the internal codec.
   
   @msokolov , @mocobeta  what do you think?
   Thanks @madrob  for raising this, it's definitely something we need to discuss!



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