Hi there, I'm using solr 9.1 to implement dense vector search using the documentation at https://solr.apache.org/guide/solr/latest/query-guide/dense-vector-search.html
According to the guide, a valid fieldType configuration is: <fieldType name="knn_vector" class="solr.DenseVectorField" vectorDimension="4" similarityFunction="cosine"/> Using the schema API, I added the following configuration: $ grep knn_vector managed-schema.xml <fieldType name="knn_vector" class="solr.DenseVectorField" vectorDimension="4" similarityFunction="euclidean"/> <field name="vector" type="knn_vector" multiValued="false" stored="true"/> However, when I try to submit a document containing a vector to the server, an error occurs: (truncated traceback): 2022-12-13 19:10:08.763 ERROR (qtp3540494-54) [ x:fsnn] o.a.s.s.HttpSolrCall org.apache.solr.common.SolrException: null KNN algorithm is not supported => org.apache.solr.common.SolrException: null KNN algorithm is not supported at org.apache.solr.core.SchemaCodecFactory$1.getKnnVectorsFormatForField(SchemaCodecFactory.java:134) org.apache.solr.common.SolrException: null KNN algorithm is not supported at org.apache.solr.core.SchemaCodecFactory$1.getKnnVectorsFormatForField(SchemaCodecFactory.java:134) ~[?:?] at org.apache.lucene.codecs.lucene92.Lucene92Codec$3.getKnnVectorsFormatForField(Lucene92Codec.java:101) ~[?:?] at org.apache.lucene.codecs.perfield.PerFieldKnnVectorsFormat$FieldsWriter.getInstance(PerFieldKnnVectorsFormat.java:148) ~[?:?] at org.apache.lucene.codecs.perfield.PerFieldKnnVectorsFormat$FieldsWriter.writeField(PerFieldKnnVectorsFormat.java:107) ~[?:?] at org.apache.lucene.index.VectorValuesWriter.flush(VectorValuesWriter.java:145) ~[?:?] at org.apache.lucene.index.IndexingChain.writeVectors(IndexingChain.java:461) ~[?:?] After having a dig through the source, I found https://github.com/apache/solr/pull/910 which added this check. I note that the documentation about dense vector search does describe the knnAlgorithm parameter, but says that it is optional with a default value of "hnsw". It seems that the patch changed the behaviour of this check to raise an error if the knnAlgorithm is null/missing, rather than only if the value isn't the expected "hnsw". If I update the fieldType in the schema to include the knnAlgorithm, hnswMaxConnections, and hnswBeamWidth parameters then I am able to successfully index and search on this field. Does this appear to be a bug in the code? Or if the parameter is expected to always be set, perhaps a bug in the documentation. Thanks, Alastair
