warning: I'm no expert on other similarities. Having said that, I'm not aware of similarities being used in the indexing process - during indexing term frequency, document frequency, field norms, and so on are all recorded. These are things that the default similarity (TF/IDF) uses to calculate its score. So long as the data required by the similarity is already in the index, I don't see why changing similarity would require a re-index.
But then, who ever wrote that must have been thinking of something... Upayavira On Wed, Aug 19, 2015, at 05:40 PM, Tom Burton-West wrote: > Hello all, > > The last time I worked with changing Simlarities was with Solr 4.1 and at > that time, it was possible to simply change the schema to specify the use > of a different Similarity without re-indexing. This allowed me to > experiment with several different ranking algorithms without having to > re-index. > > Currently the documentation states that while doing this is > theoretically > possible but not well defined: > > "To change Similarity > <http://lucene.apache.org/core/5_2_0/core/org/apache/lucene/search/similarities/Similarity.html>, > one must do so for both indexing and searching, and the changes must > happen > before either of these actions take place. Although in theory there is > nothing stopping you from changing mid-stream, it just isn't well-defined > what is going to happen." > > http://lucene.apache.org/core/5_2_0/core/org/apache/lucene/search/similarities/package-summary.html#changingSimilarity > > Has something changed between 4.1 and 5.2 that actually will prevent > changing Similarity without re-indexing from working, or is this just a > warning in case at some future point someone contributes code so that a > particular similarity takes advantage of a different index format? > > Tom
