Apache Solr Reference Guide Covering Apache Solr 6.0

The default language can also be set using Carrot2-specific algorithm attributes (in this case the MultilingualClust
ering.defaultLanguage attribute).
Tweaking Algorithm Settings
The algorithms that come with Solr are using their default settings which may be inadequate for all data sets. All
algorithms have lexical resources and resources (stop words, stemmers, parameters) that may require tweaking
to get better clusters (and cluster labels). For Carrot2-based algorithms it is probably best to refer to a dedicated
tuning application called Carrot2 Workbench (screenshot below). From this application one can export a set of
algorithm attributes as an XML file, which can be then placed under the location pointed to by carrot.resourc
esDir.
Providing Defaults
The default attributes for all engines (algorithms) declared in the clustering component are placed under carrot
.resourcesDir and with an expected file name of engineName-attributes.xml. So for an engine named
lingo and the default value of carrot.resourcesDir, the attributes would be read from a file in conf/clus
tering/carrot2/lingo-attributes.xml.
An example XML file changing the default language of documents to Polish is shown below.
attributes
Tweaking at Query-Time
The clustering component and Carrot2 clustering algorithms can accept query-time attribute overrides. Note that
certain things (for example lexical resources) can only be initialized once (at startup, via the XML configuration
files).
An example query that changes the LingoClusteringAlgorithm.desiredClusterCountBase parameter
for the Lingo algorithm: http://localhost:8983/solr/techproducts/clustering?q=*:*&rows=100&LingoClusteringAlgor
ithm.desiredClusterCountBase=20.
The clustering engine (the algorithm declared in solrconfig.xml) can also be changed at runtime by passing
clustering.engine=name request attribute: http://localhost:8983/solr/techproducts/clustering?q=*:*&rows=10
0&clustering.engine=kmeans
Performance Considerations
Dynamic clustering of search results comes with two major performance penalties:
Increased cost of fetching a larger-than-usual number of search results (50, 100 or more documents),
Additional computational cost of the clustering itself.
Apache Solr Reference Guide 6.0
369