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From Apache Wiki <wikidi...@apache.org>
Subject [Solr Wiki] Trivial Update of "SolrFacetingOverview" by jeffnewburn
Date Thu, 18 Jun 2009 16:53:10 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Solr Wiki" for change notification.

The following page has been changed by jeffnewburn:
http://wiki.apache.org/solr/SolrFacetingOverview

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      * '''Enum Based Field Queries''':  If {{{facet.method=enum}}} or the field is defined
in the schema as boolean, then Solr will iterate over all of the indexed terms for the field,
and for each term it will get a filter from the filterCache and calculate the intersection
with the filter for the base query.  This is excellent for fields where there is a small set
of distinct values.  The average number of values per document does not matter.  For example,
faceting on a field with U.S. States e.g. `Alabama, Alaska, ... Wyoming` would lead to fifty
cached filters which would be used over and over again. The [:SolrCaching#filterCache:filterCache]
should be large enough to hold all of the cached filters.
  
-     * '''Field Cache''': If {{{facet.method=fc}}} then a field-cache approach will be used.
 This is currently implemented using either the the Lucene [http://lucene.apache.org/java/docs/api/org/apache/lucene/search/FieldCache.html
FieldCache] or (starting in Solr 1.4) an !UnInvertedField if the field is multivalued or tokenized.
 Each document is looked up in the cache to wee what terms/values it contains, and a tally
is incremented for each value.  This is excellent for situations where the number of indexed
values for the field is high, but the number of values per document is low.  For multi-valued
fields, a hybrid approach is used that uses term filters from the filterCache for terms that
match many documents.
+     * '''Field Cache''': If {{{facet.method=fc}}} then a field-cache approach will be used.
 This is currently implemented using either the the Lucene [http://lucene.apache.org/java/docs/api/org/apache/lucene/search/FieldCache.html
FieldCache] or (starting in Solr 1.4) an !UnInvertedField if the field is multivalued or tokenized.
 Each document is looked up in the cache to see what terms/values it contains, and a tally
is incremented for each value.  This is excellent for situations where the number of indexed
values for the field is high, but the number of values per document is low.  For multi-valued
fields, a hybrid approach is used that uses term filters from the filterCache for terms that
match many documents.
  

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