The IndexBasedSpellChecker builds a parallel index based on the Solr index and performs spellchecking using this parallel index. For this, a field needs to be defined as a basis for the index terms. The easiest way is to copy terms from some fields (subject, description, and so on) to another field created for spellchecking. Here is a simple example of the IndexBasedSpellChecker approach configured in solrconfig.xml:

<searchComponent name="spellcheck" class="solr.SpellCheckComponent">
 <lst name="spellchecker">
 <str name="classname">solr.IndexBasedSpellChecker</str>
 <str name="spellcheckIndexDir">./spellchecker</str>
 <str name="field">content</str>
 <str name="buildOnCommit">true</str>
 <!-- optional elements with defaults
 <str name="distanceMeasure">org.apache.lucene.search.spell.LevensteinDistance</str>
 <str name="accuracy">0.5</str>
 -->
 </lst>
</searchComponent>

The attribute classname defines the approach to be used for spellchecking. If we do not define this attribute, solr.IndexBasedSpellChecker is the default one used for spellchecking.