This filter uses regular expressions to replace or change character patterns.

Arguments:

• pattern: The regular expression pattern to apply to the incoming text
• replacement: The text to use to replace matching patterns

Example:

<fieldType name="text_en" class="solr.TextField" positionIncrementGap="100">
 <analyzer>
 <charFilter class="solr.PatternReplaceCharFilterFactory" pattern="(w+)(ing)" replacement="$1"/>
 <tokenizer class="solr.WhitespaceTokenizerFactory"/>
 </analyzer>
 </fieldType>

Input: showing see-ing viewing

Output: show, see-ing, view

As per the behavior of the pattern, ing is removed from the end of the words except see-ing.

Explaining every char filter is not possible here. Please refer to the Solr documents for these.