[[analysis-pattern-replace-charfilter]]
=== Pattern Replace Char Filter

The `pattern_replace` char filter allows the use of a regex to
manipulate the characters in a string before analysis. The regular
expression is defined using the `pattern` parameter, and the replacement
string can be provided using the `replacement` parameter (supporting
referencing the original text, as explained
http://docs.oracle.com/javase/6/docs/api/java/util/regex/Matcher.html#appendReplacement(java.lang.StringBuffer,%20java.lang.String)[here]).
For more information check the
http://lucene.apache.org/core/4_3_1/analyzers-common/org/apache/lucene/analysis/pattern/PatternReplaceCharFilter.html[lucene
documentation]

Here is a sample configuration:

[source,js]
--------------------------------------------------
{
    "index" : {
        "analysis" : {
            "char_filter" : {
                "my_pattern":{
                    "type":"pattern_replace",
                    "pattern":"sample(.*)",
                    "replacement":"replacedSample $1"
                }
            },
            "analyzer" : {
                "custom_with_char_filter" : {
                    "tokenizer" : "standard",
                    "char_filter" : ["my_pattern"]
                },
            }
        }
    }
}
--------------------------------------------------