[[analysis-stemmer-override-tokenfilter]]
=== Stemmer Override Token Filter

Overrides stemming algorithms, by applying a custom mapping, then
protecting these terms from being modified by stemmers. Must be placed
before any stemming filters.

Rules are separated by `=>`

[cols="<,<",options="header",]
|=======================================================================
|Setting |Description
|`rules` |A list of mapping rules to use.

|`rules_path` |A path (either relative to `config` location, or
absolute) to a list of mappings.
|=======================================================================

Here is an example:

[source,js]
--------------------------------------------------
index :
    analysis :
        analyzer :
            myAnalyzer :
                type : custom
                tokenizer : standard
                filter : [lowercase, custom_stems, porter_stem]    
        filter:
            custom_stems:
                type: stemmer_override
                rules_path : analysis/custom_stems.txt
--------------------------------------------------
