Token Chars Mapping to Ngram Filter ElasticSearch NEST

Question

I\'m trying to replicate the below mappings using NEST and facing an issue while mapping the token chars to the tokenizer.

{
   \"settings\": {
      \"analy         


        

Answer 1

NGram Tokenizer supports token characters (token_chars), using these to determine which characters should be kept in tokens and split on anything that isn't represented in the list.

NGram Token Filter on the other hand operates on the tokens produced by a tokenizer, so only has options for the min and max grams that should be produced.

Based on your current analysis chain, it's likely you want something like the following

var createIndexResponse = client.CreateIndex(defaultIndex, c => c
    .Settings(st => st
        .Analysis(an => an
            .Analyzers(anz => anz
                .Custom("ngram_analyzer", cc => cc
                    .Tokenizer("ngram_tokenizer")
                    .Filters(nGramFilters))
                )
            .Tokenizers(tz => tz
                .NGram("ngram_tokenizer", td => td
                    .MinGram(2)
                    .MaxGram(20)
                    .TokenChars(
                        TokenChar.Letter,
                        TokenChar.Digit,
                        TokenChar.Punctuation,
                        TokenChar.Symbol
                    )
                )          
            )
        )
    )
);