How to add settings property with array value to ES-index using Nest

Question

"I'm trying to create in index for auto complete seach using ElasticSearch and its NEST .NET client. I'm following the tutorial on http://qbox.io/blog/an-introduction-to-ngrams-in-elasticsearch and have run into problems when creating the index and its settings. Sepcifically I would like to create the index with the following settings (taken straight out of the tutorial's TL;DR, to begin with):

PUT /test_index
{
  "settings": {
    "analysis": {
      "filter": {
        "edge_ngram_filter": {
           "type": "edge_ngram",
           "min_gram": 2,
           "max_gram": 20
        }
     },
     "analyzer": {
        "edge_ngram_analyzer": {
           "type": "custom",
           "tokenizer": "standard",
           "filter": [
              "lowercase",
              "edge_ngram_filter"
           ]
        }
     }
  }
}

My problem is that I don't know how to send the "filter": [ "lowercase", "edge_ngram_filter" ] part using NEST. My current attempt looks like this:

esclient.CreateIndex("test_index", s => s
    .Settings(settings => settings
        .Add("analysis.filter.edge_ngram_filter.type", "edge_ngram")
        .Add("analysis.filter.edge_ngram_filter.min_gram", "2")
        .Add("analysis.filter.edge_ngram_filter.max_gram", "20")
        .Add("analysis.analyzer.edge_ngram_analyzer.type", "custom")
        .Add("analysis.analyzer.edge_ngram_analyzer.tokenizer", "standard")
        // Interesting part on the line below!
        .Add("analysis.analyzer.edge_ngram_analyzer.filter", new string[] { "lowercase", "edge_ngram_filter" })
    )
);

but this fail withe a JsonWriterException: "Unsupported type: System.String[]. Use the JsonSerializer class to get the object's JSON representation. Path 'settings.index'.". I have tried to simply provide the JSON array manually ( .Add("analysis.analyzer.edge_ngram_analyzer.filter", "[ \\"lowercase\\", "\\edge_ngram_analyzer\\" ]") ) the JSON is instead escaped as a string.

Does the NEST API provide a way of doing this?

Answer 1

UpdateSettings(..) has much more pleasant syntax to set up analysis settings.

This is how you can handle your case:

client.UpdateSettings(s => s
    .Index(indexName)
    .Analysis(a => a
        .TokenFilters(f => f.Add("edge_ngram_filter", new EdgeNGramTokenFilter
        {
            MinGram = 2,
            MaxGram = 20
        }))
        .Analyzers(analyzer => analyzer.Add("edge_ngram_analyzer", new CustomAnalyzer
        {
            Tokenizer = "standard",
            Filter = new List<string> {"lowercase", "edge_ngram_filter"}
        }))));

Remember to close index before you will update index settings.

Hope it helps.

UPDATE:

You can achieve this during index creation as well. No need to update settings.

client.CreateIndex(indexName, i => i
    .Analysis(a => a
        .TokenFilters(f => f.Add("edge_ngram_filter", new EdgeNGramTokenFilter
        {
            MinGram = 2,
            MaxGram = 20
        }))
        .Analyzers(analyzer => analyzer.Add("edge_ngram_analyzer", new CustomAnalyzer
        {
            Tokenizer = "standard",
            Filter = new List<string> {"lowercase", "edge_ngram_filter"}
        }))));