How to create ngrams in only forward direction in Elasticsearch?

Question

Is it possible to create the ngrams like this :

homework -> ho,hom,home,homew,homewo,homewor,homework only ? 

which is only in forward direction ?

Currently its creating all possible ways.

Answer 1

The edge_ngram tokenizer first breaks text down into words whenever it encounters one of a list of specified characters, then it emits N-grams of each word where the start of the N-gram is anchored to the beginning of the word.

Refer to this official documentation to get a detailed explanation on Edge n-grams

Index Mapping:

{
  "settings": {
    "analysis": {
      "analyzer": {
        "my_analyzer": {
          "tokenizer": "my_tokenizer"
        }
      },
      "tokenizer": {
        "my_tokenizer": {
          "type": "edge_ngram",
          "min_gram": 2,
          "max_gram": 10,
          "token_chars": [
            "letter",
            "digit"
          ]
        }
      }
    }
  }
}

Analyze API

Following tokens will be generated:

{
  "analyzer": "my_analyzer",
  "text": "Homework"
}

tokens": [
    {
      "token": "Ho",
      "start_offset": 0,
      "end_offset": 2,
      "type": "word",
      "position": 0
    },
    {
      "token": "Hom",
      "start_offset": 0,
      "end_offset": 3,
      "type": "word",
      "position": 1
    },
    {
      "token": "Home",
      "start_offset": 0,
      "end_offset": 4,
      "type": "word",
      "position": 2
    },
    {
      "token": "Homew",
      "start_offset": 0,
      "end_offset": 5,
      "type": "word",
      "position": 3
    },
    {
      "token": "Homewo",
      "start_offset": 0,
      "end_offset": 6,
      "type": "word",
      "position": 4
    },
    {
      "token": "Homewor",
      "start_offset": 0,
      "end_offset": 7,
      "type": "word",
      "position": 5
    },
    {
      "token": "Homework",
      "start_offset": 0,
      "end_offset": 8,
      "type": "word",
      "position": 6
    }
  ]
}