How to make elastic plugin to search by substring with stemming

[Izayda]

This example is for russian language, but can be easily adopted to any other by changing russian words to your language.

const options: ElasticsearchOptions = {
  // ...
  indexSettings: {
    index: {
      max_result_window: 50000
    },
    analysis: {
      analyzer: {
        custom_autocomplete_analyzer: {
          tokenizer: 'standard',
          filter: [
            'lowercase',
            'ngram',
            `russian_stop`,
            `russian_stemmer`
          ]
        },
        custom_search_analyzer: {
          tokenizer: 'standard',
          filter: [
            'lowercase',
            `russian_stemmer`
          ]
        }
      },
      filter: {
        ngram: {
          type: 'edge_ngram',
          min_gram: 2,
          max_gram: 12
        },
        russian_stop: {
          type: `stop`,
          stopwords: `_russian_`
        },
        russian_stemmer: {
          type: `stemmer`,
          language: `russian`
        }

      }
    }
  },
  indexMappingProperties: {
    productName: {
      type: 'text',
      analyzer: 'custom_autocomplete_analyzer',
      search_analyzer: `custom_search_analyzer`,
      fields: {
        keyword: {
          type: 'keyword',
          ignore_above: 256,
        }
      }
    },
    productVariantName: {
      type: 'text',
      analyzer: 'custom_autocomplete_analyzer',
      search_analyzer: `custom_search_analyzer`,
      fields: {
        keyword: {
          type: 'keyword',
          ignore_above: 256,
        }
      }
    },
    sku: {
      type: 'text',
      analyzer: 'custom_autocomplete_analyzer',
      search_analyzer: `custom_search_analyzer`,
      fields: {
        keyword: {
          type: 'keyword',
          ignore_above: 256,
        }
      }
    },
    description: {
      type: 'text',
      analyzer: 'custom_autocomplete_analyzer',
      search_analyzer: `custom_search_analyzer`,
      fields: {
        keyword: {
          type: 'keyword',
          ignore_above: 256,
        }
      }
    },
  }
}