Search-as-you-type field in Elasticsearch

Introduction

A search-as-you-type field helps users find what they want quickly by showing results while they type. It makes searching faster and easier.

When building a website search box that shows suggestions as you type.

When creating a product catalog where users can find items quickly.

When making a contact list that filters names instantly.

When you want to improve user experience by reducing typing effort.

When you want to handle partial words or prefixes in search queries.

Syntax

Elasticsearch

PUT /my_index
{
  "mappings": {
    "properties": {
      "my_field": {
        "type": "search_as_you_type"
      }
    }
  }
}

The search_as_you_type field type creates special subfields to support fast prefix matching.

You use this field type in your index mapping before adding documents.

Examples

This creates a name field that supports search-as-you-type for product names.

Elasticsearch

PUT /products
{
  "mappings": {
    "properties": {
      "name": {
        "type": "search_as_you_type"
      }
    }
  }
}

This query searches for terms starting with "iph" in the name field and its subfields.

Elasticsearch

GET /products/_search
{
  "query": {
    "multi_match": {
      "query": "iph",
      "type": "bool_prefix",
      "fields": [
        "name",
        "name._2gram",
        "name._3gram"
      ]
    }
  }
}

Sample Program

This example creates an index called library with a title field that supports search-as-you-type. It adds two books and then searches for titles starting with "Grea".

Elasticsearch

PUT /library
{
  "mappings": {
    "properties": {
      "title": {
        "type": "search_as_you_type"
      }
    }
  }
}

POST /library/_doc/1
{
  "title": "The Great Gatsby"
}

POST /library/_doc/2
{
  "title": "Great Expectations"
}

GET /library/_search
{
  "query": {
    "multi_match": {
      "query": "Grea",
      "type": "bool_prefix",
      "fields": [
        "title",
        "title._2gram",
        "title._3gram"
      ]
    }
  }
}

Important Notes

Search-as-you-type fields create hidden subfields with n-grams to speed up prefix searches.

Use multi_match with bool_prefix type to query these fields effectively.

Remember to reindex your data after changing mappings.

Summary

Search-as-you-type fields help users find matches while typing.

Define the field with type: search_as_you_type in your mapping.

Use multi_match queries with bool_prefix to search these fields.