Dynamic templates in Elasticsearch

Introduction

Dynamic templates help you tell Elasticsearch how to automatically set the type and settings for fields when new data comes in. This saves time and keeps your data organized without manually defining every field.

When you want Elasticsearch to automatically detect and map new fields in your data.

When your data has many fields with similar patterns and you want to apply the same settings to them.

When you want to control how unknown or new fields are indexed without writing full mappings.

When you want to avoid errors from unexpected field types in your documents.

When you want to optimize search and storage by setting specific types for dynamic fields.

Syntax

Elasticsearch

{
  "mappings": {
    "dynamic_templates": [
      {
        "template_name": {
          "match": "pattern*",
          "mapping": {
            "type": "type_name",
            "other_setting": "value"
          }
        }
      }
    ]
  }
}

dynamic_templates is an array of templates.

Each template has a name and defines a match pattern and the mapping to apply.

Examples

This template maps all string fields to the keyword type automatically.

Elasticsearch

{
  "mappings": {
    "dynamic_templates": [
      {
        "strings_as_keywords": {
          "match_mapping_type": "string",
          "mapping": {
            "type": "keyword"
          }
        }
      }
    ]
  }
}

This template matches any field ending with _date and maps it as a date with a specific format.

Elasticsearch

{
  "mappings": {
    "dynamic_templates": [
      {
        "dates": {
          "match": "*_date",
          "mapping": {
            "type": "date",
            "format": "yyyy-MM-dd"
          }
        }
      }
    ]
  }
}

This template maps fields starting with id_ as long integers.

Elasticsearch

{
  "mappings": {
    "dynamic_templates": [
      {
        "long_fields": {
          "match": "id_*",
          "mapping": {
            "type": "long"
          }
        }
      }
    ]
  }
}

Sample Program

This example shows two dynamic templates: one that maps all string fields as keyword type, and another that maps fields ending with _date as dates with a specific format. When you index a document with these fields, Elasticsearch applies these rules automatically.

Elasticsearch

{
  "mappings": {
    "dynamic_templates": [
      {
        "strings_as_keywords": {
          "match_mapping_type": "string",
          "mapping": {
            "type": "keyword"
          }
        }
      },
      {
        "dates": {
          "match": "*_date",
          "mapping": {
            "type": "date",
            "format": "yyyy-MM-dd"
          }
        }
      }
    ]
  }
}

// Example document to index:
// {
//   "user": "alice",
//   "signup_date": "2024-06-01",
//   "comment": "hello world"
// }

// Resulting mapping:
// "user" and "comment" fields are mapped as keyword (because they are strings)
// "signup_date" is mapped as date with format yyyy-MM-dd

Important Notes

Dynamic templates are checked in order, so the first matching template is applied.

You can use match, unmatch, match_mapping_type to control which fields the template applies to.

Dynamic templates help avoid mapping conflicts and make your index flexible.

Summary

Dynamic templates let Elasticsearch automatically map new fields based on rules you set.

They save time and keep your data organized without manual mapping for every field.

Use patterns to match field names or types and define how they should be indexed.