Norms

The norms mapping parameter controls whether normalization factors are computed and stored for a field. These factors are used during query scoring to adjust the relevance of the search results. However, storing norms increases the index size and consumes additional memory.

By default, norms is enabled on text fields, for which relevance scoring is important. Fields that do not require these scoring features, such as keyword fields used only for filtering, are configured with norms disabled.

Disabling norms on a field

The following request creates an index named products with the description field as a text field with norms disabled:

PUT /products
{
  "mappings": {
    "properties": {
      "description": {
        "type": "text",
        "norms": false
      }
    }
  }
}

To disable norms on a field in an existing index, use the following request:

PUT /products/_mapping
{
  "properties": {
    "review": {
      "type": "text",
      "norms": false
    }
  }
}

Enabling norms on a field that has norms disabled is impossible and will result in the following error:

{
  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception",
        "reason": "Mapper for [description] conflicts with existing mapper:\n\tCannot update parameter [norms] from [false] to [true]"
      }
    ],
    "type": "illegal_argument_exception",
    "reason": "Mapper for [description] conflicts with existing mapper:\n\tCannot update parameter [norms] from [false] to [true]"
  },
  "status": 400
}