[[norms]]
=== `norms`

Norms store various normalization factors that are later used at query time
in order to compute the score of a document relatively to a query.

Although useful for scoring, norms also require quite a lot of disk
(typically in the order of one byte per document per field in your index, even
for documents that don't have this specific field). As a consequence, if you
don't need scoring on a specific field, you should disable norms on that
field. In  particular, this is the case for fields that are used solely for
filtering or aggregations.

TIP: The `norms` setting must have the same setting for fields of the
same name in the same index.  Norms can be disabled on existing fields using
the <<indices-put-mapping,PUT mapping API>>.

Norms can be disabled (but not reenabled) after the fact, using the
<<indices-put-mapping,PUT mapping API>> like so:

[source,js]
------------
PUT my_index/_mapping/_doc
{
  "properties": {
    "title": {
      "type": "text",
      "norms": false
    }
  }
}
------------
// CONSOLE
// TEST[s/^/PUT my_index\n/]

NOTE: Norms will not be removed instantly, but will be removed as old segments
are merged into new segments as you continue indexing new documents. Any score
computation on a field that has had norms removed might return inconsistent
results since some documents won't have norms anymore while other documents
might still have norms.
