elasticsearch/docs/reference/mapping/fields/ignored-field.asciidoc

[[mapping-ignored-field]]
=== `_ignored` field

The `_ignored` field indexes and stores the names of every field in a document
that has been ignored when the document was indexed. This can, for example,
be the case when the field was malformed and <<ignore-malformed,`ignore_malformed`>>
was turned on, or when a `keyword` fields value exceeds its optional
<<ignore-above,`ignore_above`>> setting.

This field is searchable with <<query-dsl-term-query,`term`>>,
<<query-dsl-terms-query,`terms`>> and <<query-dsl-exists-query,`exists`>>
queries, and is returned as part of the search hits.

For instance the below query matches all documents that have one or more fields
that got ignored:

[source,console]
--------------------------------------------------
GET _search
{
  "query": {
    "exists": {
      "field": "_ignored"
    }
  }
}
--------------------------------------------------

Similarly, the below query finds all documents whose `@timestamp` field was
ignored at index time:

[source,console]
--------------------------------------------------
GET _search
{
  "query": {
    "term": {
      "_ignored": "@timestamp"
    }
  }
}
--------------------------------------------------