[[date-index-name-processor]]
=== Date Index Name Processor

The purpose of this processor is to point documents to the right time based index based
on a date or timestamp field in a document by using the <<date-math-index-names, date math index name support>>.

The processor sets the `_index` meta field with a date math index name expression based on the provided index name
prefix, a date or timestamp field in the documents being processed and the provided date rounding.

First, this processor fetches the date or timestamp from a field in the document being processed. Optionally,
date formatting can be configured on how the field's value should be parsed into a date. Then this date,
the provided index name prefix and the provided date rounding get formatted into a date math index name expression.
Also here optionally date formatting can be specified on how the date should be formatted into a date math index name
expression.

An example pipeline that points documents to a monthly index that starts with a `myindex-` prefix based on a
date in the `date1` field:

[source,console]
--------------------------------------------------
PUT _ingest/pipeline/monthlyindex
{
  "description": "monthly date-time index naming",
  "processors" : [
    {
      "date_index_name" : {
        "field" : "date1",
        "index_name_prefix" : "myindex-",
        "date_rounding" : "M"
      }
    }
  ]
}
--------------------------------------------------


Using that pipeline for an index request:

[source,console]
--------------------------------------------------
PUT /myindex/_doc/1?pipeline=monthlyindex
{
  "date1" : "2016-04-25T12:02:01.789Z"
}
--------------------------------------------------
// TEST[continued]

[source,console-result]
--------------------------------------------------
{
  "_index" : "myindex-2016-04-01",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 1,
  "result" : "created",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 55,
  "_primary_term" : 1
}
--------------------------------------------------
// TESTRESPONSE[s/"_seq_no" : \d+/"_seq_no" : $body._seq_no/ s/"_primary_term" : 1/"_primary_term" : $body._primary_term/]


The above request will not index this document into the `myindex` index, but into the `myindex-2016-04-01` index because
it was rounded by month. This is because the date-index-name-processor overrides the `_index` property of the document.

To see the date-math value of the index supplied in the actual index request which resulted in the above document being
indexed into `myindex-2016-04-01` we can inspect the effects of the processor using a simulate request.


[source,console]
--------------------------------------------------
POST _ingest/pipeline/_simulate
{
  "pipeline" :
  {
    "description": "monthly date-time index naming",
    "processors" : [
      {
        "date_index_name" : {
          "field" : "date1",
          "index_name_prefix" : "myindex-",
          "date_rounding" : "M"
        }
      }
    ]
  },
  "docs": [
    {
      "_source": {
        "date1": "2016-04-25T12:02:01.789Z"
      }
    }
  ]
}
--------------------------------------------------

and the result:

[source,console-result]
--------------------------------------------------
{
  "docs" : [
    {
      "doc" : {
        "_id" : "_id",
        "_index" : "<myindex-{2016-04-25||/M{yyyy-MM-dd|UTC}}>",
        "_type" : "_doc",
        "_source" : {
          "date1" : "2016-04-25T12:02:01.789Z"
        },
        "_ingest" : {
          "timestamp" : "2016-11-08T19:43:03.850+0000"
        }
      }
    }
  ]
}
--------------------------------------------------
// TESTRESPONSE[s/2016-11-08T19:43:03.850\+0000/$body.docs.0.doc._ingest.timestamp/]

The above example shows that `_index` was set to `<myindex-{2016-04-25||/M{yyyy-MM-dd|UTC}}>`. Elasticsearch
understands this to mean `2016-04-01` as is explained in the <<date-math-index-names, date math index name documentation>>

[[date-index-name-options]]
.Date index name options
[options="header"]
|======
| Name                   | Required  | Default                      | Description
| `field`                | yes       | -                            | The field to get the date or timestamp from.
| `index_name_prefix`    | no        | -                            | A prefix of the index name to be prepended before the printed date. Supports <<accessing-template-fields,template snippets>>.
| `date_rounding`        | yes       | -                            | How to round the date when formatting the date into the index name. Valid values are: `y` (year), `M` (month), `w` (week), `d` (day), `h` (hour), `m` (minute) and `s` (second). Supports <<accessing-template-fields,template snippets>>.
| `date_formats`         | no        | yyyy-MM-dd+++'T'+++HH:mm:ss.SSSXX  | An array of the expected date formats for parsing dates / timestamps in the document being preprocessed. Can be a java time pattern or one of the following formats: ISO8601, UNIX, UNIX_MS, or TAI64N.
| `timezone`             | no        | UTC                          | The timezone to use when parsing the date and when date math index supports resolves expressions into concrete index names.
| `locale`               | no        | ENGLISH                      | The locale to use when parsing the date from the document being preprocessed, relevant when parsing month names or week days.
| `index_name_format`    | no        | yyyy-MM-dd                   | The format to be used when printing the parsed date into the index name. A valid java time pattern is expected here. Supports <<accessing-template-fields,template snippets>>.
include::common-options.asciidoc[]
|======