OpenSearch/docs/reference/indices/templates.asciidoc

[[indices-templates]]
== Index Templates

Index templates allow you to define templates that will automatically be
applied when new indices are created. The templates include both settings and
mappings, and a simple pattern template that controls whether the template
should be applied to the new index.

NOTE: Templates are only applied at index creation time.  Changing a template
will have no impact on existing indices.

For example:

[source,js]
--------------------------------------------------
PUT _template/template_1
{
  "template": "te*",
  "settings": {
    "number_of_shards": 1
  },
  "mappings": {
    "type1": {
      "_source": {
        "enabled": false
      },
      "properties": {
        "host_name": {
          "type": "keyword"
        },
        "created_at": {
          "type": "date",
          "format": "EEE MMM dd HH:mm:ss Z YYYY"
        }
      }
    }
  }
}
--------------------------------------------------
// CONSOLE
// TESTSETUP

NOTE: Index templates provide C-style /* */ block comments. Comments are allowed
everywhere in the JSON document except before to the initial opening curly bracket. 

Defines a template named template_1, with a template pattern of `te*`.
The settings and mappings will be applied to any index name that matches
the `te*` template.

It is also possible to include aliases in an index template as follows:

[source,js]
--------------------------------------------------
PUT _template/template_1
{
    "template" : "te*",
    "settings" : {
        "number_of_shards" : 1
    },
    "aliases" : {
        "alias1" : {},
        "alias2" : {
            "filter" : {
                "term" : {"user" : "kimchy" }
            },
            "routing" : "kimchy"
        },
        "{index}-alias" : {} <1>
    }
}
--------------------------------------------------
// CONSOLE
// TEST[s/^/DELETE _template\/template_1\n/]

<1> the `{index}` placeholder within the alias name will be replaced with the
actual index name that the template gets applied to during index creation.

[float]
[[delete]]
=== Deleting a Template

Index templates are identified by a name (in the above case
`template_1`) and can be deleted as well:

[source,js]
--------------------------------------------------
DELETE /_template/template_1
--------------------------------------------------
// CONSOLE

[float]
[[getting]]
=== Getting templates

Index templates are identified by a name (in the above case
`template_1`) and can be retrieved using the following:

[source,js]
--------------------------------------------------
GET /_template/template_1
--------------------------------------------------
// CONSOLE

You can also match several templates by using wildcards like:

[source,js]
--------------------------------------------------
GET /_template/temp*
GET /_template/template_1,template_2
--------------------------------------------------
// CONSOLE

To get list of all index templates you can run:

[source,js]
--------------------------------------------------
GET /_template
--------------------------------------------------
// CONSOLE

[float]
[[indices-templates-exists]]
=== Templates exists

Used to check if the template exists or not. For example:

[source,js]
-----------------------------------------------
HEAD _template/template_1
-----------------------------------------------
// CONSOLE

The HTTP status code indicates if the template with the given name
exists or not. A status code `200` means it exists, a `404` it does not.

[float]
[[multiple-templates]]
=== Multiple Template Matching

Multiple index templates can potentially match an index, in this case,
both the settings and mappings are merged into the final configuration
of the index. The order of the merging can be controlled using the
`order` parameter, with lower order being applied first, and higher
orders overriding them. For example:

[source,js]
--------------------------------------------------
PUT /_template/template_1
{
    "template" : "*",
    "order" : 0,
    "settings" : {
        "number_of_shards" : 1
    },
    "mappings" : {
        "type1" : {
            "_source" : { "enabled" : false }
        }
    }
}

PUT /_template/template_2
{
    "template" : "te*",
    "order" : 1,
    "settings" : {
        "number_of_shards" : 1
    },
    "mappings" : {
        "type1" : {
            "_source" : { "enabled" : true }
        }
    }
}
--------------------------------------------------
// CONSOLE
// TEST[s/^/DELETE _template\/template_1\n/]

The above will disable storing the `_source` on all `type1` types, but
for indices of that start with `te*`, source will still be enabled.
Note, for mappings, the merging is "deep", meaning that specific
object/property based mappings can easily be added/overridden on higher
order templates, with lower order templates providing the basis.