OpenSearch/docs/reference/indices/templates.asciidoc

[[indices-templates]]
== Index Templates

Index templates allow to define templates that will automatically be
applied to new indices created. The templates include both settings and
mappings, and a simple pattern template that controls if the template
will be applied to the index created. For example:

[source,js]
--------------------------------------------------
curl -XPUT localhost:9200/_template/template_1 -d '
{
    "template" : "te*",
    "settings" : {
        "number_of_shards" : 1
    },
    "mappings" : {
        "type1" : {
            "_source" : { "enabled" : false }
        }
    }
}
'
--------------------------------------------------

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.

[float]
=== Deleting a Template

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

[source,js]
--------------------------------------------------
curl -XDELETE localhost:9200/_template/template_1
--------------------------------------------------

[float]
=== GETting a Template

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

[source,js]
--------------------------------------------------
curl -XGET localhost:9200/_template/template_1
--------------------------------------------------

You can also match several templates by using wildcards like:

[source,js]
--------------------------------------------------
curl -XGET localhost:9200/_template/temp*
--------------------------------------------------

To get list of all index templates you can use
<<cluster-state,Cluster State>> API
and check for the metadata/templates section of the response.

[float]
=== 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]
--------------------------------------------------
curl -XPUT localhost:9200/_template/template_1 -d '
{
    "template" : "*",
    "order" : 0,
    "settings" : {
        "number_of_shards" : 1
    },
    "mappings" : {
        "type1" : {
            "_source" : { "enabled" : false }
        }
    }
}
'

curl -XPUT localhost:9200/_template/template_2 -d '
{
    "template" : "te*",
    "order" : 1,
    "settings" : {
        "number_of_shards" : 1
    },
    "mappings" : {
        "type1" : {
            "_source" : { "enabled" : true }
        }
    }
}
'
--------------------------------------------------

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.

[float]
=== Config

Index templates can also be placed within the config location
(`path.conf`) under the `templates` directory (note, make sure to place
them on all master eligible nodes). For example, a file called
`template_1.json` can be placed under `config/templates` and it will be
added if it matches an index. Here is a sample of the mentioned file:

[source,js]
--------------------------------------------------
{
    "template_1" : {
        "template" : "*",
        "settings" : {
            "index.number_of_shards" : 2
        },
        "mappings" : {
            "_default_" : {
                "_source" : {
                    "enabled" : false
                }
            },
            "type1" : {
                "_all" : {
                    "enabled" : false
                }
            }
        }
    }
}
--------------------------------------------------