OpenSearch/docs/reference/mapping/dynamic/templates.asciidoc

[[dynamic-templates]]
=== Dynamic templates

Dynamic templates allow you to define custom mappings that can be applied to
dynamically added fields based on:

* the <<dynamic-mapping,datatype>> detected by Elasticsearch, with <<match-mapping-type,`match_mapping_type`>>.
* the name of the field, with <<match-unmatch,`match` and `unmatch`>> or <<match-pattern,`match_pattern`>>.
* the full dotted path to the field, with <<path-match-unmatch,`path_match` and `path_unmatch`>>.

The original field name `{name}` and the detected datatype
`{dynamic_type`} <<template-variables,template variables>> can be used in
the mapping specification as placeholders.

IMPORTANT: Dynamic field mappings are only added when a field contains a
concrete value -- not `null` or an empty array. This means that if the
`null_value` option  is used in a `dynamic_template`, it will only be applied
after the first document  with a concrete value for the field has been
indexed.

Dynamic templates are specified as an array of named objects:

[source,js]
--------------------------------------------------
  "dynamic_templates": [
    {
      "my_template_name": { <1>
        ...  match conditions ... <2>
        "mapping": { ... } <3>
      }
    },
    ...
  ]
--------------------------------------------------
<1> The template name can be any string value.
<2> The match conditions can include any of : `match_mapping_type`, `match`, `match_pattern`, `unmatch`, `match_path`, `unmatch_path`.
<3> The mapping that the matched field should use.


Templates are processed in order -- the first matching template wins. New
templates can be appended to the end of the list with the
<<indices-put-mapping,PUT mapping>> API.  If a new template has the same
name as an existing template, it will replace the old version.

[[match-mapping-type]]
==== `match_mapping_type`

The `match_mapping_type` matches on the datatype detected by
<<dynamic-field-mapping,dynamic field mapping>>, in other words, the datatype
that Elasticsearch thinks the field should have.  Only the following datatypes
can be automatically detected: `boolean`, `date`, `double`, `long`, `object`,
`string`.  It also accepts `*` to match all datatypes.

For example, if we wanted to map all integer fields as `integer` instead of
`long`, and all `string` fields as both `analyzed` and `not_analyzed`, we
could use the following template:

[source,js]
--------------------------------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "dynamic_templates": [
        {
          "integers": {
            "match_mapping_type": "long",
            "mapping": {
              "type": "integer"
            }
          }
        },
        {
          "strings": {
            "match_mapping_type": "string",
            "mapping": {
              "type": "string",
              "fields": {
                "raw": {
                  "type":  "string",
                  "index": "not_analyzed",
                  "ignore_above": 256
                }
              }
            }
          }
        }
      ]
    }
  }
}

PUT my_index/my_type/1
{
  "my_integer": 5, <1>
  "my_string": "Some string" <2>
}

--------------------------------------------------
// AUTOSENSE
<1> The `my_integer` field is mapped as an `integer`.
<2> The `my_string` field is mapped as an analyzed `string`, with a `not_analyzed` <<multi-fields,multi field>>.


[[match-unmatch]]
==== `match` and `unmatch`

The `match` parameter uses a pattern to match on the fieldname, while
`unmatch` uses a pattern to exclude fields matched by `match`.

The following example matches all `string` fields whose name starts with
`long_` (except for those which end with `_text`) and maps them as `long`
fields:


[source,js]
--------------------------------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "dynamic_templates": [
        {
          "longs_as_strings": {
            "match_mapping_type": "string",
            "match":   "long_*",
            "unmatch": "*_text",
            "mapping": {
              "type": "long"
            }
          }
        }
      ]
    }
  }
}

PUT my_index/my_type/1
{
  "long_num": "5", <1>
  "long_text": "foo" <2>
}
--------------------------------------------------
// AUTOSENSE
<1> The `long_num` field is mapped as a `long`.
<2> The `long_text` field uses the default `string` mapping.

[[match-pattern]]
==== `match_pattern`

The `match_pattern` parameter behaves just like the `match` parameter, but
supports full Java regular expression matching on the field name instead of
simple wildcards, for instance:

[source,js]
--------------------------------------------------
  "match_pattern": "^profit_\d+$"
--------------------------------------------------

[[path-match-unmatch]]
==== `path_match` and `path_unmatch`

The `path_match` and `path_unmatch` parameters work in the same way as `match`
and `unmatch`, but operate on the full dotted path to the field, not just the
final name, e.g. `some_object.*.some_field`.

This example copies the values of any fields in the `name` object to the
top-level `full_name` field, except for the `middle` field:

[source,js]
--------------------------------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "dynamic_templates": [
        {
          "full_name": {
            "path_match":   "name.*",
            "path_unmatch": "*.middle",
            "mapping": {
              "type":       "string",
              "copy_to":    "full_name"
            }
          }
        }
      ]
    }
  }
}

PUT my_index/my_type/1
{
  "name": {
    "first":  "Alice",
    "middle": "Mary",
    "last":   "White"
  }
}
--------------------------------------------------
// AUTOSENSE

[[template-variables]]
==== `{name}` and `{dynamic_type}`

The `{name}` and `{dynamic_type}` placeholders are replaced in the `mapping`
with the field name and detected dynamic type.  The following example sets all
string fields to use an <<analyzer,`analyzer`>> with the same name as the
field, and disables <<doc-values,`doc_values`>> for all non-string fields:

[source,js]
--------------------------------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "dynamic_templates": [
        {
          "named_analyzers": {
            "match_mapping_type": "string",
            "match": "*",
            "mapping": {
              "type": "string",
              "analyzer": "{name}"
            }
          }
        },
        {
          "no_doc_values": {
            "match_mapping_type":"*",
            "mapping": {
              "type": "{dynamic_type}",
              "doc_values": false
            }
          }
        }
      ]
    }
  }
}

PUT my_index/my_type/1
{
  "english": "Some English text", <1>
  "count":   5 <2>
}
--------------------------------------------------
// AUTOSENSE
<1> The `english` field is mapped as a `string` field with the `english` analyzer.
<2> The `count` field is mapped as a `long` field with `doc_values` disabled