OpenSearch/docs/reference/mapping/dynamic/default-mapping.asciidoc

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[[default-mapping]]
=== `_default_` mapping
The default mapping, which will be used as the base mapping for any new
mapping types, can be customised by adding a mapping type with the name
`_default_` to an index, either when
<<indices-create-index,creating the index>> or later on with the
<<indices-put-mapping,PUT mapping>> API.
[source,js]
--------------------------------------------------
PUT my_index
{
"mappings": {
"_default_": { <1>
"_source": {
"enabled": false
}
},
"user": {}, <2>
"blogpost": { <3>
"_source": {
"enabled": true
}
}
}
}
--------------------------------------------------
// CONSOLE
<1> The `_default_` mapping defaults the <<mapping-source-field,`_source`>> field to disabled.
<2> The `user` type inherits the settings from `_default_`.
<3> The `blogpost` type overrides the defaults and enables the <<mapping-source-field,`_source`>> field.
NOTE: When updating the `_default_` mapping with the
<<indices-put-mapping,PUT mapping>> API, the new mapping is not merged with
the existing mapping. Instead, the new `_default_` mapping replaces the
existing one.
While the `_default_` mapping can be updated after an index has been created,
the new defaults will only affect mapping types that are created afterwards.
The `_default_` mapping can be used in conjunction with
<<indices-templates,Index templates>> to control dynamically created types
within automatically created indices:
[source,js]
--------------------------------------------------
PUT _template/logging
{
"index_patterns": ["logs-*"], <1>
"settings": { "number_of_shards": 1 }, <2>
"mappings": {
"_default_": {
"_field_names": { <3>
"enabled": false
},
"dynamic_templates": [
{
"strings": { <4>
"match_mapping_type": "string",
"mapping": {
"type": "text",
"fields": {
"raw": {
"type": "keyword",
"ignore_above": 256
}
}
}
}
}
]
}
}
}
PUT logs-2015.10.01/event/1
{ "message": "error:16" }
--------------------------------------------------
// CONSOLE
<1> The `logging` template will match any indices beginning with `logs-`.
<2> Matching indices will be created with a single primary shard.
<3> The `_field_names` field will be disabled by default for new type mappings.
<4> String fields will be created with a `text` main field, and a `keyword` `.raw` field.