Dynamic Field Names

Sometimes field names are dynamic: every document may introduce a different key (user-supplied tags, attribute maps, and other structures whose names are many and not known in advance). Adding each such name as its own concrete field would make the schema grow without bound.

Dynamic field names solve this by enabling _namespace on the containing field. The varying names underneath no longer add concrete fields to the schema; they are all folded into a single shared field and stay searchable by name.

PUT /test_dynamic_names/1?commit

{
  "tags": {
    "_namespace": true,
    "color": "red",
    "size": "large",
    "shape": "round"
  }
}

No matter how many different keys later documents put under tags, the schema gains a single namespaced tags field rather than one concrete field per key. Each key stays directly queryable by its name:

SEARCH /test_dynamic_names/

{
  "_query": {
    "tags.color": "red"
  }
}

When the dynamic names are not a flat set of keys but a nested tree, and you need to match them by path (with partial paths, datatype rules, and dedicated query operators), that is what Namespaces add on top of dynamic field names; see that page and Namespace Queries for the details.