[[mapping]] = Mapping [partintro] -- Mapping is the process of defining how a document, and the fields it contains, are stored and indexed. For instance, use mappings to define: * which string fields should be treated as full text fields. * which fields contain numbers, dates, or geolocations. * the <> of date values. * custom rules to control the mapping for <>. A mapping definition has: <>:: Meta-fields are used to customize how a document's associated metadata is treated. Examples of meta-fields include the document's <>, <>, and <> fields. <> or _properties_:: A mapping contains a list of fields or `properties` pertinent to the document. NOTE: Before 7.0.0, the 'mappings' definition used to include a type name. For more details, please see <>. [discrete] [[field-datatypes]] == Field data types Each field has a data `type` which can be: * a simple type like <>, <>, <>, <>, <>, <> or <>. * a type which supports the hierarchical nature of JSON such as <> or <>. * or a specialised type like <>, <>, or <>. It is often useful to index the same field in different ways for different purposes. For instance, a `string` field could be <> as a `text` field for full-text search, and as a `keyword` field for sorting or aggregations. Alternatively, you could index a string field with the <>, the <> analyzer, and the <>. This is the purpose of _multi-fields_. Most data types support multi-fields via the <> parameter. [[mapping-limit-settings]] [discrete] === Settings to prevent mappings explosion Defining too many fields in an index can lead to a mapping explosion, which can cause out of memory errors and difficult situations to recover from. Consider a situation where every new document inserted introduces new fields, such as with <>. Each new field is added to the index mapping, which can become a problem as the mapping grows. Use the following settings to limit the number of field mappings (created manually or dynamically) and prevent documents from causing a mapping explosion: `index.mapping.total_fields.limit`:: The maximum number of fields in an index. Field and object mappings, as well as field aliases count towards this limit. The default value is `1000`. + [IMPORTANT] ==== The limit is in place to prevent mappings and searches from becoming too large. Higher values can lead to performance degradations and memory issues, especially in clusters with a high load or few resources. If you increase this setting, we recommend you also increase the <> setting, which limits the maximum number of <> in a query. ==== + [TIP] ==== If your field mappings contain a large, arbitrary set of keys, consider using the <> data type. ==== `index.mapping.depth.limit`:: The maximum depth for a field, which is measured as the number of inner objects. For instance, if all fields are defined at the root object level, then the depth is `1`. If there is one object mapping, then the depth is `2`, etc. Default is `20`. // tag::nested-fields-limit[] `index.mapping.nested_fields.limit`:: The maximum number of distinct `nested` mappings in an index. The `nested` type should only be used in special cases, when arrays of objects need to be queried independently of each other. To safeguard against poorly designed mappings, this setting limits the number of unique `nested` types per index. Default is `50`. // end::nested-fields-limit[] // tag::nested-objects-limit[] `index.mapping.nested_objects.limit`:: The maximum number of nested JSON objects that a single document can contain across all `nested` types. This limit helps to prevent out of memory errors when a document contains too many nested objects. Default is `10000`. // end::nested-objects-limit[] `index.mapping.field_name_length.limit`:: Setting for the maximum length of a field name. This setting isn't really something that addresses mappings explosion but might still be useful if you want to limit the field length. It usually shouldn't be necessary to set this setting. The default is okay unless a user starts to add a huge number of fields with really long names. Default is `Long.MAX_VALUE` (no limit). [discrete] == Dynamic mapping Fields and mapping types do not need to be defined before being used. Thanks to _dynamic mapping_, new field names will be added automatically, just by indexing a document. New fields can be added both to the top-level mapping type, and to inner <> and <> fields. The <> rules can be configured to customise the mapping that is used for new fields. [discrete] == Explicit mappings You know more about your data than Elasticsearch can guess, so while dynamic mapping can be useful to get started, at some point you will want to specify your own explicit mappings. You can create field mappings when you <> and <>. [discrete] [[create-mapping]] == Create an index with an explicit mapping You can use the <> API to create a new index with an explicit mapping. [source,console] ---- PUT /my-index-000001 { "mappings": { "properties": { "age": { "type": "integer" }, <1> "email": { "type": "keyword" }, <2> "name": { "type": "text" } <3> } } } ---- <1> Creates `age`, an <> field <2> Creates `email`, a <> field <3> Creates `name`, a <> field [discrete] [[add-field-mapping]] == Add a field to an existing mapping You can use the <> API to add one or more new fields to an existing index. The following example adds `employee-id`, a `keyword` field with an <> mapping parameter value of `false`. This means values for the `employee-id` field are stored but not indexed or available for search. [source,console] ---- PUT /my-index-000001/_mapping { "properties": { "employee-id": { "type": "keyword", "index": false } } } ---- // TEST[continued] [discrete] [[update-mapping]] === Update the mapping of a field include::{es-repo-dir}/indices/put-mapping.asciidoc[tag=change-field-mapping] include::{es-repo-dir}/indices/put-mapping.asciidoc[tag=rename-field] [discrete] [[view-mapping]] == View the mapping of an index You can use the <> API to view the mapping of an existing index. [source,console] ---- GET /my-index-000001/_mapping ---- // TEST[continued] The API returns the following response: [source,console-result] ---- { "my-index-000001" : { "mappings" : { "properties" : { "age" : { "type" : "integer" }, "email" : { "type" : "keyword" }, "employee-id" : { "type" : "keyword", "index" : false }, "name" : { "type" : "text" } } } } } ---- [discrete] [[view-field-mapping]] == View the mapping of specific fields If you only want to view the mapping of one or more specific fields, you can use the <> API. This is useful if you don't need the complete mapping of an index or your index contains a large number of fields. The following request retrieves the mapping for the `employee-id` field. [source,console] ---- GET /my-index-000001/_mapping/field/employee-id ---- // TEST[continued] The API returns the following response: [source,console-result] ---- { "my-index-000001" : { "mappings" : { "employee-id" : { "full_name" : "employee-id", "mapping" : { "employee-id" : { "type" : "keyword", "index" : false } } } } } } ---- -- include::mapping/removal_of_types.asciidoc[] include::mapping/types.asciidoc[] include::mapping/fields.asciidoc[] include::mapping/params.asciidoc[] include::mapping/dynamic-mapping.asciidoc[]