286 lines
8.2 KiB
Plaintext
286 lines
8.2 KiB
Plaintext
[[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 <<mapping-date-format,format>> of date values.
|
|
* custom rules to control the mapping for
|
|
<<dynamic-mapping,dynamically added fields>>.
|
|
|
|
[float]
|
|
[[mapping-type]]
|
|
== Mapping Type
|
|
|
|
Each index has one _mapping type_ which determines how the document will be
|
|
indexed.
|
|
|
|
deprecated::[6.0.0,See <<removal-of-types>>]
|
|
|
|
A mapping type has:
|
|
|
|
<<mapping-fields,Meta-fields>>::
|
|
|
|
Meta-fields are used to customize how a document's metadata associated is
|
|
treated. Examples of meta-fields include the document's
|
|
<<mapping-index-field,`_index`>>, <<mapping-type-field,`_type`>>,
|
|
<<mapping-id-field,`_id`>>, and <<mapping-source-field,`_source`>> fields.
|
|
|
|
<<mapping-types,Fields>> or _properties_::
|
|
|
|
A mapping type contains a list of fields or `properties` pertinent to the
|
|
document.
|
|
|
|
|
|
[float]
|
|
[[field-datatypes]]
|
|
== Field datatypes
|
|
|
|
Each field has a data `type` which can be:
|
|
|
|
* a simple type like <<text,`text`>>, <<keyword,`keyword`>>, <<date,`date`>>, <<number,`long`>>,
|
|
<<number,`double`>>, <<boolean,`boolean`>> or <<ip,`ip`>>.
|
|
* a type which supports the hierarchical nature of JSON such as
|
|
<<object,`object`>> or <<nested,`nested`>>.
|
|
* or a specialised type like <<geo-point,`geo_point`>>,
|
|
<<geo-shape,`geo_shape`>>, or <<completion-suggester,`completion`>>.
|
|
|
|
It is often useful to index the same field in different ways for different
|
|
purposes. For instance, a `string` field could be <<mapping-index,indexed>> 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 <<analysis-standard-analyzer,`standard` analyzer>>, the
|
|
<<english-analyzer,`english`>> analyzer, and the
|
|
<<french-analyzer,`french` analyzer>>.
|
|
|
|
This is the purpose of _multi-fields_. Most datatypes support multi-fields
|
|
via the <<multi-fields>> parameter.
|
|
|
|
[[mapping-limit-settings]]
|
|
[float]
|
|
=== Settings to prevent mappings explosion
|
|
|
|
Defining too many fields in an index is a condition that can lead to a
|
|
mapping explosion, which can cause out of memory errors and difficult
|
|
situations to recover from. This problem may be more common than expected.
|
|
As an example, consider a situation in which every new document inserted
|
|
introduces new fields. This is quite common with dynamic mappings.
|
|
Every time a document contains new fields, those will end up in the index's
|
|
mappings. This isn't worrying for a small amount of data, but it can become a
|
|
problem as the mapping grows.
|
|
The following settings allow you to limit the number of field mappings that
|
|
can be created manually or dynamically, in order to prevent bad 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
|
|
<<search-settings,`indices.query.bool.max_clause_count`>> setting, which
|
|
limits the maximum number of <<query-dsl-bool-query,boolean clauses>> in a query.
|
|
====
|
|
|
|
`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. The default is `20`.
|
|
|
|
`index.mapping.nested_fields.limit`::
|
|
The maximum number of distinct `nested` mappings in an index, defaults to `50`.
|
|
|
|
`index.mapping.nested_objects.limit`::
|
|
The maximum number of `nested` JSON objects within a single document across
|
|
all nested types, defaults to 10000.
|
|
|
|
`index.mapping.field_name_length.limit`::
|
|
Setting for the maximum length of a field name. The default value is
|
|
Long.MAX_VALUE (no limit). 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.
|
|
|
|
[float]
|
|
== 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 <<object,`object`>> and <<nested,`nested`>> fields.
|
|
|
|
The <<dynamic-mapping,dynamic mapping>> rules can be configured to customise
|
|
the mapping that is used for new fields.
|
|
|
|
[float]
|
|
== 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 <<create-mapping,create an index>> and
|
|
<<add-field-mapping,add fields to an existing index>>.
|
|
|
|
[float]
|
|
[[create-mapping]]
|
|
== Create an index with an explicit mapping
|
|
|
|
You can use the <<indices-create-index,create index>> API to create a new index
|
|
with an explicit mapping.
|
|
|
|
[source,console]
|
|
----
|
|
PUT /my-index
|
|
{
|
|
"mappings": {
|
|
"properties": {
|
|
"age": { "type": "integer" }, <1>
|
|
"email": { "type": "keyword" }, <2>
|
|
"name": { "type": "text" } <3>
|
|
}
|
|
}
|
|
}
|
|
----
|
|
|
|
<1> Creates `age`, an <<number,`integer`>> field
|
|
<2> Creates `email`, a <<keyword,`keyword`>> field
|
|
<3> Creates `name`, a <<text,`text`>> field
|
|
|
|
[float]
|
|
[[add-field-mapping]]
|
|
== Add a field to an existing mapping
|
|
|
|
You can use the <<indices-put-mapping, put mapping>> API to add one or more new
|
|
fields to an existing index.
|
|
|
|
The following example adds `employee-id`, a `keyword` field with an
|
|
<<mapping-index,`index`>> 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/_mapping
|
|
{
|
|
"properties": {
|
|
"employee-id": {
|
|
"type": "keyword",
|
|
"index": false
|
|
}
|
|
}
|
|
}
|
|
----
|
|
// TEST[continued]
|
|
|
|
[float]
|
|
[[update-mapping]]
|
|
=== Update the mapping of a field
|
|
|
|
include::{docdir}/indices/put-mapping.asciidoc[tag=change-field-mapping]
|
|
|
|
include::{docdir}/indices/put-mapping.asciidoc[tag=rename-field]
|
|
|
|
[float]
|
|
[[view-mapping]]
|
|
== View the mapping of an index
|
|
|
|
You can use the <<indices-get-mapping, get mapping>> API to view the mapping of
|
|
an existing index.
|
|
|
|
[source,console]
|
|
----
|
|
GET /my-index/_mapping
|
|
----
|
|
// TEST[continued]
|
|
|
|
The API returns the following response:
|
|
|
|
[source,console-result]
|
|
----
|
|
{
|
|
"my-index" : {
|
|
"mappings" : {
|
|
"properties" : {
|
|
"age" : {
|
|
"type" : "integer"
|
|
},
|
|
"email" : {
|
|
"type" : "keyword"
|
|
},
|
|
"employee-id" : {
|
|
"type" : "keyword",
|
|
"index" : false
|
|
},
|
|
"name" : {
|
|
"type" : "text"
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
----
|
|
|
|
|
|
[float]
|
|
[[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 <<indices-get-field-mapping, get field mapping>> 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/_mapping/field/employee-id
|
|
----
|
|
// TEST[continued]
|
|
|
|
The API returns the following response:
|
|
|
|
[source,console-result]
|
|
----
|
|
{
|
|
"my-index" : {
|
|
"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[]
|