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Mapping
editMapping
editMapping 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.
-
whether the values of all fields in the document should be
indexed into the catch-all
_all
field. - the format of date values.
- custom rules to control the mapping for dynamically added fields.
Mapping Types
editEach index has one or more mapping types, which are used to divide the
documents in an index into logical groups. User documents might be stored in a
user
type, and blog posts in a blogpost
type.
Each mapping type has:
- Meta-fields
-
Meta-fields are used to customize how a document’s metadata associated is
treated. Examples of meta-fields include the document’s
_index
,_type
,_id
, and_source
fields. - Fields or properties
-
Each mapping type contains a list of fields or
properties
pertinent to that type. Auser
type might containtitle
,name
, andage
fields, while ablogpost
type might containtitle
,body
,user_id
andcreated
fields. Fields with the same name in different mapping types in the same index must have the same mapping.
Field datatypes
editEach field has a data type
which can be:
It is often useful to index the same field in different ways for different
purposes. For instance, a string
field could be indexed as
an analyzed
field for full-text search, and as a not_analyzed
field for
sorting or aggregations. Alternatively, you could index a string field with
the standard
analyzer, the
english
analyzer, and the
french
analyzer.
This is the purpose of multi-fields. Most datatypes support multi-fields
via the fields
parameter.
Dynamic mapping
editFields and mapping types do not need to be defined before being used. Thanks
to dynamic mapping, new mapping types and 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
and
nested
fields.
The dynamic mapping rules can be configured to customise the mapping that is used for new types and new fields.
Explicit mappings
editYou 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 mapping types and field mappings when you create an index, and you can add mapping types and fields to an existing index with the PUT mapping API.
Updating existing mappings
editOther than where documented, existing type and field mappings cannot be updated. Changing the mapping would mean invalidating already indexed documents. Instead, you should create a new index with the correct mappings and reindex your data into that index.
Fields are shared across mapping types
editMapping types are used to group fields, but the fields in each mapping type are not independent of each other. Fields with:
- the same name
- in the same index
- in different mapping types
- map to the same field internally,
- and must have the same mapping.
If a title
field exists in both the user
and blogpost
mapping types, the
title
fields must have exactly the same mapping in each type. The only
exceptions to this rule are the copy_to
, dynamic
, enabled
,
ignore_above
, include_in_all
, and properties
parameters, which may
have different settings per field.
Usually, fields with the same name also contain the same type of data, so
having the same mapping is not a problem. When conflicts do arise, these can
be solved by choosing more descriptive names, such as user_title
and
blog_title
.
Example mapping
editA mapping for the example described above could be specified when creating the index, as follows:
PUT my_index { "mappings": { "user": { "_all": { "enabled": false }, "properties": { "title": { "type": "string" }, "name": { "type": "string" }, "age": { "type": "integer" } } }, "blogpost": { "properties": { "title": { "type": "string" }, "body": { "type": "string" }, "user_id": { "type": "string", "index": "not_analyzed" }, "created": { "type": "date", "format": "strict_date_optional_time||epoch_millis" } } } } }
Create an index called |
|
Add mapping types called |
|
Disable the |
|
Specify fields or properties in each mapping type. |
|
Specify the data |