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Mappings and field types
Mappings tell OpenSearch how to store and index your documents and their fields. You can specify the data type for each field (for example, year as date) to make storage and querying more efficient.
While dynamic mappings automatically add new data and fields, using explicit mappings is recommended. Explicit mappings let you define the exact structure and data types upfront. This helps to maintain data consistency and optimize performance, especially for large datasets or high-volume indexing operations.
For example, with explicit mappings, you can ensure that year is treated as text and age as an integer instead of both being interpreted as integers by dynamic mapping.
Dynamic mapping
When you index a document, OpenSearch adds fields automatically with dynamic mapping. You can also explicitly add fields to an index mapping.
Dynamic mapping types
| Type | Description |
|---|---|
null | A null field can’t be indexed or searched. When a field is set to null, OpenSearch behaves as if the field has no value. |
boolean | OpenSearch accepts true and false as Boolean values. An empty string is equal to false. |
float | A single-precision, 32-bit floating-point number. |
double | A double-precision, 64-bit floating-point number. |
integer | A signed 32-bit number. |
object | Objects are standard JSON objects, which can have fields and mappings of their own. For example, a movies object can have additional properties such as title, year, and director. |
array | OpenSearch does not have a specific array data type. Arrays are represented as a set of values of the same data type (for example, integers or strings) associated with a field. When indexing, you can pass multiple values for a field, and OpenSearch will treat it as an array. Empty arrays are valid and recognized as array fields with zero elements—not as fields with no values. OpenSearch supports querying and filtering arrays, including checking for values, range queries, and array operations like concatenation and intersection. Nested arrays, which may contain complex objects or other arrays, can also be used for advanced data modeling. |
text | A string sequence of characters that represent full-text values. |
keyword | A string sequence of structured characters, such as an email address or ZIP code. |
| date detection string | Enabled by default, if new string fields match a date’s format, then the string is processed as a date field. For example, date: "2012/03/11" is processed as a date. |
| numeric detection string | If disabled, OpenSearch may automatically process numeric values as strings when they should be processed as numbers. When enabled, OpenSearch can process strings into long, integer, short, byte, double, float, half_float, scaled_float, and unsigned_long. Default is disabled. |
Dynamic templates
Dynamic templates are used to define custom mappings for dynamically added fields based on the data type, field name, or field path. They allow you to define a flexible schema for your data that can automatically adapt to changes in the structure or format of the input data.
You can use the following syntax to define a dynamic mapping template:
PUT index
{
"mappings": {
"dynamic_templates": [
{
"fields": {
"mapping": {
"type": "short"
},
"match_mapping_type": "string",
"path_match": "status*"
}
}
]
}
}
This mapping configuration dynamically maps any field with a name starting with status (for example, status_code) to the short data type if the initial value provided during indexing is a string.
Dynamic mapping parameters
The dynamic_templates support the following parameters for matching conditions and mapping rules. The default value is null.
| Parameter | Description |
|---|---|
match_mapping_type | Specifies the JSON data type (for example, string, long, double, object, binary, Boolean, date) that triggers the mapping. |
match | A regular expression used to match field names and apply the mapping. |
unmatch | A regular expression used to exclude field names from the mapping. |
match_pattern | Determines the pattern matching behavior, either regex or simple. Default is simple. |
path_match | Allows you to match nested field paths using a regular expression. |
path_unmatch | Excludes nested field paths from the mapping using a regular expression. |
mapping | The mapping configuration to apply. |
Explicit mapping
If you know exactly which field data types you need to use, then you can specify them in your request body when creating your index, as shown in the following example request:
PUT sample-index1
{
"mappings": {
"properties": {
"year": { "type" : "text" },
"age": { "type" : "integer" },
"director":{ "type" : "text" }
}
}
}
Response
{
"acknowledged": true,
"shards_acknowledged": true,
"index": "sample-index1"
}
To add mappings to an existing index or data stream, you can send a request to the _mapping endpoint using the PUT or POST HTTP method, as shown in the following example request:
POST sample-index1/_mapping
{
"properties": {
"year": { "type" : "text" },
"age": { "type" : "integer" },
"director":{ "type" : "text" }
}
}
You cannot change the mapping of an existing field, you can only modify the field’s mapping parameters.
Mapping parameters
Mapping parameters are used to configure the behavior of index fields. See Mappings and field types for more information.
Mapping limit settings
OpenSearch has certain mapping limits and settings, such as the settings listed in the following table. Settings can be configured based on your requirements.
| Setting | Default value | Allowed value | Type | Description |
|---|---|---|---|---|
index.mapping.nested_fields.limit | 50 | [0,) | Dynamic | Limits the maximum number of nested fields that can be defined in an index mapping. |
index.mapping.nested_objects.limit | 10,000 | [0,) | Dynamic | Limits the maximum number of nested objects that can be created in a single document. |
index.mapping.total_fields.limit | 1,000 | [0,) | Dynamic | Limits the maximum number of fields that can be defined in an index mapping. |
index.mapping.depth.limit | 20 | [1,100] | Dynamic | Limits the maximum depth of nested objects and nested fields that can be defined in an index mapping. |
index.mapping.field_name_length.limit | 50,000 | [1,50000] | Dynamic | Limits the maximum length of field names that can be defined in an index mapping. |
index.mapper.dynamic | true | {true,false} | Dynamic | Determines whether new fields should be dynamically added to a mapping. |
Get a mapping
To get all mappings for one or more indexes, use the following request:
GET <index>/_mapping
In the previous request, <index> may be an index name or a comma-separated list of index names.
To get all mappings for all indexes, use the following request:
GET _mapping
To get a mapping for a specific field, provide the index name and the field name:
GET _mapping/field/<fields>
GET /<index>/_mapping/field/<fields>
Both <index> and <fields> can be specified as either one value or a comma-separated list. For example, the following request retrieves the mapping for the year and age fields in sample-index1:
GET sample-index1/_mapping/field/year,age
The response contains the specified fields:
{
"sample-index1" : {
"mappings" : {
"year" : {
"full_name" : "year",
"mapping" : {
"year" : {
"type" : "text"
}
}
},
"age" : {
"full_name" : "age",
"mapping" : {
"age" : {
"type" : "integer"
}
}
}
}
}
}
Mappings use cases
See Mappings use cases for use case examples, including examples of mapping string fields and ignoring malformed IP addresses.