OpenSearch/docs/reference/transform/apis/preview-transform.asciidoc

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[role="xpack"]
[testenv="basic"]
[[preview-transform]]
=== Preview {transform} API
[subs="attributes"]
++++
<titleabbrev>Preview {transform}</titleabbrev>
++++
Previews a {transform}.
[[preview-transform-request]]
==== {api-request-title}
`POST _transform/_preview`
[[preview-transform-prereq]]
==== {api-prereq-title}
If the {es} {security-features} are enabled, you must have the following
privileges:
* `manage_transform`
* source index: `read`, `view_index_metadata`
The built-in `transform_admin` role has the `manage_transform` privilege.
For more information, see <<security-privileges>> and <<built-in-roles>>.
[[preview-transform-desc]]
==== {api-description-title}
This API generates a preview of the results that you will get when you run the
<<put-transform,create {transforms} API>> with the same
configuration. It returns a maximum of 100 results. The calculations are based
on all the current data in the source index.
It also generates a list of mappings and settings for the destination index.
If the destination index does not exist when you start a {transform}, these are
the mappings and settings that are used. These values are determined based on
the field types of the source index and the {transform} aggregations.
TIP: There are some <<transform-aggresponse-limitations,limitations>> that
might result in poor mappings. As a work-around, create the destination index
or an index template with your preferred mappings before you start the
{transform}.
[role="child_attributes"]
[[preview-transform-request-body]]
==== {api-request-body-title}
`description`::
(Optional, string) Free text description of the {transform}.
//Begin dest
`dest`::
(Optional, object)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=dest]
+
.Properties of `dest`
[%collapsible%open]
====
`index`:::
(Optional, string)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=dest-index]
`pipeline`:::
(Optional, string)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=dest-pipeline]
====
//End dest
`frequency`::
(Optional, <<time-units, time units>>)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=frequency]
//Begin pivot
`pivot`::
(Required, object)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=pivot]
+
.Properties of `pivot`
[%collapsible%open]
====
`aggregations` or `aggs`:::
(Required, object)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=pivot-aggs]
`group_by`:::
(Required, object)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=pivot-group-by]
====
//End pivot
//Begin source
`source`::
(Required, object)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=source-transforms]
+
.Properties of `source`
[%collapsible%open]
====
`index`:::
(Required, string or array)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=source-index-transforms]
`query`:::
(Optional, object)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=source-query-transforms]
====
//End source
//Begin sync
`sync`::
(Optional, object)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=sync]
+
.Properties of `sync`
[%collapsible%open]
====
//Begin sync.time
`time`:::
(Optional, object)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=sync-time]
+
.Properties of `analysis_config`
[%collapsible%open]
=====
`delay`::::
(Optional, <<time-units, time units>>)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=sync-time-delay]
`field`::::
(Optional, string)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=sync-time-field]
=====
//End sync.time
====
//End sync
//Begin settings
`settings`::
(Optional, object)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=transform-settings]
+
.Properties of `settings`
[%collapsible%open]
====
`docs_per_second`:::
(Optional, float)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=transform-settings-docs-per-second]
`max_page_search_size`:::
(Optional, integer)
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=transform-settings-max-page-search-size]
====
//End settings
[role="child_attributes"]
[[preview-transform-response]]
==== {api-response-body-title}
`preview`::
(array) An array of documents. In particular, they are the JSON representation
of the documents that would be created in the destination index by the
{transform}.
//Begin generated_dest_index
`generated_dest_index`::
(object) Contains details about the destination index.
+
.Properties of `generated_dest_index`
[%collapsible%open]
====
`aliases`:::
(object) The aliases for the destination index.
`mappings`:::
(object) The <<mapping,mappings>> for each document in the destination index.
`settings`:::
(object) The <<index-modules-settings,index settings>> for the destination index.
====
//End generated_dest_index
==== {api-examples-title}
[source,console]
--------------------------------------------------
POST _transform/_preview
{
"source": {
"index": "kibana_sample_data_ecommerce"
},
"pivot": {
"group_by": {
"customer_id": {
"terms": {
"field": "customer_id"
}
}
},
"aggregations": {
"max_price": {
"max": {
"field": "taxful_total_price"
}
}
}
}
}
--------------------------------------------------
// TEST[skip:set up sample data]
The data that is returned for this example is as follows:
[source,js]
----
{
"preview" : [
{
"max_price" : 171.0,
"customer_id" : "10"
},
{
"max_price" : 233.0,
"customer_id" : "11"
},
{
"max_price" : 200.0,
"customer_id" : "12"
}
...
],
"generated_dest_index" : {
"mappings" : {
"_meta" : {
"_transform" : {
"transform" : "transform-preview",
"version" : {
"created" : "7.7.0"
},
"creation_date_in_millis" : 1584738236757
},
"created_by" : "transform"
},
"properties" : {
"max_price" : {
"type" : "half_float"
},
"customer_id" : {
"type" : "keyword"
}
}
},
"settings" : {
"index" : {
"number_of_shards" : "1",
"auto_expand_replicas" : "0-1"
}
},
"aliases" : { }
}
}
----
// NOTCONSOLE