Start transform API

POST _transform/<transform_id>/_start

If the Elasticsearch security features are enabled, you must have the following built-in roles and privileges:

For more information, see Security privileges and Built-in roles.

When you start a transform, it creates the destination index if it does not already exist. The number_of_shards is set to 1 and the auto_expand_replicas is set to 0-1.

The transform deduces the mapping definitions from the source indices. For scripted fields, it uses dynamic mappings. If a field in the destination index is created by scripted_metric or bucket_script aggregations, the transform uses dynamic mappings unless a template exists or the destination index already exists. Mapping definitions in the destination index take precedence over dynamic mappings and templates.

When the transform starts, a series of validations occur to ensure its success. If you deferred validation when you created the transform, they occur when you start the transform—​with the exception of privilege checks. When Elasticsearch security features are enabled, the transform remembers which roles the user that created it had at the time of creation and uses those same roles. If those roles do not have the required privileges on the source and destination indices, the transform fails when it attempts unauthorized operations.

POST _transform/ecommerce_transform/_start

When the transform starts, you receive the following results:

{
  "acknowledged" : true
}