Efficient way to retrieve all _ids in ElasticSearch

Question

What is the fastest way to get all _ids of a certain index from ElasticSearch? Is it possible by using a simple query? One of my index has around 20,000 documents.

Answer 1

Url -> http://localhost:9200///_query
http method -> GET
Query -> {"query": {"match_all": {}}, "size": 30000, "fields": ["_id"]}