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

For Python users: the Python Elasticsearch client provides a convenient abstraction for the scroll API:

from elasticsearch import Elasticsearch, helpers
client = Elasticsearch()

query = {
    "query": {
        "match_all": {}
    }
}

scan = helpers.scan(client, index=index, query=query, scroll='1m', size=100)

for doc in scan:
    # do something