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

Edit: Please read @Aleck Landgraf's Answer, too

You just want the elasticsearch-internal _id field? Or an id field from within your documents?

For the former, try

curl http://localhost:9200/index/type/_search?pretty=true -d ' {      "query" : {          "match_all" : {}      },     "stored_fields": [] } ' 

Note 2017 Update: The post originally included "fields": [] but since then the name has changed and stored_fields is the new value.

The result will contain only the "metadata" of your documents

{   "took" : 7,   "timed_out" : false,   "_shards" : {     "total" : 5,     "successful" : 5,     "failed" : 0   },   "hits" : {     "total" : 4,     "max_score" : 1.0,     "hits" : [ {       "_index" : "index",       "_type" : "type",       "_id" : "36",       "_score" : 1.0     }, {       "_index" : "index",       "_type" : "type",       "_id" : "38",       "_score" : 1.0     }, {       "_index" : "index",       "_type" : "type",       "_id" : "39",       "_score" : 1.0     }, {       "_index" : "index",       "_type" : "type",       "_id" : "34",       "_score" : 1.0     } ]   } } 

For the latter, if you want to include a field from your document, simply add it to the fields array

curl http://localhost:9200/index/type/_search?pretty=true -d ' {      "query" : {          "match_all" : {}      },     "fields": ["document_field_to_be_returned"] } '