Counting number of documents using Elasticsearch

If _search must be used instead of _count, and you're on Elasticsearch 7.0+, setting size: 0 and track_total_hits: true will provide the same info as _count

GET my-index/_search
{
  "query": { "term": { "field": { "value": "xyz" } } },
  "size": 0,
  "track_total_hits": true
}


{
  "took" : 612,
  "timed_out" : false,
  "_shards" : {
    "total" : 629,
    "successful" : 629,
    "skipped" : 524,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 29349466,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  }
}

See Elasticsearch 7.0 Breaking changes

Probably _count is a bit faster since it doesn't have to execute a full query with ranking and result fetching and can simply return the size.

It would be interesting to know a bit more about how you manage to get different results though. For that I need more information like what exact queries you are sending and if any indexing is going on on the index.

But suppose that you do the following

1. index some documents
2. refresh the index

_search and _count (with a match all query) should return the same total. If not, that'd be very weird.