Elasticsearch Java API - How to get the number of documents without retrieving the documents

Question

I need to get the number of documents in an index. not the documents themselves, but just this "how many" .

What's the best way to do that?

There is https://www.elastic.co/guide/en/elasticsearch/reference/current/search-count.html. but I'm looking to do this in Java.

There also is https://www.elastic.co/guide/en/elasticsearch/client/java-api/2.4/count.html, but it seems way old.

I can get all the documents in the given index and come up with "how many". But there must be a better way.

Solution 1

Use the search API, but set it to return no documents and retrieve the count of hits from the SearchResponse object it returns.

For example:

import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.action.search.SearchType;
import org.elasticsearch.index.query.QueryBuilders.*;

SearchResponse response = client.prepareSearch("your_index_goes_here")
    .setTypes("YourTypeGoesHere")
    .setQuery(QueryBuilders.termQuery("some_field", "some_value"))
    .setSize(0) // Don't return any documents, we don't need them.
    .get();

SearchHits hits = response.getHits();
long hitsCount = hits.getTotalHits();

Solution 2

Elastic - Indices Stats

Indices level stats provide statistics on different operations happening on an index. The API provides statistics on the index level scope (though most stats can also be retrieved using node level scope).

prepareStats(indexName) client.admin().indices().prepareStats(indexName).get().getTotal().getDocs().getCount();

Solution 3

Just an addition to @evanjd's answer

import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.action.search.SearchType;
import org.elasticsearch.index.query.QueryBuilders.*;

 SearchResponse response = client.prepareSearch("your_index_goes_here")
   .setTypes("YourTypeGoesHere")
   .setQuery(QueryBuilders.termQuery("some_field", "some_value"))
   .setSize(0) // Don't return any documents, we don't need them.
   .get();

 SearchHits hits = response.getHits();
 long hitsCount = hits.getTotalHits().value;

we need to add .value to get long value of total hits otherwise it will be a string value like "6 hits"

long hitsCount = hits.getTotalHits().value;

long hitsCount = hits.getTotalHits().value;

Solution 4

Breaking changes after 7.0; you need to set track_total_hits to true explicitly in the search request.

https://www.elastic.co/guide/en/elasticsearch/reference/current/breaking-changes-7.0.html#track-total-hits-10000-default

Solution 5

We can also get lowLevelClient from highLevelClient and invoke the "_count" rest API like "GET /twitter/_doc/_count?q=user:kimchy".

View more solutions

Comments

[14wml]

what is the type of client?

[evanjd]

@14wml TransportClient. See here: elastic.co/guide/en/elasticsearch/client/java-api/6.3/…

[ScottSummers]

You might also want to take a look at this stackoverflow.com/questions/35252156/…

[Matt Lachman]

This frequently gives me a result that differs from what I expect. I have an integration test that deletes an index, then recreates it and loads 20 docs. The count is always higher than I'm expecting using this method, and it's usually a multiple of 20.