Counting matched results
It is often required to return only the count of the matched results and not the results themselves. The advantages of using a count request is the performance it offers and reduced resource usage, as a standard search call also returns hits count.
A lot of scenarios involve counting, as follows:
To return the number of, for example, posts for a blog or comments for a post.
To validate that some items are available. Are there posts? Are there comments?
Getting ready
You need a working ElasticSearch cluster and an index populated with the script chapter_05/populate_query.sh, available in the code bundle for this book.
How to do it...
In order to execute a counting query, perform the following steps:
From the command line, execute a count query:
curl -XGET 'http://127.0.0.1:9200/test-index/test-type/_count?pretty=true' -d '{"query":{"match_all":{}}}'The following result should be returned by ElasticSearch if everything works all right:
{ "count" : 3, "_shards" : { ...