Using ForceMerge on an index

The Elasticsearch core is based on Lucene, which stores data in segments on disk. During the life of an index, a lot of segments are created and changed. Since many other NoSQL systems (such as Cassandra, Accumulo, and HBase) prevent segments and part of the data from being rewritten, the records are not deleted in place, but they are put in a tombstone state. This means that the document is marked and deleted in metadata without the data being changed on disk. With the increasing number of segments, the speed of searching is decreased due to the time required to read all of them or skipping the records that aren't live (tombstones). The ForceMerge operation allows us to consolidate the index for quicker searching performance and reducing segments.

Getting ready

You will need an up-and-running Elasticsearch installation, as we described in the Downloading and installing Elasticsearch recipe of Chapter 1, Getting Started.

To execute the commands...