The optimize API allows to optimize one or more indices through an API. The optimize process basically optimizes the index for faster search operations (and relates to the number of segments a lucene index within each shard). The optimize operation allows to optimize the number of segments to optimize to.
$ curl -XPOST 'http://localhost:9200/twitter/_optimize'
The optimize API accepts the following request parameters:
| Name | Description |
|---|---|
| max_num_segments | The number of segments to optimize to. To fully optimize the index, set it to 1. Defaults to simply checking if a merge needs to execute, and if so, executes it. |
| only_expunge_deletes | Should the optimize process only expunge segments with deletes in it. In Lucene, a document is not deleted from a segment, just marked as deleted. During a merge process of segments, a new segment is created that does have those deletes. This flag allow to only merge segments that have deletes. Defaults to false. |
| refresh | Should a refresh be performed after the optimize. Defaults to true. |
| flush | Should a flush be performed after the optimize. Defaults to true. |
| wait_for_merge | Should the request wait for the merge to end. Defaults to true. Note, a merge can potentially be a very heavy operation, so it might make sense to run it set to false. |
The optimize API can be applied to more than one index with a single call, or even on _all the indices.
$ curl -XPOST 'http://localhost:9200/kimchy,elasticsearch/_optimize'
$ curl -XPOST 'http://localhost:9200/_optimize'