[[indices-optimize]]
== Optimize

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 holds
within each shard). The optimize operation allows to reduce the number
of segments by merging them.

[source,js]
--------------------------------------------------
$ curl -XPOST 'http://localhost:9200/twitter/_optimize'
--------------------------------------------------

[float]
[[optimize-parameters]]
=== Request Parameters

The optimize API accepts the following request parameters:

[horizontal]
`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 not have those deletes. This flag allows to only merge segments that have
deletes. Defaults to `false`.  Note that this won't override the
`index.merge.policy.expunge_deletes_allowed` threshold.

`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`.

[float]
[[optimize-multi-index]]
=== Multi Index

The optimize API can be applied to more than one index with a single
call, or even on `_all` the indices.

[source,js]
--------------------------------------------------
$ curl -XPOST 'http://localhost:9200/kimchy,elasticsearch/_optimize'

$ curl -XPOST 'http://localhost:9200/_optimize'
--------------------------------------------------