segments命令提供了在一个索引分片中关于 segment（段）更低级别的信息。它提供的信息与 _segments endpoint（端点）相似。
% curl 'http://localhost:9200/_cat/segments?v'
index shard prirep ip segment generation docs.count [...]
test 4 p 192.168.2.105 _0 0 1
test1 2 p 192.168.2.105 _0 0 1
test1 3 p 192.168.2.105 _2 2 1
[...] docs.deleted size size.memory committed searchable version compound
0 2.9kb 7818 false true 4.10.2 true
0 2.9kb 7818 false true 4.10.2 true
0 2.9kb 7818 false true 4.10.2 true
在前两列的输出信息中展示了索引名和分配数量。
如果你只希望在一个指定的索引中获取关于 segment 的信息，你可以在 URL 中添加索引名，例如，/_cat/segments/test。当然，也可以像 /_cat/segments/test,test1 这样查询多个索引。
下面的列提供了额外的监控信息 :
| Column（列） | Description（描述） |
|---|---|
| prirep | Whether this segment belongs to a primary or replica shard. |
| ip | The ip address of the segments shard. |
| segment | A segment name, derived from the segment generation. The name is internally used to generate the file names in the directory of the shard this segment belongs to. |
| generation | The generation number is incremented with each segment that is written. The name of the segment is derived from this generation number. |
| docs.count | The number of non-deleted documents that are stored in this segment. Note that these are Lucene documents, so the count will include hidden documents (e.g. from nested types). |
| docs.deleted | The number of deleted documents that are stored in this segment. It is perfectly fine if this number is greater than 0, space is going to be reclaimed when this segment gets merged. |
| size | The amount of disk space that this segment uses. |
| size.memory | Segments store some data into memory in order to be searchable efficiently. This column shows the number of bytes in memory that are used. |
| committed | Whether the segment has been sync’ed on disk. Segments that are committed would survive a hard reboot. No need to worry in case of false, the data from uncommitted segments is also stored in the transaction log so that Elasticsearch is able to replay changes on the next start. |
| searchable | True if the segment is searchable. A value of false would most likely mean that the segment has been written to disk but no refresh occurred since then to make it searchable. |
| version | The version of Lucene that has been used to write this segment. |
| compound | Whether the segment is stored in a compound file. When true, this means that Lucene merged all files from the segment in a single one in order to save file descriptors. |