OpenSearch/docs/reference/cat/segments.asciidoc

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[[cat-segments]]
== cat segments
The `segments` command provides low level information about the segments
in the shards of an index. It provides information similar to the
link:indices-segments.html[_segments] endpoint. For example:
[source,js]
--------------------------------------------------
GET /_cat/segments?v
--------------------------------------------------
// CONSOLE
// TEST[s/^/PUT \/test\/test\/1?refresh\n{"test":"test"}\nPUT \/test1\/test\/1?refresh\n{"test":"test"}\n/]
might look like:
["source","txt",subs="attributes,callouts"]
--------------------------------------------------
index shard prirep ip segment generation docs.count docs.deleted size size.memory committed searchable version compound
test 0 p 127.0.0.1 _0 0 1 0 3kb 2042 false true {lucene_version} true
test1 0 p 127.0.0.1 _0 0 1 0 3kb 2042 false true {lucene_version} true
--------------------------------------------------
// TESTRESPONSE[s/3kb/\\d+(\\.\\d+)?[mk]?b/ s/2042/\\d+/ non_json]
The output shows information about index names and shard numbers in the first
two columns.
If you only want to get information about segments in one particular index,
you can add the index name in the URL, for example `/_cat/segments/test`. Also,
several indexes can be queried like `/_cat/segments/test,test1`
The following columns provide additional monitoring information:
prirep:: Whether this segment belongs to a primary or replica shard.
ip:: The ip address of the segment's 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.