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Elastic Docs ›Elasticsearch Guide [8.8] ›REST APIs ›Compact and aligned text (CAT) APIs

cat segments API

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cat segments API

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cat APIs are only intended for human consumption using the command line or Kibana console. They are not intended for use by applications. For application consumption, use the index segments API.

Returns low-level information about the Lucene segments in index shards, similar to the indices segments API.

For data streams, the API returns information about the stream’s backing indices.

Request

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GET /_cat/segments/<target>

GET /_cat/segments

Prerequisites

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  • If the Elasticsearch security features are enabled, you must have the monitor or manage cluster privilege to use this API. You must also have the monitor or manage index privilege for any data stream, index, or alias you retrieve.

Path parameters

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<target>
(Optional, string) Comma-separated list of data streams, indices, and aliases used to limit the request. Supports wildcards (*). To target all data streams and indices, omit this parameter or use * or _all.

Query parameters

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bytes
(Optional, byte size units) Unit used to display byte values.
format
(Optional, string) Short version of the HTTP accept header. Valid values include JSON, YAML, etc.
h

(Optional, string) Comma-separated list of column names to display.

If you do not specify which columns to include, the API returns the default columns in the order listed below. If you explicitly specify one or more columns, it only returns the specified columns.

Valid columns are:

index, i, idx
(Default) Name of the index.
shard, s, sh
(Default) Name of the shard.
prirep, p, pr, primaryOrReplica
(Default) Shard type. Returned values are primary or replica.
ip
(Default) IP address of the segment’s shard, such as 127.0.1.1.
segment
(Default) Name of the segment, such as _0. The segment name is derived from the segment generation and used internally to create file names in the directory of the shard.
generation
(Default) Generation number, such as 0. Elasticsearch increments this generation number for each segment written. Elasticsearch then uses this number to derive the segment name.
docs.count
(Default) The number of documents as reported by Lucene. This excludes deleted documents and counts any nested documents separately from their parents. It also excludes documents which were indexed recently and do not yet belong to a segment.
docs.deleted
(Default) The number of deleted documents as reported by Lucene, which may be higher or lower than the number of delete operations you have performed. This number excludes deletes that were performed recently and do not yet belong to a segment. Deleted documents are cleaned up by the automatic merge process if it makes sense to do so. Also, Elasticsearch creates extra deleted documents to internally track the recent history of operations on a shard.
size
(Default) Disk space used by the segment, such as 50kb.
size.memory

(Default) Bytes of segment data stored in memory for efficient search, such as 1264.

A value of -1 indicates Elasticsearch was unable to compute this number.

committed

(Default) If true, the segments is synced to disk. Segments that are synced can survive a hard reboot.

If 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

(Default) If true, the segment is searchable.

If false, the segment has most likely been written to disk but needs a refresh to be searchable.

version
(Default) Version of Lucene used to write the segment.
compound
(Default) If true, the segment is stored in a compound file. This means Lucene merged all files from the segment in a single file to save file descriptors.
id
ID of the node, such as k0zy.
help
(Optional, Boolean) If true, the response includes help information. Defaults to false.
s
(Optional, string) Comma-separated list of column names or column aliases used to sort the response.
v
(Optional, Boolean) If true, the response includes column headings. Defaults to false.

Examples

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response = client.cat.segments(
  v: true
)
puts response
GET /_cat/segments?v=true

The API returns the following response:

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           0 false     true       9.6.0   true
test1 0     p      127.0.0.1 _0               0          1            0  3kb           0 false     true       9.6.0   true
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