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Elastic Docs ›Elasticsearch Guide [8.7] ›REST APIs ›Index APIs

Index segments API

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Index segments API

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Returns low-level information about the Lucene segments in index shards. For data streams, the API returns information about the stream’s backing indices.

GET /my-index-000001/_segments

Request

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GET /<target>/_segments

GET /_segments

Prerequisites

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  • If the Elasticsearch security features are enabled, you must have the monitor or manage index privilege for the target data stream, index, or alias.

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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allow_no_indices

(Optional, Boolean) If false, the request returns an error if any wildcard expression, index alias, or _all value targets only missing or closed indices. This behavior applies even if the request targets other open indices. For example, a request targeting foo*,bar* returns an error if an index starts with foo but no index starts with bar.

Defaults to true.

expand_wildcards

(Optional, string) Type of index that wildcard patterns can match. If the request can target data streams, this argument determines whether wildcard expressions match hidden data streams. Supports comma-separated values, such as open,hidden. Valid values are:

all
Match any data stream or index, including hidden ones.
open
Match open, non-hidden indices. Also matches any non-hidden data stream.
closed
Match closed, non-hidden indices. Also matches any non-hidden data stream. Data streams cannot be closed.
hidden
Match hidden data streams and hidden indices. Must be combined with open, closed, or both.
none
Wildcard patterns are not accepted.

Defaults to open.

ignore_unavailable
(Optional, Boolean) If false, the request returns an error if it targets a missing or closed index. Defaults to false.

Response body

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<segment>
(String) 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
(Integer) Generation number, such as 0. Elasticsearch increments this generation number for each segment written. Elasticsearch then uses this number to derive the segment name.
num_docs
(Integer) 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.
deleted_docs
(Integer) 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_in_bytes
(Integer) Disk space used by the segment, such as 50kb.
committed

(Boolean) 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.

search

(Boolean) 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
(String) Version of Lucene used to write the segment.
compound
(Boolean) If true, Lucene merged all files from the segment into a single file to save file descriptors.
attributes
(Object) Contains information about whether high compression was enabled.

Examples

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Get segment information for a specific data stream or index

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response = client.indices.segments(
  index: 'test'
)
puts response
GET /test/_segments

Get segment information for several data streams and indices

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GET /test1,test2/_segments

Get segment information for all data streams and indices in a cluster

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response = client.indices.segments
puts response
GET /_segments

The API returns the following response:

{
  "_shards": ...
  "indices": {
    "test": {
      "shards": {
        "0": [
          {
            "routing": {
              "state": "STARTED",
              "primary": true,
              "node": "zDC_RorJQCao9xf9pg3Fvw"
            },
            "num_committed_segments": 0,
            "num_search_segments": 1,
            "segments": {
              "_0": {
                "generation": 0,
                "num_docs": 1,
                "deleted_docs": 0,
                "size_in_bytes": 3800,
                "committed": false,
                "search": true,
                "version": "7.0.0",
                "compound": true,
                "attributes": {
                }
              }
            }
          }
        ]
      }
    }
  }
}
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