Index segments API
editIndex segments API
editReturns 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
Prerequisites
edit-
If the Elasticsearch security features are enabled, you must have the
monitorormanageindex privilege for the target data stream, index, or index alias.
Path parameters
edit-
<target> -
(Optional, string) Comma-separated list of data streams, indices, and index aliases used to limit the request. Wildcard expressions (
*) are supported.To target all data streams and indices in a cluster, omit this parameter or use
_allor*.
Query parameters
edit-
allow_no_indices -
(Optional, Boolean) If
false, the request returns an error if any wildcard expression, index alias, or_allvalue targets only missing or closed indices. This behavior applies even if the request targets other open indices. For example, a request targetingfoo*,bar*returns an error if an index starts withfoobut no index starts withbar.Defaults to
true. -
expand_wildcards -
(Optional, string) Type of index that wildcard expressions 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 expressions 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 tofalse. -
verbose -
[preview]
This functionality is in technical preview and may be changed or removed in a future release. Elastic will work to fix any issues, but features in technical preview are not subject to the support SLA of official GA features.
(Optional, Boolean)
If
true, the response includes detailed information about Lucene’s memory usage. Defaults tofalse.
Response body
edit-
<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. Generation number, such as0. 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. -
memory_in_bytes -
(Integer) Bytes of segment data stored in memory for efficient search, such as
1264.A value of
-1indicates Elasticsearch was unable to compute this number. -
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
editGet segment information for a specific data stream or index
editGET /test/_segments
Get segment information for several data streams and indices
editGET /test1,test2/_segments
Get segment information for all data streams and indices in a cluster
editGET /_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,
"memory_in_bytes": 1410,
"committed": false,
"search": true,
"version": "7.0.0",
"compound": true,
"attributes": {
}
}
}
}
]
}
}
}
}
Verbose mode
editTo add additional information that can be used for debugging,
use the verbose flag.
This functionality is in technical preview and may be changed or removed in a future release. Elastic will work to fix any issues, but features in technical preview are not subject to the support SLA of official GA features.
GET /test/_segments?verbose=true
The API returns the following response:
{
...
"_0": {
...
"ram_tree": [
{
"description": "postings [PerFieldPostings(format=1)]",
"size_in_bytes": 2696,
"children": [
{
"description": "format 'Lucene50_0' ...",
"size_in_bytes": 2608,
"children" :[ ... ]
},
...
]
},
...
]
}
...
}