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Clear Cache API

Introduced 1.0

The clear cache API operation clears the caches of one or more indexes. For data streams, the API clears the caches of the stream’s backing indexes.

Endpoints

POST /_cache/clear
POST /{target}/_cache/clear

Path parameters

Parameter Data type Description
target String Comma-delimited list of data streams, indexes, and index aliases to which cache clearing is applied. Wildcard expressions (*) are supported. To target all data streams and indexes in a cluster, omit this parameter or use _all or *. Optional.

Query parameters

All query parameters are optional.

Parameter Data type Description
allow_no_indices Boolean Whether to ignore wildcards, index aliases, or _all target (target path parameter) values that don’t match any indexes. If false, the request returns an error if any wildcard expression, index alias, or _all target value doesn’t match any indexes. This behavior also applies if the request targets include other open indexes. For example, a request where the target is fig*,app* returns an error if an index starts with fig but no index starts with app. Default is true.
expand_wildcards String Determines the index types that wildcard expressions can expand to. Accepts multiple values separated by a comma, such as open,hidden. Valid values are:

all – Expand to open, closed, and hidden indexes.

open – Expand only to open indexes.

closed – Expand only to closed indexes

hidden – Expand to include hidden indexes. Must be combined with open or closed.

none – Expansions are not accepted.

Default is open. Caches of closed indexes cannot be cleared, so a request using closed or all fails if a wildcard expression matches a closed index, unless ignore_unavailable is true.
fielddata Boolean If true, clears the fields cache. Use the fields parameter to clear specific fields’ caches. Default is false.
fields String Comma-delimited list of field names whose fielddata is cleared from the cache. If specified without other cache parameters, clears only the fielddata of the listed fields. Does not support objects or field aliases. Default is all fields.
file Boolean If true, clears the unused entries from the file cache on nodes with the Search role. Unless query or fielddata is also true or fields is specified, setting file to true also clears all index caches. Default is false.
index String Comma-delimited list of indexes whose caches are cleared. An alternative to the target path parameter for the POST /_cache/clear endpoint.
ignore_unavailable Boolean If true, OpenSearch ignores missing or closed indexes. Default is false.
query Boolean If true, clears the query cache. Default is false.
request Boolean If true, clears the request cache. Default is false.

If none of the fielddata, query, request, or fields parameters is specified, all caches are cleared. Setting fielddata or query to true clears only that cache. If request is the only cache parameter set to true and fields is not specified, all caches are cleared.

Field data entries are removed during the next cache cleanup, which runs at the interval specified by the indices.cache.cleanup_interval setting (default 1m). Until then, fielddata statistics can show the size before the cache was cleared.

Example requests

The following example requests show multiple clear cache API uses.

Clear a specific cache

The following request clears the fields cache only:

POST /my-index/_cache/clear?fielddata=true
response = client.indices.clear_cache(
  index = "my-index",
  params = { "fielddata": "true" }
)

The following request clears the query cache only:

POST /my-index/_cache/clear?query=true
response = client.indices.clear_cache(
  index = "my-index",
  params = { "query": "true" }
)

The following request clears the request cache only:

POST /my-index/_cache/clear?request=true
response = client.indices.clear_cache(
  index = "my-index",
  params = { "request": "true" }
)

Clear the cache for specific fields

The following request clears the fields caches of product_name and category:

POST /my-index/_cache/clear?fields=product_name,category
response = client.indices.clear_cache(
  index = "my-index",
  params = { "fields": "product_name,category" }
)

Clear caches for specific data streams or indexes

The following request clears the cache for two specific indexes:

POST /my-index,my-index2/_cache/clear
response = client.indices.clear_cache(
  index = "my-index,my-index2"
)

Clear caches for all data streams and indexes

The following request clears the cache for all data streams and indexes:

POST /_cache/clear
response = client.indices.clear_cache()

Clear unused entries from the cache on search-capable nodes

The following request clears unused entries from the file cache on nodes with the Search role:

POST /*/_cache/clear?file=true
response = client.indices.clear_cache(
  index = "*",
  params = { "file": "true" }
)

Example response

The POST /books,hockey/_cache/clear request returns the following fields:

{
  "_shards" : {
    "total" : 4,
    "successful" : 2,
    "failed" : 0
  }
}

Response body fields

The POST /books,hockey/_cache/clear request returns the following response fields:

Field Data type Description
_shards Object Shard information.

The _shards object contains the following fields.

Field Data type Description
total Integer Total number of shards.
successful Integer Number of index shards with caches successfully cleared.
failed Integer Number of index shards with caches that failed to clear.

Required permissions

If you use the Security plugin, make sure you have the appropriate permissions: indices:admin/cache/clear.

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