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Flush API

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Flush API

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Flushes one or more data streams or indices.

response = client.indices.flush(
  index: 'my-index-000001'
)
puts response

POST /my-index-000001/_flush

Request

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POST /<target>/_flush

GET /<target>/_flush

POST /_flush

GET /_flush

Prerequisites

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

Description

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Flushing a data stream or index is the process of making sure that any data that is currently only stored in the transaction log is also permanently stored in the Lucene index. When restarting, Elasticsearch replays any unflushed operations from the transaction log in to the Lucene index to bring it back into the state that it was in before the restart. Elasticsearch automatically triggers flushes as needed, using heuristics that trade off the size of the unflushed transaction log against the cost of performing each flush.

Once each operation has been flushed it is permanently stored in the Lucene index. This may mean that there is no need to maintain an additional copy of it in the transaction log. The transaction log is made up of multiple files, called generations, and Elasticsearch will delete any generation files once they are no longer needed, freeing up disk space.

It is also possible to trigger a flush on one or more indices using the flush API, although it is rare for users to need to call this API directly. If you call the flush API after indexing some documents then a successful response indicates that Elasticsearch has flushed all the documents that were indexed before the flush API was called.

Path parameters

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<target>: (Optional, string) Comma-separated list of data streams, indices, and aliases to flush. Supports wildcards (*). To flush 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.

force

(Optional, Boolean) If true, the request forces a flush even if there are no changes to commit to the index. Defaults to false.

You can use this parameter to increment the generation number of the transaction log.

This parameter is considered internal.

ignore_unavailable

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

wait_if_ongoing

(Optional, Boolean) If true, the flush operation blocks until execution when another flush operation is running.

If false, Elasticsearch returns an error if you request a flush when another flush operation is running.

Defaults to true.

Examples

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Flush a specific data stream or index

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response = client.indices.flush(
  index: 'my-index-000001'
)
puts response

POST /my-index-000001/_flush

Flush several data streams and indices

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response = client.indices.flush(
  index: 'my-index-000001,my-index-000002'
)
puts response

POST /my-index-000001,my-index-000002/_flush

Flush all data streams and indices in a cluster

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response = client.indices.flush
puts response

POST /_flush

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