---
type: api
title: Flush data streams or indices
description: **All methods and paths for this operation:**
url: https://www.elastic.co/elastic/docs-builder/docs/4371/api/doc/elasticsearch/v9/operation/operation-indices-flush
resource: https://www.elastic.co/elastic/docs-builder/docs/4371/api/doc/elasticsearch/v9/operation/operation-indices-flush
products:
  - Elasticsearch
---

# Flush data streams or indices


Availability:

## Paths

- `POST` (also `GET`) `/{index}/_flush`
- `POST` (also `GET`) `/_flush`

- [Api key auth](/elastic/docs-builder/docs/4371/api/doc/elasticsearch/v9/authentication#apikeyauth)
- [Basic auth](/elastic/docs-builder/docs/4371/api/doc/elasticsearch/v9/authentication#basicauth)
- [Bearer auth](/elastic/docs-builder/docs/4371/api/doc/elasticsearch/v9/authentication#bearerauth)

#### Path Parameters

- `index` (union IndexName | [] IndexName) — optional, leave it out to use `/_flush`
  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`.

## Description

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 into 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.

After 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 when 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.

## Required authorization

* Index privileges: `maintenance`

## Query String Parameters

- `allow_no_indices` (boolean · default: true)
  A setting that does two separate checks on the index expression.
If `false`, the request returns an error (1) if any wildcard expression
(including `_all` and `*`) resolves to zero matching indices or (2) if the
complete set of resolved indices, aliases or data streams is empty after all
expressions are evaluated. If `true`, index expressions that resolve to no
indices are allowed and the request returns an empty result.
- `expand_wildcards` (string ExpandWildcards · default: open)
  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`.

Supported values include:
  - `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.
  Values: `all`, `open`, `closed`, `hidden`, `none`
- `force` (boolean · default: true)
  If `true`, the request forces a flush even if there are no changes to commit to the index.
- `ignore_unavailable` (boolean · default: false)
  If `false`, the request returns an error if it targets a concrete (non-wildcarded)
index, alias, or data stream that is missing, closed, or otherwise unavailable.
If `true`, unavailable concrete targets are silently ignored.
- `wait_if_ongoing` (boolean · default: true)
  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.

## Response

`application/json`

- `_shards` ({} ShardStatistics)
  - `failed` (number uint)
    The number of shards the operation or search attempted to run on but failed.
  - `successful` (number uint)
    The number of shards the operation or search succeeded on.
  - `total` (number uint)
    The number of shards the operation or search will run on overall.
  - `failures` ([] ShardFailure)
    - `index` (string IndexName)
    - `node` (string)
    - `reason` ({} ErrorCause)
      - `type` (string)
        The type of error
      - `reason` (union string) — nullable
        A human-readable explanation of the error, in English.
        One of: `string`
      - `stack_trace` (string)
        The server stack trace. Present only if the `error_trace=true` parameter was sent with the request.
      - `caused_by` ({} ErrorCause) — recursive
        Same fields as `reason` in `failures`
      - `root_cause` ([] ErrorCause) — recursive
        Same fields as `reason` in `failures`
      - `suppressed` ([] ErrorCause) — recursive
        Same fields as `reason` in `failures`
    - `shard` (number)
    - `status` (string)
    - `primary` (boolean)
  - `skipped` (number uint)
## Code Examples

#### Console

```console
POST /_flush
```

#### JavaScript

```javascript
const response = await client.indices.flush();
```

#### Python

```python
resp = client.indices.flush()
```

#### curl

```curl
curl -X POST "$ELASTICSEARCH_URL/_flush" \
  -H "Authorization: ApiKey $ELASTIC_API_KEY"
```

#### Java

```java
client.indices().flush(f -> f);
```

#### C#

```c#
var response = await client.Indices.FlushAsync();
```

#### PHP

```php
$resp = $client->indices()->flush();
```

#### Ruby

```ruby
response = client.indices.flush
```