> ## Documentation Index
> Fetch the complete documentation index at: https://docs.risingwave.com/llms.txt
> Use this file to discover all available pages before exploring further.

# FLUSH

> The `FLUSH` command commits any pending data changes and forces RisingWave to persist updated data to storage, which guarantees subsequent reads can access the latest data.

## Syntax

```bash theme={null}
FLUSH;
```

## Purpose of `FLUSH`

RisingWave uses a snapshot-based mechanism for data durability. Periodically, a snapshot is triggered which flushes operator state to storage like S3. If a failure occurs, operators recover from the latest snapshot.

However, snapshots are asynchronous. By default, RisingWave does not guarantee read-after-write consistency — a write may not be visible to subsequent reads immediately.

The `FLUSH` command provides a way to synchronously persist pending changes and ensure subsequent reads reflect the latest data. It blocks until the changes are durable.

## When to use `FLUSH`

`FLUSH` should be used after any statements that change data, including:

* DML like `INSERT`, `UPDATE`, or `DELETE`.
* DDL creating objects that query the data.

In the example below, `FLUSH` ensures the pending data changes from the `INSERT` are persisted, and the new materialized view has been populated before querying it:

```sql theme={null}
CREATE TABLE users (id INT, name VARCHAR(50));

INSERT INTO users VALUES (1, 'Alice');

FLUSH;

CREATE MATERIALIZED VIEW user_count AS
  SELECT COUNT(*) AS total_users FROM users;

FLUSH;

SELECT * FROM user_count;
```