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

# clickhouseTarget

> Configure a ClickHouse target for Solana Pipes SDK.

See the [ClickHouse guide](../../../guides/basic-development/targets/clickhouse) for usage examples, table design, and setup instructions.

```ts theme={"system"}
import { clickhouseTarget } from '@subsquid/pipes/targets/clickhouse'
```

## `clickhouseTarget`

```ts theme={"system"}
clickhouseTarget<T>({
  client: ClickHouseClient,
  onStart?: (ctx: { store: ClickhouseStore; logger: Logger }) => unknown | Promise<unknown>,
  onData: (ctx: { store: ClickhouseStore; data: T; ctx: HookContext }) => unknown | Promise<unknown>,
  onRollback?: (ctx: {
    reason: 'recovery' | 'fork'
    store: ClickhouseStore
    safeCursor: BlockCursor
  }) => unknown | Promise<unknown>,
  settings?: ClickhouseSettings,
})
```

| Parameter    | Required | Description                                                                                                 |
| ------------ | -------- | ----------------------------------------------------------------------------------------------------------- |
| `client`     | Yes      | Client from `@clickhouse/client`.                                                                           |
| `onStart`    | No       | Runs once before processing starts. Use for table creation or other setup.                                  |
| `onData`     | Yes      | Called for each batch.                                                                                      |
| `onRollback` | No       | Called on every restart with a persisted cursor (`reason: 'recovery'`) and on each fork (`reason: 'fork'`). |
| `settings`   | No       | Configuration for the internal cursor state table. See `ClickhouseSettings` below.                          |

**`ClickhouseSettings`:**

| Field      | Default                      | Description                                                                                                                                                                                                                         |
| ---------- | ---------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `database` | Client's configured database | ClickHouse database for the state table.                                                                                                                                                                                            |
| `table`    | `'sync'`                     | Name of the state table.                                                                                                                                                                                                            |
| `id`       | Pipe's source `id`           | Stream identifier within the state table. An explicit value always wins; otherwise the pipe's source `id` is used. Cursors stored under the legacy `'stream'` key by older SDK versions are migrated automatically on first resume. |
| `maxRows`  | `10000`                      | Maximum rows retained per stream id in the state table.                                                                                                                                                                             |

## `ClickhouseStore` methods

| Method                                                  | Description                                                                                                                                                                                                                                                                                                                                                       |
| ------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `store.insert(params)`                                  | Queues an insert. Non-blocking — returns a `Promise` but need not be awaited inside `onData`; inserts are flushed when the target closes.                                                                                                                                                                                                                         |
| `store.query(params)`                                   | Passthrough to `client.query()`.                                                                                                                                                                                                                                                                                                                                  |
| `store.command(params)`                                 | Passthrough to `client.command()`.                                                                                                                                                                                                                                                                                                                                |
| `store.removeAllRows({ tables, where, params? })`       | Removes rows matching `where`. Engine-aware: on `CollapsingMergeTree`-family tables with a `sign` column it inserts cancel rows (`sign = -1`) — the only mechanism that propagates through materialized views; on any other engine it falls back to a lightweight `DELETE` with a logged warning (requires ClickHouse ≥ 23.3); `Distributed` tables are rejected. |
| `store.ensureRollbackIndex({ table, column? })`         | Eagerly creates the minmax skip index (default column `block_number`) that rollbacks otherwise create on first use. Call in `onStart` for existing large tables to avoid a slow first rollback.                                                                                                                                                                   |
| `store.removeAllRowsByQuery({ table, query, params? })` | Like `removeAllRows`, but uses a custom `SELECT` to identify the rows to cancel.                                                                                                                                                                                                                                                                                  |
| `store.executeFiles(dir)`                               | Executes all `.sql` files found in `dir`.                                                                                                                                                                                                                                                                                                                         |


## Related topics

- [clickhouseTarget](/en/sdk/pipes-sdk/evm/reference/basic-components/target/clickhouse.md)
- [ClickHouse](/en/sdk/pipes-sdk/solana/guides/basic-development/targets/clickhouse.md)
- [A prod-ready pipe](/en/sdk/pipes-sdk/solana/prod-ready-pipe.md)
- [Cursor management](/en/sdk/pipes-sdk/solana/guides/architecture-deep-dives/cursor-management.md)
- [Migrate to 1.0](/en/sdk/pipes-sdk/solana/migration.md)