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

# DuckDB

> Set up Cube with DuckDB for cloud object storage, local database files, or MotherDuck-backed hybrid query execution.

[DuckDB][duckdb] is an in-process SQL OLAP database management system, and has
support for querying data in CSV, JSON and Parquet formats from an AWS
S3-compatible blob storage. This means you can [query data stored in AWS S3,
Google Cloud Storage, or Cloudflare R2][duckdb-docs-s3-import].
You can also use the [`CUBEJS_DB_DUCKDB_DATABASE_PATH`](/reference/configuration/environment-variables#cubejs_db_duckdb_database_path) environment variable to
connect to a local DuckDB database.

<Frame>
  <img src="https://ucarecdn.com/d3e42677-83ce-4ad8-8ac9-c39d3b74e252/" />
</Frame>

Cube can also connect to [MotherDuck][motherduck], a cloud-based serverless
analytics platform built on DuckDB. When connected to MotherDuck, DuckDB uses
[hybrid execution][motherduck-docs-architecture] and routes queries to S3
through MotherDuck for better performance.

<Frame>
  <img src="https://ucarecdn.com/4fbb7247-379c-48a3-b298-0d87922e2531/" />
</Frame>

## Prerequisites

* A set of IAM credentials which allow access to the S3-compatible data source.
  Credentials are only required for private S3 buckets.
* The region of the bucket
* The name of a bucket to query data from

## Setup

### Manual

Add the following to a `.env` file in your Cube project:

```dotenv theme={"dark"}
CUBEJS_DB_TYPE=duckdb
```

### Cube Cloud

In Cube Cloud, select **DuckDB** when creating a new deployment
and fill in the required fields:

<Frame>
  <img src="https://ucarecdn.com/ffad02b1-a563-47e4-bbc0-0302ab046ccd/" alt="Cube Cloud DuckDB Configuration Screen" />
</Frame>

<Info>
  If you are not using MotherDuck, leave the **MotherDuck Token**
  field blank.
</Info>

<Info>
  You can also explore how DuckDB works with Cube if you create a [demo
  deployment][ref-demo-deployment] in Cube Cloud.
</Info>

## Environment Variables

| Environment Variable                                                                                                            | Description                                                                                                           | Possible Values                                               | Required |
| ------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------- | :------: |
| [`CUBEJS_DB_DUCKDB_MEMORY_LIMIT`](/reference/configuration/environment-variables#cubejs_db_duckdb_memory_limit)                 | The maximum memory limit for DuckDB. Equivalent to `SET memory_limit=<MEMORY_LIMIT>`. Default is 75% of available RAM | A valid memory limit                                          |     ❌    |
| [`CUBEJS_DB_DUCKDB_SCHEMA`](/reference/configuration/environment-variables#cubejs_db_duckdb_schema)                             | The [default search schema][link-duckdb-configuration-ref]                                                            | A valid schema name                                           |     ❌    |
| [`CUBEJS_DB_DUCKDB_MOTHERDUCK_TOKEN`](/reference/configuration/environment-variables#cubejs_db_duckdb_motherduck_token)         | The service token to use for connections to MotherDuck                                                                | A valid [MotherDuck service token][motherduck-docs-svc-token] |     ❌    |
| [`CUBEJS_DB_DUCKDB_DATABASE_PATH`](/reference/configuration/environment-variables#cubejs_db_duckdb_database_path)               | The database filepath to use for connection to a local database.                                                      | A valid duckdb database file path                             |     ❌    |
| `CUBEJS_DB_DUCKDB_S3_ACCESS_KEY_ID`                                                                                             | The Access Key ID to use for database connections                                                                     | A valid Access Key ID                                         |     ❌    |
| `CUBEJS_DB_DUCKDB_S3_SECRET_ACCESS_KEY`                                                                                         | The Secret Access Key to use for database connections                                                                 | A valid Secret Access Key                                     |     ❌    |
| `CUBEJS_DB_DUCKDB_S3_ENDPOINT`                                                                                                  | The S3 endpoint                                                                                                       | A valid [S3 endpoint][duckdb-docs-s3-import]                  |     ❌    |
| `CUBEJS_DB_DUCKDB_S3_REGION`                                                                                                    | The [region of the bucket][duckdb-docs-s3-import]                                                                     | A valid AWS region                                            |     ❌    |
| `CUBEJS_DB_DUCKDB_S3_USE_SSL`                                                                                                   | Use SSL for connection                                                                                                | A boolean                                                     |     ❌    |
| `CUBEJS_DB_DUCKDB_S3_URL_STYLE`                                                                                                 | To choose the S3 URL style(vhost or path)                                                                             | `vhost` or `path`                                             |     ❌    |
| `CUBEJS_DB_DUCKDB_S3_SESSION_TOKEN`                                                                                             | The token for the S3 session                                                                                          | A valid Session Token                                         |     ❌    |
| [`CUBEJS_DB_DUCKDB_EXTENSIONS`](/reference/configuration/environment-variables#cubejs_db_duckdb_extensions)                     | A comma-separated list of DuckDB extensions to install and load                                                       | A comma-separated list of DuckDB extensions                   |     ❌    |
| [`CUBEJS_DB_DUCKDB_COMMUNITY_EXTENSIONS`](/reference/configuration/environment-variables#cubejs_db_duckdb_community_extensions) | A comma-separated list of DuckDB community extensions to install and load                                             | A comma-separated list of DuckDB community extensions         |     ❌    |
| `CUBEJS_DB_DUCKDB_S3_USE_CREDENTIAL_CHAIN`                                                                                      | A flag to use credentials chain for secrets for S3 connections                                                        | `true`, `false`. Defaults to `false`                          |     ❌    |
| [`CUBEJS_CONCURRENCY`](/reference/configuration/environment-variables#cubejs_concurrency)                                       | The number of [concurrent queries][ref-data-source-concurrency] to the data source                                    | A valid number                                                |     ❌    |

[ref-data-source-concurrency]: /admin/connect-to-data/concurrency#data-source-concurrency

## Pre-Aggregation Feature Support

### count\_distinct\_approx

Measures of type
[`count_distinct_approx`][ref-schema-ref-types-formats-countdistinctapprox] can
be used in pre-aggregations when using DuckDB as a source database. To learn
more about DuckDB's support for approximate aggregate functions, [click
here][duckdb-docs-approx-agg-fns].

## Pre-Aggregation Build Strategies

<Info>
  To learn more about pre-aggregation build strategies, [head
  here][ref-caching-using-preaggs-build-strats].
</Info>

| Feature       | Works with read-only mode? | Is default? |
| ------------- | :------------------------: | :---------: |
| Batching      |              ❌             |      ✅      |
| Export Bucket |              -             |      -      |

By default, DuckDB uses a [batching][self-preaggs-batching] strategy to build
pre-aggregations.

### Batching

No extra configuration is required to configure batching for DuckDB.

### Export Bucket

DuckDB does not support export buckets.

## SSL

Cube does not require any additional configuration to enable SSL as DuckDB
connections are made over HTTPS.

[duckdb]: https://duckdb.org/

[duckdb-docs-approx-agg-fns]: https://duckdb.org/docs/sql/aggregates.html#approximate-aggregates

[duckdb-docs-s3-import]: https://duckdb.org/docs/guides/import/s3_import

[link-duckdb-configuration-ref]: https://duckdb.org/docs/sql/configuration.html#configuration-reference

[motherduck]: https://motherduck.com/

[motherduck-docs-architecture]: https://motherduck.com/docs/architecture-and-capabilities#hybrid-execution

[motherduck-docs-svc-token]: https://motherduck.com/docs/authenticating-to-motherduck/#authentication-using-a-service-token

[ref-caching-using-preaggs-build-strats]: /docs/pre-aggregations/using-pre-aggregations#pre-aggregation-build-strategies

[ref-schema-ref-types-formats-countdistinctapprox]: /reference/data-modeling/measures#type

[self-preaggs-batching]: #batching

[ref-demo-deployment]: /docs/deployment/cloud/deployments#demo-deployments