Run federated queries on Oracle

Preview

This article describes how to set up Lakehouse Federation to run federated queries on Oracle data that is not managed by Databricks. To learn more about Lakehouse Federation, see What is Lakehouse Federation?.

To connect to your Oracle database using Lakehouse Federation, you must create the following in your Databricks Unity Catalog metastore:

A connection to your Oracle database.
A foreign catalog that mirrors your Oracle database in Unity Catalog so that you can use Unity Catalog query syntax and data governance tools to manage Databricks user access to the database.

Before you begin

Before you begin, make sure you meet the requirements in this section.

Databricks requirements

Workspace requirements:

Workspace enabled for Unity Catalog.

Compute requirements:

Network connectivity from your compute resource to the target database systems. See Networking recommendations for Lakehouse Federation.
Databricks compute must use Databricks Runtime 16.1 or above and Shared or Single user access mode.
SQL warehouses must be pro or serverless and must use 2024.50 or above.

Permissions required:

To create a connection, you must be a metastore admin or a user with the CREATE CONNECTION privilege on the Unity Catalog metastore attached to the workspace.
To create a foreign catalog, you must have the CREATE CATALOG permission on the metastore and be either the owner of the connection or have the CREATE FOREIGN CATALOG privilege on the connection.

Additional permission requirements are specified in each task-based section that follows.

Oracle requirements

Server-side encryption enabled.

Create a Databricks connection

A connection specifies a path and credentials for accessing an external database system. To create a connection, you can use Catalog Explorer or the CREATE CONNECTION SQL command in a Databricks notebook or the Databricks SQL query editor.

Note

You can also use the Databricks REST API or the Databricks CLI to create a connection. See POST /api/2.1/unity-catalog/connections and Unity Catalog commands.

Permissions required: Metastore admin or user with the CREATE CONNECTION privilege.

In the Databricks workspace, click Catalog.
In the left pane, expand the External Data menu and select Connections.
Click Create connection.
Enter a user-friendly Connection name.
Select a Connection type of Oracle.
Enter the following connection properties for the Oracle instance:
- Host: For example, oracle-demo.123456.rds.amazonaws.com
- Port: For example, 1521
- User: For example, oracle_user
- Password: For example, password123
(Optional) Add a comment.
Click Create.

Run the following command in a notebook or the Databricks SQL query editor:

CREATE CONNECTION <connection-name> TYPE oracle
OPTIONS (
  host '<hostname>',
  port '<port>',
  user '<user>',
  password '<password>'
);

Databricks recommends that you use Databricks secrets instead of plaintext strings for sensitive values like credentials. For example:

CREATE CONNECTION <connection-name> TYPE oracle
OPTIONS (
  host '<hostname>',
  port '<port>',
  user secret ('<secret-scope>','<secret-key-user>'),
  password secret ('<secret-scope>','<secret-key-password>')
)

If you must use plaintext strings in notebook SQL commands, avoid truncating the string by escaping special characters like $ with \. For example: \$.

For information about setting up secrets, see Secret management.

Create a foreign catalog

A foreign catalog mirrors a database in an external data system so that you can query and manage access to data in that database using Databricks and Unity Catalog. To create a foreign catalog, you use a connection to the data source that has already been defined.

To create a foreign catalog, you can use Catalog Explorer or the CREATE FOREIGN CATALOG SQL command in a Databricks notebook or the SQL query editor.

Note

You can also use the Databricks REST API or the Databricks CLI to create a catalog. See POST /api/2.1/unity-catalog/catalogs and Unity Catalog commands.

Permissions required: CREATE CATALOG permission on the metastore and either ownership of the connection or the CREATE FOREIGN CATALOG privilege on the connection.

In the Databricks workspace, click Catalog to open Catalog Explorer.
At the top of the Catalog pane, click the Add icon and select Add a catalog from the menu.

Alternatively, from the Quick access page, click the Catalogs button, and then click the Create catalog button.
Follow the instructions for creating foreign catalogs in Create catalogs.

Run the following SQL command in a notebook or SQL query editor. Items in brackets are optional. Replace the placeholder values:

<catalog-name>: Name for the catalog in Databricks.
<connection-name>: The connection object that specifies the data source, path, and access credentials.
<service-name>: Service name you want to mirror as a catalog in Databricks.

CREATE FOREIGN CATALOG [IF NOT EXISTS] <catalog-name> USING CONNECTION <connection-name>
OPTIONS (service_name '<service-name>');

Supported pushdowns

The following pushdowns are supported:

Filters
Projections
Limit
Aggregates
Offset
Cast
Contains, Startswith, Endswith

Data type mappings

When you read from Oracle to Spark, data types map as follows:

Oracle type	Spark type
TIMESTAMP WITH TIMEZONE, TIMESTAMP WITH LOCAL TIMEZONE	TimestampType
DATE, TIMESTAMP	TimestampType/TimestampNTZType*
NUMBER, FLOAT	DecimalType
BINARY FLOAT	FloatType
BINARY DOUBLE	DoubleType
CHAR, NCHAR, VARCHAR2, NVARCHAR2	StringType

* DATE and TIMESTAMP are mapped to Spark TimestampType if spark.sql.timestampType = TIMESTAMP_LTZ (default). They are mapped to TimestampNTZType if spark.sql.timestampType = TIMESTAMP_NTZ.