How to connect PolyBase to Redshift

PolyBase for SQL Server allows you to query external data by using the same Transact-SQL syntax used to query a database table. When paired with the CData ODBC Driver for Amazon Redshift, you get access to your Redshift data directly alongside your SQL Server data. This article describes creating an external data source and external tables to grant access to live Redshift data using T-SQL queries.

NOTE: PolyBase is only available on SQL Server 19 and above, and only for Standard SQL Server.

The CData ODBC drivers offer unmatched performance for interacting with live Redshift data using PolyBase due to optimized data processing built into the driver. When you issue complex SQL queries from SQL Server to Redshift, the driver pushes down supported SQL operations, like filters and aggregations, directly to Redshift and utilizes the embedded SQL engine to process unsupported operations (often SQL functions and JOIN operations) client-side. And with PolyBase, you can also join SQL Server data with Redshift data, using a single query to pull data from distributed sources.

Connect to Redshift

If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs. To create an external data source in SQL Server using PolyBase, configure a System DSN (CData Redshift Sys is created automatically).

To connect to Redshift, set the following:

• Server: Set this to the host name or IP address of the cluster hosting the Database you want to connect to.
• Port: Set this to the port of the cluster.
• Database: Set this to the name of the database. Or, leave this blank to use the default database of the authenticated user.
• User: Set this to the username you want to use to authenticate to the Server.
• Password: Set this to the password you want to use to authenticate to the Server.

You can obtain the Server and Port values in the AWS Management Console:

1. Open the Amazon Redshift console (http://console.aws.amazon.com/redshift).
2. On the Clusters page, click the name of the cluster.
3. On the Configuration tab for the cluster, copy the cluster URL from the connection strings displayed.

Click "Test Connection" to ensure that the DSN is connected to Redshift properly. Navigate to the Tables tab to review the table definitions for Redshift.

Create an External Data Source for Redshift Data

After configuring the connection, you need to create a master encryption key and a credential database for the external data source.

Creating a Master Encryption Key

Execute the following SQL command to create a new master key, 'ENCRYPTION,' to encrypt the credentials for the external data source.

CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'password';

Creating a Credential Database

Execute the following SQL command to create credentials for the external data source connected to Redshift data.

NOTE: IDENTITY and SECRET correspond with the User and Password properties for Redshift.

CREATE DATABASE SCOPED CREDENTIAL redshift_creds
WITH IDENTITY = 'redshift_username', SECRET = 'redshift_password';

Create an External Data Source for Redshift

Execute a CREATE EXTERNAL DATA SOURCE SQL command to create an external data source for Redshift with PolyBase:

• Set the LOCATION parameter , using the DSN and credentials configured earlier.

NOTE: SERVERNAME and PORT corresponds to the Server and Port connection properties for Redshift. PUSHDOWN is set to ON by default, meaning the ODBC Driver can leverage server-side processing for complex queries.

CREATE EXTERNAL DATA SOURCE cdata_redshift_source
WITH ( 
  LOCATION = 'odbc://SERVERNAME[:PORT]',
  CONNECTION_OPTIONS = 'DSN=CData Redshift Sys',
  -- PUSHDOWN = ON | OFF,
  CREDENTIAL = redshift_creds
);

Create External Tables for Redshift

After creating the external data source, use CREATE EXTERNAL TABLE statements to link to Redshift data from your SQL Server instance. The table column definitions must match those exposed by the CData ODBC Driver for Amazon Redshift. You can refer to the Tables tab of the DSN Configuration Wizard to see the table definition.

Sample CREATE TABLE Statement

The statement to create an external table based on a Redshift Orders would look similar to the following:

CREATE EXTERNAL TABLE Orders(
  ShipName [nvarchar](255) NULL,
  ShipCity [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='Orders',
  DATA_SOURCE=cdata_redshift_source
);

Having created external tables for Redshift in your SQL Server instance, you are now able to query local and remote data simultaneously. Thanks to built-in query processing in the CData ODBC Driver, you know that as much query processing as possible is being pushed to Redshift, freeing up local resources and computing power. Download a free, 30-day trial of the ODBC Driver for Redshift and start working with live Redshift data alongside your SQL Server data today.