How to connect PolyBase to Exa

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 API Driver for ODBC, you get access to your Exa data directly alongside your SQL Server data. This article describes creating an external data source and external tables to grant access to live Exa data using T-SQL queries.

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

The CData ODBC drivers offer unmatched performance for interacting with live Exa data using PolyBase due to optimized data processing built into the driver. When you issue complex SQL queries from SQL Server to Exa, the driver pushes down supported SQL operations, like filters and aggregations, directly to Exa 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 Exa data, using a single query to pull data from distributed sources.

Connect to Exa

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 Exa Sys is created automatically).

Start by setting the Profile connection property to the location of the Exa Profile on disk (e.g. C:\profiles\Exa.apip). Next, set the ProfileSettings connection property to the connection string for Exa (see below).

Exa API Profile Settings

Visit dashboard.exa.ai, sign in or create an account, and generate an API key from your API settings.

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

Create an External Data Source for Exa 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 Exa data.

NOTE: Since Exa does not require a User or Password to authenticate, you may use whatever values you wish for IDENTITY and SECRET.

CREATE DATABASE SCOPED CREDENTIAL api_creds
WITH IDENTITY = 'username', SECRET = 'password';

Create an External Data Source for Exa

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

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

For Exa, set SERVERNAME to the URL or address for your server (e.g. 'localhost' or '127.0.0.1' for local servers; the remote URL for remote servers). Leave PORT empty. PUSHDOWN is set to ON by default, meaning the ODBC Driver can leverage server-side processing for complex queries.

CREATE EXTERNAL DATA SOURCE cdata_api_source
WITH ( 
  LOCATION = 'odbc://SERVER_URL',
  CONNECTION_OPTIONS = 'DSN=CData Exa Sys',
  -- PUSHDOWN = ON | OFF,
  CREDENTIAL = api_creds
);

Create External Tables for Exa

After creating the external data source, use CREATE EXTERNAL TABLE statements to link to Exa data from your SQL Server instance. The table column definitions must match those exposed by the CData API Driver for ODBC. 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 Exa Answer would look similar to the following:

CREATE EXTERNAL TABLE Answer(
  RequestId [nvarchar](255) NULL,
  Answer [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='Answer',
  DATA_SOURCE=cdata_api_source
);

Having created external tables for Exa 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 Exa, freeing up local resources and computing power. Download a free, 30-day trial of the ODBC Driver for Exa and start working with live Exa data alongside your SQL Server data today.