Connect to Cosmos DB Data as an External Data Source using PolyBase

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 Cosmos DB, you get access to your Cosmos DB data directly alongside your SQL Server data. This article describes creating an external data source and external tables to grant access to live Cosmos DB data using T-SQL queries.

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

CData Connect AI provides a pure SQL Server interface for Cosmos DB, allowing you to query data from Cosmos DB without replicating the data to a natively supported database. Using optimized data processing out of the box, CData Connect AI pushes all supported SQL operations (filters, JOINs, etc.) directly to Cosmos DB, leveraging server-side processing to return the requested Cosmos DB data quickly.

Configure Cosmos DB Connectivity for PolyBase

Connectivity to Cosmos DB from PolyBase is made possible through CData Connect AI. To work with Cosmos DB data from PolyBase, we start by creating and configuring a Cosmos DB connection.

1. Log into Connect AI, click Sources, and then click Add Connection
👁 Adding a Connection

2. Select "Cosmos DB" from the Add Connection panel
👁 Selecting a data source

3. Enter the necessary authentication properties to connect to Cosmos DB.

   To obtain the connection string needed to connect to a Cosmos DB account using the SQL API, log in to the Azure Portal, select Azure Cosmos DB, and select your account. In the Settings section, click Connection String and set the following values:

   • AccountEndpoint: The Cosmos DB account URL from the Keys blade of the Cosmos DB account
   • AccountKey: In the Azure portal, navigate to the Cosmos DB service and select your Azure Cosmos DB account. From the resource menu, go to the Keys page. Find the PRIMARY KEY value and set AccountKey to this value.
   👁 Configuring a connection (Salesforce is shown)
   
4. Click Save & Test
5. Navigate to the Permissions tab in the Add Cosmos DB Connection page and update the User-based permissions. 👁 Updating permissions
   

Add a Personal Access Token

When connecting to Connect AI through the REST API, the OData API, or the Virtual SQL Server, a Personal Access Token (PAT) is used to authenticate the connection to Connect AI. It is best practice to create a separate PAT for each service to maintain granularity of access.

1. Click on the Gear icon () at the top right of the Connect AI app to open the settings page.
2. On the Settings page, go to the Access Tokens section and click Create PAT.
3. Give the PAT a name and click Create. 👁 Creating a new PAT
   
4. The personal access token is only visible at creation, so be sure to copy it and store it securely for future use.

With the connection configured and a PAT generated, you are ready to connect to Cosmos DB data from Polybase.

Create an External Data Source for Cosmos DB Data

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

Creating a Credential Database

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

NOTE: Set IDENTITY to your Connect AI username and set SECRET to your Personal Access Token.

CREATE DATABASE SCOPED CREDENTIAL ConnectCloudCredentials
WITH IDENTITY = 'yourusername', SECRET = 'yourPAT';

Create an External Data Source for Cosmos DB

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

CREATE EXTERNAL DATA SOURCE ConnectCloudInstance
WITH ( 
 LOCATION = 'sqlserver://tds.cdata.com:14333',
 PUSHDOWN = ON,
 CREDENTIAL = ConnectCloudCredentials
);

Create External Tables for Cosmos DB

After creating the external data source, use CREATE EXTERNAL TABLE statements to link to Cosmos DB data from your SQL Server instance. The table column definitions must match those exposed by CData Connect AI. You can use the Data Explorer in Connect AI to see the table definition.

👁 Table definition in the Data Explorer (Salesforce is shown)

Sample CREATE TABLE Statement

Execute a CREATE EXTERNAL TABLE SQL command to create the external table(s), using the collation and setting the LOCATION to three-part notation for the connection, catalog, and table. The statement to create an external table based on a Cosmos DB Customers would look similar to the following.

CREATE EXTERNAL TABLE Customers(
 City COLLATE [nvarchar](255) NULL,
 CompanyName COLLATE [nvarchar](255) NULL,
 ...
) WITH ( 
 LOCATION='CosmosDB1.CosmosDB.Customers',
 DATA_SOURCE=ConnectCloudInstance
);

Having created external tables for Cosmos DB in your SQL Server instance, you are now able to query local and remote data simultaneously. To get live data access to hundreds of SaaS, Big Data, and NoSQL sources directly from your SQL Server database, try CData Connect AI today!