How to connect PolyBase to Google Data Catalog

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 Google Data Catalog, you get access to your Google Data Catalog data directly alongside your SQL Server data. This article describes creating an external data source and external tables to grant access to live Google Data Catalog 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 Google Data Catalog data using PolyBase due to optimized data processing built into the driver. When you issue complex SQL queries from SQL Server to Google Data Catalog, the driver pushes down supported SQL operations, like filters and aggregations, directly to Google Data Catalog 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 Google Data Catalog data, using a single query to pull data from distributed sources.

Connect to Google Data Catalog

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 Google Data Catalog Sys is created automatically).

Google Data Catalog uses the OAuth authentication standard. Authorize access to Google APIs on behalf on individual users or on behalf of users in a domain.

Before connecting, specify the following to identify the organization and project you would like to connect to:

• OrganizationId: The ID associated with the Google Cloud Platform organization resource you would like to connect to. Find this by navigating to the cloud console.

  Click the project selection drop-down, and select your organization from the list. Then, click More -> Settings. The organization ID is displayed on this page.

• ProjectId: The ID associated with the Google Cloud Platform project resource you would like to connect to.

  Find this by navigating to the cloud console dashboard and selecting your project from the Select from drop-down. The project ID will be present in the Project info card.

When you connect, the OAuth endpoint opens in your default browser. Log in and grant permissions to the application to completes the OAuth process. For more information, refer to the OAuth section in the Help documentation.

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

Create an External Data Source for Google Data Catalog 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 Google Data Catalog data.

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

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

Create an External Data Source for Google Data Catalog

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

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

For Google Data Catalog, 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_googledatacatalog_source
WITH ( 
  LOCATION = 'odbc://SERVER_URL',
  CONNECTION_OPTIONS = 'DSN=CData Google Data Catalog Sys',
  -- PUSHDOWN = ON | OFF,
  CREDENTIAL = googledatacatalog_creds
);

Create External Tables for Google Data Catalog

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

CREATE EXTERNAL TABLE Schemas(
  Type [nvarchar](255) NULL,
  DatasetName [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='Schemas',
  DATA_SOURCE=cdata_googledatacatalog_source
);

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