How to connect PolyBase to HarperDB

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

Connect to HarperDB

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 HarperDB Sys is created automatically).

Set the Server, User, and Password connection properties to connect to HarperDB. Set UseSSL to secure connections with TLS/SSL.

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

Create an External Data Source for HarperDB 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 HarperDB data.

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

CREATE DATABASE SCOPED CREDENTIAL harperdb_creds
WITH IDENTITY = 'harperdb_username', SECRET = 'harperdb_password';

Create an External Data Source for HarperDB

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

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

PUSHDOWN is set to ON by default, meaning the ODBC Driver can leverage server-side processing for complex queries.

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

Create External Tables for HarperDB

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

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

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