How to connect PolyBase to Greenhouse

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

Connect to Greenhouse

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 Greenhouse Sys is created automatically).

You need an API key to connect to Greenhouse. To create an API key, follow the steps below:

1. Click the Configure icon in the navigation bar and locate Dev Center on the left.
2. Select API Credential Management.
3. Click Create New API Key.
• Set "API Type" to Harvest.
• Set "Partner" to custom.
• Optionally, provide a description.
4. Proceed to Manage permissions and select the appropriate permissions based on the resources you want to access through the driver.
5. Copy the created key and set APIKey to that value.

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

Create an External Data Source for Greenhouse 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 Greenhouse data.

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

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

Create an External Data Source for Greenhouse

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

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

For Greenhouse, 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_greenhouse_source
WITH ( 
  LOCATION = 'odbc://SERVER_URL',
  CONNECTION_OPTIONS = 'DSN=CData Greenhouse Sys',
  -- PUSHDOWN = ON | OFF,
  CREDENTIAL = greenhouse_creds
);

Create External Tables for Greenhouse

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

CREATE EXTERNAL TABLE Applications(
  Id [nvarchar](255) NULL,
  CandidateId [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='Applications',
  DATA_SOURCE=cdata_greenhouse_source
);

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