How to connect PolyBase to Postmark

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

Connect to Postmark

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 Postmark Sys is created automatically).

Using API Key Authentication

Postmark uses server API tokens to authenticate requests. Each Postmark server has its own API token, which controls access to messages, bounces, templates, and statistics associated with that server.

To obtain your Server API Token, log in to your Postmark account and navigate to the server you want to connect to. Go to API Tokens under the server settings and copy the token labeled Server API token.

After setting the following connection properties, you are ready to connect:

• AuthScheme: Set this to APIKey.
• APIKey: Set this to your Postmark Server API Token. This value is sent as the X-Postmark-Server-Token header on every request.

Example connection string:

Profile=C:\profiles\Postmark.apip;AuthScheme=APIKey;ProfileSettings="APIKey=your-server-api-token"

Connecting to Postmark

Once the authentication is configured, you can connect to Postmark and query data from any of the available tables such as OutboundMessages, Bounces, and Templates.

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

Create an External Data Source for Postmark 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 Postmark data.

NOTE: Since Postmark 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 Postmark

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

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

For Postmark, 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 Postmark Sys',
  -- PUSHDOWN = ON | OFF,
  CREDENTIAL = api_creds
);

Create External Tables for Postmark

After creating the external data source, use CREATE EXTERNAL TABLE statements to link to Postmark 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 Postmark Bounces would look similar to the following:

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

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