Connect to SFTP 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 SFTP, you get access to your SFTP data directly alongside your SQL Server data. This article describes creating an external data source and external tables to grant access to live SFTP 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 SFTP, allowing you to query data from SFTP 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 SFTP, leveraging server-side processing to return the requested SFTP data quickly.

Configure SFTP Connectivity for PolyBase

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

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

2. Select "SFTP" from the Add Connection panel

3. Enter the necessary authentication properties to connect to SFTP.

   SFTP can be used to transfer files to and from SFTP servers using the SFTP Protocol. To connect, specify the RemoteHost;. service uses the User and Password and public key authentication (SSHClientCert). Choose an SSHAuthMode and specify connection values based on your selection.

   Set the following connection properties to control the relational view of the file system:

   • RemotePath: Set this to the current working directory.
   • TableDepth: Set this to control the depth of subfolders to report as views.
   • FileRetrievalDepth: Set this to retrieve files recursively and list them in the Root table.
   Stored Procedures are available to download files, upload files, and send protocol commands. See gdatamodel for more on using SQL to interact with the server.
   
4. Click Save & Test
5. Navigate to the Permissions tab in the Add SFTP Connection page and update the User-based 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.
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 SFTP data from Polybase.

Create an External Data Source for SFTP 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 SFTP 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 SFTP

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

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

Create External Tables for SFTP

After creating the external data source, use CREATE EXTERNAL TABLE statements to link to SFTP 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.

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 SFTP MyDirectory would look similar to the following.

CREATE EXTERNAL TABLE MyDirectory(
  Filesize COLLATE [nvarchar](255) NULL,
  Filename COLLATE [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='SFTP1.SFTP.MyDirectory',
  DATA_SOURCE=ConnectCloudInstance
);

Having created external tables for SFTP 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!