How to connect PolyBase to FTP

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

Connect to FTP

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 FTP Sys is created automatically).

To connect to FTP or SFTP servers, specify at least RemoteHost and FileProtocol. Specify the port with RemotePort.

Set User and Password to perform Basic authentication. Set SSHAuthMode to use SSH authentication. See the Getting Started section of the data provider help documentation for more information on authenticating via SSH.

Set SSLMode and SSLServerCert to secure connections with SSL.

The data provider lists the tables based on the available folders in your FTP server. 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 folders to list as views.
• FileRetrievalDepth: Set this to retrieve and list files recursively from the root table.

Stored Procedures are available to download files, upload files, and send protocol commands. See the Data Model chapter of the FTP data provider documentation for more information.

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

Create an External Data Source for FTP 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 FTP data.

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

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

Create an External Data Source for FTP

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

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

For FTP, 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_ftp_source
WITH ( 
  LOCATION = 'odbc://SERVER_URL',
  CONNECTION_OPTIONS = 'DSN=CData FTP Sys',
  -- PUSHDOWN = ON | OFF,
  CREDENTIAL = ftp_creds
);

Create External Tables for FTP

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

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

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