How to connect PolyBase to LDAP

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

Connect to LDAP

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 LDAP Sys is created automatically).

To establish a connection, the following properties under the Authentication section must be provided:

• Valid User and Password credentials (e.g., Domain\BobF or cn=Bob F,ou=Employees,dc=Domain).
• Server information, including the IP or host name of the Server, as well as the Port.

• BaseDN: This will limit the scope of LDAP searches to the height of the distinguished name provided.

  Note: Specifying a narrow BaseDN may greatly increase performance; for example, cn=users,dc=domain will only return results contained within cn=users and its children.

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

Create an External Data Source for LDAP Objects

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 LDAP objects.

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

CREATE DATABASE SCOPED CREDENTIAL ldap_creds
WITH IDENTITY = 'ldap_username', SECRET = 'ldap_password';

Create an External Data Source for LDAP

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

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

NOTE: SERVERNAME and PORT corresponds to the Server and Port connection properties for LDAP. PUSHDOWN is set to ON by default, meaning the ODBC Driver can leverage server-side processing for complex queries.

CREATE EXTERNAL DATA SOURCE cdata_ldap_source
WITH ( 
  LOCATION = 'odbc://SERVERNAME[:PORT]',
  CONNECTION_OPTIONS = 'DSN=CData LDAP Sys',
  -- PUSHDOWN = ON | OFF,
  CREDENTIAL = ldap_creds
);

Create External Tables for LDAP

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

CREATE EXTERNAL TABLE User(
  Id [nvarchar](255) NULL,
  LogonCount [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='User',
  DATA_SOURCE=cdata_ldap_source
);

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