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Connect to Presto as an External Data Source using PolyBase

Use the CData ODBC Driver for Presto and PolyBase to create an external data source in SQL Server 2019 with access to live Presto data.

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 Presto, you get access to your Presto data directly alongside your SQL Server data. This article walks through creating an external data source and external tables to grant access to live Presto data using T-SQL queries.

The CData ODBC drivers offer unmatched performance for interacting with live Presto data using PolyBase due to optimized data processing built into the driver. When you issue complex SQL queries from SQL Server to Presto, the driver pushes down supported SQL operations, like filters and aggregations, directly to Presto 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 Presto data, using a single query to pull data from distributed sources.

Connect to Presto

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 Presto Sys is created automatically).

Set the Server and Port connection properties to connect, in addition to any authentication properties that may be required.

To enable TLS/SSL, set UseSSL to true.

Authenticating with LDAP

In order to authenticate with LDAP, set the following connection properties:

  • AuthScheme: Set this to LDAP.
  • User: The username being authenticated with in LDAP.
  • Password: The password associated with the User you are authenticating against LDAP with.

Authenticating with Kerberos

In order to authenticate with KERBEROS, set the following connection properties:

  • AuthScheme: Set this to KERBEROS.
  • KerberosKDC: The Kerberos Key Distribution Center (KDC) service used to authenticate the user.
  • KerberosRealm: The Kerberos Realm used to authenticate the user with.
  • KerberosSPN: The Service Principal Name for the Kerberos Domain Controller.
  • KerberosKeytabFile: The Keytab file containing your pairs of Kerberos principals and encrypted keys.
  • User: The user who is authenticating to Kerberos.
  • Password: The password used to authenticate to Kerberos.

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

Create an External Data Source for Presto 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 Presto data.

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

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

Create an External Data Source for Presto

Execute the following SQL command to create an external data source for Presto with PolyBase, using the DSN and credentials configured earlier.

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

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

Create External Tables for Presto

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

CREATE EXTERNAL TABLE Customer(
  FirstName [nvarchar](255) NULL,
  LastName [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='Customer',
  DATA_SOURCE=cdata_presto_source
);

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