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

Getting Started

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Configure Presto Connectivity for PolyBase

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

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

2. Select "Presto" from the Add Connection panel
👁 Selecting a data source

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

   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.
   👁 Configuring a connection (Salesforce is shown)
   
4. Click Save & Test
5. Navigate to the Permissions tab in the Add Presto Connection page and update the User-based permissions. 👁 Updating 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. 👁 Creating a new PAT
   
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 Presto data from Polybase.

Create an External Data Source for Presto 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 Presto 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 Presto

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

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

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 CData Connect AI. You can use the Data Explorer in Connect AI to see the table definition.

👁 Table definition in the Data Explorer (Salesforce is shown)

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 Presto Customer would look similar to the following.

CREATE EXTERNAL TABLE Customer(
 FirstName COLLATE [nvarchar](255) NULL,
 LastName COLLATE [nvarchar](255) NULL,
 ...
) WITH ( 
 LOCATION='Presto1.Presto.Customer',
 DATA_SOURCE=ConnectCloudInstance
);

Having created external tables for Presto 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!