How to connect PolyBase to Elasticsearch

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

Connect to Elasticsearch

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 Elasticsearch Sys is created automatically).

Set the Server and Port connection properties to connect. To authenticate, set the User and Password properties, PKI (public key infrastructure) properties, or both. To use PKI, set the SSLClientCert, SSLClientCertType, SSLClientCertSubject, and SSLClientCertPassword properties.

The data provider uses X-Pack Security for TLS/SSL and authentication. To connect over TLS/SSL, prefix the Server value with 'https://'. Note: TLS/SSL and client authentication must be enabled on X-Pack to use PKI.

Once the data provider is connected, X-Pack will then perform user authentication and grant role permissions based on the realms you have configured.

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

Create an External Data Source for Elasticsearch 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 Elasticsearch data.

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

CREATE DATABASE SCOPED CREDENTIAL elasticsearch_creds
WITH IDENTITY = 'elasticsearch_username', SECRET = 'elasticsearch_password';

Create an External Data Source for Elasticsearch

Execute a CREATE EXTERNAL DATA SOURCE SQL command to create an external data source for Elasticsearch 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 Elasticsearch. PUSHDOWN is set to ON by default, meaning the ODBC Driver can leverage server-side processing for complex queries.

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

Create External Tables for Elasticsearch

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

CREATE EXTERNAL TABLE Orders(
  OrderName [nvarchar](255) NULL,
  Freight [nvarchar](255) NULL,
  ...
) WITH ( 
  LOCATION='Orders',
  DATA_SOURCE=cdata_elasticsearch_source
);

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