CalciteRestAPIAdapter is publicly available on GitHub: https://github.com/oalekseev/CalciteRestAPIAdapter

It enables data retrieval from REST services using standard SQL syntax. It builds on the Apache Calcite(https://calcite.apache.org/) framework, which allows the creation of adapters for diverse data sources through JDBC. Proposal to contribute for community use is here (https://lists.apache.org/thread/jvbpz7rp7w76gqmshtz3y6bhcftk41c5)

Key Features:

• SQL access to arbitrary REST APIs via dynamic configuration

• Flexible adaptation to any REST service without code changes

• Uses Apache Freemarker for customizable REST request body generation

• Automatically converts any SQL filter conditions into Disjunctive Normal Form (DNF), enabling both simple and complex logical filtering

• Supports pagination: retrieves large result sets in sequential batches via configurable limit and offset parameters, preventing network overload and ensuring efficient data transfer

• Custom request fields and headers: allows injection of any additional fields (e.g., for authentication/authorization) or other custom parameters required by your API into REST request body, url, headers

A main challenge with REST services is their varied, often unpredictable request formats. To solve this, the adapter relies on Apache Freemarker templates: a new REST source is supported simply by providing an XML configuration describing its request structure – no rebuild and redeploy is needed.

Configurations (XML files) define:

• Service description

• Available tables

• Fields and types

• Mapping REST responses to SQL tables