Virtual Schemas

SonarCloud results:

Overview

Exasol Virtual Schemas are an abstraction layer that makes external data sources accessible in our data analytics platform through regular SQL commands. The contents of the external data sources are mapped to virtual tables which look like and can be queried as any regular Exasol table.

Regardless of whether that source is a relational database like ours, or it's like the structure of GitHub repositories, the interface that users see is always the same.

This means an user familiar with SQL will immediately feel at home when accessing remote data through Virtual Schemas.

Version Requirements

From Virtual Schema 2.0.0 on you need Exasol 6.2 or later since it requires Java 9 to run. For Exasol 6.1 choose Virtual Schema 1.x or upgrade to 6.2.

Deprecation Warning

Please use the entry point

com.exasol.adapter.RequestDispatcher

in all your CREATE JAVA ADAPTER SCRIPT statements. The old entry point was removed with the Version 2.0.0 of Exasol's Virtual Schema.

Features

• Read access to data on remote data sources
• Data in those sources appears as tables inside Exasol and can be queried using regular SQL statements.
• Supports the following relational databases as sources: IBM DB2, Exasol, Generic JDBC-capable RDBMS, MySQL, Oracle, PostgreSQL, Amazon AWS Redshift, SAP HANA Microsoft SQLServer, Sybase, Teradata
• Supports Apache Impala (Hadoop-based analytical database) as a source
• Supports Apache Hive (Hadoop-based data warehouse) as source
• Supports access to file-based columnar storage (e.g. Apache Parquet files) via Amazon AWS Redshift Spectrum, Amazon AWS Athena, AWS Aurora and Google Big Query.
• Pushes down queries to the remote source (some sources)
• Supports sources with no / one / multiple catalogs or schemas
• Allows limiting metadata mapping to selected catalogs and / or schemas
• Allows redirecting log output to a remote machine
• Allows remote debugging with the Java Debugger

Customer Support

This is an open source project which is officially supported by Exasol. For any question, you can contact our support team.

Table of Contents

Information for Users

• User Guide
• Deployment Guide

Supported dialects:

1. Athena
2. Aurora
3. Big Query
4. DB2
5. Exasol
6. Hive
7. Impala
8. MySQL
9. Oracle
10. PostgreSQL
11. Redshift
12. SAP HANA
13. SQL Server
14. Sybase ASE
15. Teradata
16. Generic

Information for Developers

• Virtual Schema API Documentation
• Developing and Testing an SQL Dialect
• Step-by-step guide to writing your own SQL dialect
• Remote Logging
• Remote Debugging
• Troubleshooting
• Versioning

Dependencies

Run Time Dependencies

Running the Virtual Schema requires a Java Runtime version 9 or later.

Dependency	Purpose	License
JSON-P	JSON Processing	CDDL-1.0
Exasol Script API	Accessing Exasol features	MIT License
JDBC driver(s), depending on data source	Connecting to the data source	Check driver documentation

Build Time Dependencies

Dependency	Purpose	License
Apache Derby	Pure-Java embedded database	Apache License 2.0
Apache HTTP Components	HTTP communication	Apache License 2.0
Apache Maven	Build tool	Apache License 2.0
Equals Verifier	Testing equals(...) and hashCode() contracts	Apache License 2.0
Exasol Virtual Schema Common	Common module of Exasol Virtual Schemas adapters	MIT License
Exec Maven Plugin	Helps execute system and Java programs.	Apache License 2.0
Java Hamcrest	Checking for conditions in code via matchers	BSD License
JSONassert	Compare JSON documents for semantic equality	Apache License 2.0
JUnit	Unit testing framework	Eclipse Public License 1.0
J5SE	JUnit5 extensions to test Java System.x functions	Eclipse Public License 2.0
Mockito	Mocking framework	MIT License
SnakeYaml	YAML parsing	Apache License 2.0