Support views and virtual schemas in pushdown responses

Detail name	Value
Changelog Number	5536
Type	Improvement
Status	Resolved
Fix Versions	EXASOL 6.0.7
Resolution Date	2018-01-09

Up to version 6.0.6, Exasol does not support views or virtual schema objects in pushdown responses from virtual schema adapters.

How To Reproduce

CREATE SCHEMA TEST;
CREATE TABLE T1(c1 int);

CREATE OR REPLACE JAVA ADAPTER SCRIPT JDBC_ADAPTER AS ...
CREATE VIRTUAL SCHEMA VS1 USING TEST.JDBC_ADAPTER WITH CONNECTION_STRING='jdbc:exa:localhost:1234' USERNAME='USER' PASSWORD='PWD' SCHEMA_NAME='TEST' IS_LOCAL='FALSE' SQL_DIALECT='EXASOL';

CREATE VIEW TEST.VIEW1 AS SELECT * FROM TEST.T1;
CREATE VIEW TEST.VIEW2 AS SELECT * FROM VS1.T1;
ALTER VIRTUAL SCHEMA VS1 REFRESH;

SELECT * FROM VS1.VIEW1; -- Query 1
SELECT * FROM VS1.VIEW2; -- Query 2

Query 1 leads to the error:

[04000] Adapter generated invalid pushdown query for virtual table VIEW1: The pushdown query returned by the Adapter contains a view (VIEW1). This is currently not supported. 

Fix
Version 6.0.7 now supports Query 1. To prevent unintentional recursions and therefore long query execution times, Exasol does not support Query 2 automatically. It still leads to an error:

[04000] Adapter generated invalid pushdown query for virtual table VIEW2: The pushdown query returned by the Adapter contains a virtual table (T1). This is currently not supported. (pushdown query: SELECT * FROM TEST.VIEW2)

However, it is possible to activate the support for Query 2 with a command line switch. Please contact Exasol support in case you need it.