Virtual Schemas: LISTAGG and GROUP_CONCAT Pushdown incomplete

Detail name	Value
Changelog Number	10802
Type	Bug
Status	Resolved
Affected Versions	Exasol 6.1.0, Exasol 6.2.0, Exasol 7.0.0
Fix Versions	Exasol 7.0.4, Exasol 6.2.13
Resolution Date	2020-11-26

Description

Queries on virtual schemas that contain the aggregate functions LISTAGG or GROUP_CONCAT face the following issues in pushdown:

• All LISTAGG and GROUP_CONCAT calls using an empty string as the delimiter are not pushed down:

• LISTAGG(a) (default delimiter is the empty string)
• LISTAGG(a, '')
• GROUP_CONCAT(a SEPARATOR '')

• If LISTAGG is pushed down, then its overflow behavior is missing from the pushdown.

Workaround

There is no workaround.

Fix

The empty string delimiter pushdown was fixed. The virtual schema API was extended to handle the overflow behavior of LISTAGG correctly. Thus, the fix requires a virtual schema adapter upgrade to use the LISTAGG pushdown functionality.

Changed behavior

LISTAGG and new FN_AGG_LISTAGG* capabilities were added to the virtual schema API. LISTAGG no longer uses the GROUP_CONCAT API.