Wrong result for emitting UDF with GROUP BY columns sharing an expression

Detail name	Value
Changelog Number	8254
Type	Bug
Status	Resolved
Affected Versions	Exasol 6.1.0, Exasol 6.2.0
Fix Versions	Exasol 6.2.0, Exasol 7.0.0, Exasol 6.1.5
Resolution Date	2019-07-18

Bug

A SELECT query sometimes returns a wrong result if it matches all of the following conditions:

• The FROM clause contains a subquery selecting values from an emitting UDF.
• There is no WHERE clause.
• The GROUP BY clause refers to two or more columns sharing a common expression.

Example

Here the common expression is MOD(VAL, 10).

SELECT DIV(MOD(VAL, 10), 4), DIV(MOD(VAL, 10), 5), MAX(VAL) FROM
(
    SELECT EMITTING_UDF(COL)
    FROM TAB
)
GROUP BY 1, 2;

Workarounds

• Either add a WHERE clause which is more complex than WHERE TRUE but does not change the result, e.g. WHERE VAL IS NULL OR VAL IS NOT NULL,
• or use the database parameter -noshortcuts=1 (not recommended because it might affect other queries).