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We are currently facing an issue with Window Functions in SAP Hana SPS12.
One of our error is when we are using STRING_AGG function.
Here is the code :
/*
CREATE TABLE TEST_STR_AGG (
GROUP_ID varchar(1)
, CLASS_ID varchar(5)
, MEMBER varchar(5)
);
*/
TRUNCATE TABLE TEST_STR_AGG;
INSERT INTO TEST_STR_AGG VALUES ('A', 'A_XX1', 'A0001');
INSERT INTO TEST_STR_AGG VALUES ('A', 'A_XX1', 'A0002');
INSERT INTO TEST_STR_AGG VALUES ('A', 'A_XX1', 'A0003');
INSERT INTO TEST_STR_AGG VALUES ('A', 'A_XX2', 'A0004');
INSERT INTO TEST_STR_AGG VALUES ('A', 'A_XX2', 'A0005');
INSERT INTO TEST_STR_AGG VALUES ('A', 'A_XX3', 'A0006');
INSERT INTO TEST_STR_AGG VALUES ('B', 'B_XX1', 'B0001');
INSERT INTO TEST_STR_AGG VALUES ('B', 'B_XX2', 'B0002');
INSERT INTO TEST_STR_AGG VALUES ('B', 'B_XX3', 'B0003');
INSERT INTO TEST_STR_AGG VALUES ('B', 'B_XX4', 'B0004');
INSERT INTO TEST_STR_AGG VALUES ('B', 'B_XX4', 'B0005');
INSERT INTO TEST_STR_AGG VALUES ('B', 'B_XX4', 'B0006');
SELECT GROUP_ID
, CLASS_ID
, STRING_AGG( MEMBER, ' ; ' **ORDER BY MEMBER ASC** ) as MEMBERS
FROM TEST_STR_AGG
GROUP BY GROUP_ID
, CLASS_ID ;
The STRING_AGG used to work perfectly with an ORDER BY clause before a patch install. Now, it is only working with a little volume of lines, as it works in the example I'm giving you. When we are working on more than 500k lines, some lines are disappearring from our result if we add the ORDER BY clause in the STRING_AGG. If we're not, it works.
We have the same issue on FIRST_VALUE and LAST_VALUE functions.
It seems to be a core optimization rule which is corrupting the results...
Does anybody know something about this, please ?
Many thanks

Yep, it's a known bug. Don't have the SAP note ready right now, but it's fixed in a current revision.
/--
Found the SAP note for this:
2365540 - Aggregation Function AVG() Returns ? / NULL Values When Used in Combination With STRING_AGG Including an ORDER BY Clause
Solution
Apply SAP HANA database Revision >= 112.07 (SPS11) or >= 122.02 (SPS12).
--/