Recursive CTE throws temp tablespace is empty error

Question

I need to aggregate the contents of multiple rows into a row as a delimited text. Here's the simplified table with sample data which represents what i want to do.

CREATE TABLE SPD_OWNER.EMP (
    EMPID NUMBER,
    NAME VARCHAR2(20),
    MGRID NUMBER,
    DEPT VARCHAR2(5)
);

INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(1, 'GPM', NULL, 'IT');
INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(2, 'SPM', 1, 'IT');
INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(3, 'PM', 2, 'IT');
INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(4, 'Dev1', 3, 'IT');
INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(5, 'Dev2', 4, 'IT');

-- query which has issue
WITH tmp (rnum,dept,id) AS 
    (SELECT rownum rnum, dept, to_char(empid) AS id FROM (SELECT dept, empid FROM emp WHERE dept='IT' ORDER BY empid)),
cte (rnum,dept,id) AS
    (SELECT rnum, dept, id FROM tmp WHERE rnum=1
        UNION ALL
    SELECT cte.rnum+1, tmp.dept, cte.id||'/'||tmp.id FROM cte JOIN tmp on tmp.rnum=cte.rnum+1)
SELECT * FROM cte cte1 
WHERE rnum=(SELECT max(rnum) FROM cte cte2 WHERE cte1.dept=cte2.dept);

Am expecting below output.

5 IT 1/2/3/4/5

But running above query gives me an error SQL Error [25153] [99999]: ORA-25153: Temporary Tablespace is Empty

Isn't the condition tmp.rnum=cte.rnum+1 sufficient to break the recursive loop? Here's what am imagining to be happening.

1. 1st select (above union all) will select rnum=1
2. 1st recursive iteration will select tmp.rnum=cte.rnum+1, i.e. tmp.rnum=2
3. 2nd recursive iteration will select tmp.rnum=3
4. and so on till this condition is invalid, i.e. when cte.rnum=5 (because then tmp.rum=5+1 will not have matching record)

Am assuming that am getting the error since it's going into infinite loop. What am i missing?

Side Note: Am using Oracle DB, so i can easily do this using LISTAGG. But i also want to run this query in H2 DB. So i want to have a solution that uses standard sql. Am open to other ways to achieve the same result.

Answer 1

That error does not mean the temp tablespace got full, it means it is empty. Empty as no tempfile in it.

CREATE TABLE EMP (
    EMPID NUMBER,
    NAME VARCHAR2(20),
    MGRID NUMBER,
    DEPT VARCHAR2(5)
);

INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(1, 'GPM', NULL, 'IT');
INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(2, 'SPM', 1, 'IT');
INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(3, 'PM', 2, 'IT');
INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(4, 'Dev1', 3, 'IT');
INSERT INTO EMP (EMPID, NAME, MGRID, DEPT) VALUES(5, 'Dev2', 4, 'IT');

Query:

SQL> WITH tmp (rnum,dept,id) AS
    (SELECT rownum rnum, dept, to_char(empid) AS id FROM (SELECT dept, empid FROM emp WHERE dept='IT' ORDER BY empid)),
cte (rnum,dept,id) AS
    (SELECT rnum, dept, id FROM tmp WHERE rnum=1
        UNION ALL
    SELECT cte.rnum+1, tmp.dept, cte.id||'/'||tmp.id FROM cte JOIN tmp on tmp.rnum=cte.rnum+1)
SELECT * FROM cte cte1
  8  WHERE rnum=(SELECT max(rnum) FROM cte cte2 WHERE cte1.dept=cte2.dept);

      RNUM DEPT  ID
---------- ----- --------------------
         5 IT    1/2/3/4/5

Now if I drop the tempfile:

SQL> select file_id from dba_temp_files;

   FILE_ID
----------
         1

SQL> alter database tempfile 1 drop;

Database altered.

SQL> select file_id from dba_temp_files;

no rows selected

SQL> WITH tmp (rnum,dept,id) AS
    (SELECT rownum rnum, dept, to_char(empid) AS id FROM (SELECT dept, empid FROM emp WHERE dept='IT' ORDER BY empid)),
cte (rnum,dept,id) AS
    (SELECT rnum, dept, id FROM tmp WHERE rnum=1
        UNION ALL
    SELECT cte.rnum+1, tmp.dept, cte.id||'/'||tmp.id FROM cte JOIN tmp on tmp.rnum=cte.rnum+1)
SELECT * FROM cte cte1
  8  WHERE rnum=(SELECT max(rnum) FROM cte cte2 WHERE cte1.dept=cte2.dept);
WITH tmp (rnum,dept,id) AS
*
ERROR at line 1:
ORA-25153: Temporary Tablespace is Empty

Check DBA_TEMP_FILES and fix your temporary tablespace.