Invalid state in SQL query for a function that was created with no errors.

Question

SQL> CREATE OR REPLACE FUNCTION overlap(in_start1 IN TIMESTAMP, in_end1 IN TIMESTAMP, in_start2 IN TIMESTAMP, in_end2 IN TIMESTAMP) RETURN NUMBER
2 IS
3
4 BEGIN
5 IF (in_start1 BETWEEN in_start2 AND in_end2 OR in_end1 BETWEEN in_start2 AND in_end2 OR in_start2 BETWEEN in_start1 AND in_end1) THEN
6 RETURN 0;
7 ELSE
8 RETURN 1;
9 END IF;
10 END;
11 /
Function created.
SQL> show errors;
No errors.
SQL>
SQL> SELECT * FROM tbl where overlaps(current_time,current_time+1,current_time-1,current_time+2) = 0;
SELECT * FROM tbl where overlaps(current_time,current_time+1,current_time-1,current_time+2) = 0
ERROR at line 1:
ORA-06575: Package or function OVERLAPS is in an invalid state
I do not understand why overlaps is returned as in invalid state in the query, when it was created with no errors earlier. Could anyone help me?

Answer 1

Marius
Looking at the logic you are trying to create it looks like you are looking for overlapping time periods.
Consider two date/time ranges:
Range 1 : T1 - T2
Range 2 : T3 - T4
Do they overlap?
1) No: T1 < T4 (TRUE)  T2 > T3 (FALSE)
T1 --- T2
           T3 --- T4
2) Yes: T1 < T4 (TRUE)  T2 > T3 (TRUE)
T1 ---------- T2
           T3 --- T4
3) Yes: T1 < T4 (TRUE)  T2 > T3 (TRUE)
T1 -------------------- T2
           T3 --- T4
4) Yes: T1 < T4 (TRUE)  T2 > T3 (TRUE)
               T1 ----- T2
           T3 --- T4
5) Yes: T1 < T4 (TRUE)  T2 > T3 (TRUE)
           T1 --- T2
       T3 ------------ T4
5) No: T1 < T4 (FALSE) T2 > T3 (TRUE)
                T1 --- T2
       T3 --- T4Answer: Yes they overlap if:
T1 < T4 AND T2 > T3
So you can code the logic in your SQL as simply:
SELECT *
FROM tbl
WHERE range1_start < range2_end
AND    range_1_end > range2_startIf you go around implementing PL/SQL functions for simple logic that can be achieved in SQL alone then you cause context switching between the SQL and PL/SQL engines which degrades performance. Wherever possible stick to just SQL and only use PL/SQL if absolutely necessary.