EXECUTE IMMEDIATE DROP FUNCTION causes Oracle SQL Developer to hang - sql

Question

I have the following script. But whenever I include the line EXECUTE IMMEDIATE 'DROP FUNCTION table_exists';, SQL Developer seems to hang. Any idea what could be causing it?
If I cancel the task, the script runs to completion but doesn't drop the function. However, I can simply run DROP FUNCTION table_exists; in my DB connection and it drops the table no problem. Is it some quirk of PL/SQL?
CREATE OR REPLACE FUNCTION table_exists(table_name VARCHAR2)
RETURN BOOLEAN
AS
table_count NUMBER := 0;
exists_sql VARCHAR2(255);
BEGIN
exists_sql := 'SELECT COUNT(1) FROM tab WHERE tname = :tab_name';
EXECUTE IMMEDIATE exists_sql INTO table_count USING table_name;
RETURN table_count > 0;
END;
/
DECLARE
TYPE tables_array IS VARRAY(2) OF VARCHAR2(25); -- change varray size if running on dev
tables tables_array;
BEGIN
tables := tables_array(
'FOO',
'BAR'
);
FOR table_element IN 1 .. tables.COUNT LOOP
DBMS_OUTPUT.PUT_LINE('Backing up data for ' || tables(table_element));
IF table_exists(tables(table_element) || '_ORIGINAL') THEN
DBMS_OUTPUT.PUT_LINE(tables(table_element) || '_ORIGINAL already exists');
ELSE
EXECUTE IMMEDIATE 'CREATE TABLE ' || tables(table_element) || '_ORIGINAL AS SELECT * FROM '|| tables(table_element);
END IF;
END LOOP;
EXECUTE IMMEDIATE 'DROP FUNCTION table_exists';
COMMIT;
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE ('Unexpected error: ' || sqlerrm);
ROLLBACK;
RAISE;
END;
/

Answer 1

Oracle won't drop a function which is being used in this very procedure.
Is there a workaround? Yes, at least one - submit a job which will do it in another session.
Sample tables (so that procedure won't fail because of that)
SQL> create table foo (id number);
Table created.
SQL> create table bar (id number);
Table created.
Create a function:
SQL> CREATE OR REPLACE FUNCTION table_exists(table_name VARCHAR2)
2 RETURN BOOLEAN
3 AS
4 table_count NUMBER := 0;
5 exists_sql VARCHAR2(255);
6 BEGIN
7 exists_sql := 'SELECT COUNT(1) FROM tab WHERE tname = :tab_name';
8 EXECUTE IMMEDIATE exists_sql INTO table_count USING table_name;
9
10 RETURN table_count > 0;
11 END;
12 /
Function created.
Is it here? Yes, it is:
SQL> desc table_Exists;
FUNCTION table_Exists RETURNS BOOLEAN
Argument Name Type In/Out Default?
------------------------------ ----------------------- ------ --------
TABLE_NAME VARCHAR2 IN
Run the main piece of code; note line #4 (declaration of a variable which will contain job number) and line #21 which submits a job.
SQL> DECLARE
2 TYPE tables_array IS VARRAY(2) OF VARCHAR2(25); -- change varray size if running on dev
3 tables tables_array;
4 i number; -- job number
5 BEGIN
6 tables := tables_array(
7 'FOO',
8 'BAR'
9 );
10
11 FOR table_element IN 1 .. tables.COUNT LOOP
12 DBMS_OUTPUT.PUT_LINE('Backing up data for ' || tables(table_element));
13 IF table_exists(tables(table_element) || '_ORIGINAL') THEN
14 DBMS_OUTPUT.PUT_LINE(tables(table_element) || '_ORIGINAL already exists');
15 ELSE
16 EXECUTE IMMEDIATE 'CREATE TABLE ' || tables(table_element) || '_ORIGINAL AS SELECT * FROM '|| tables(table_element);
17 END IF;
18 END LOOP;
19
20 -- EXECUTE IMMEDIATE 'DROP FUNCTION table_exists';
21 dbms_job.submit(i, 'begin execute immediate ''drop function table_exists''; end;');
22
23 COMMIT;
24
25 EXCEPTION
26 WHEN OTHERS THEN
27 DBMS_OUTPUT.PUT_LINE ('Unexpected error: ' || sqlerrm);
28 ROLLBACK;
29 RAISE;
30 END;
31 /
PL/SQL procedure successfully completed.
Is the function still here? Nope, it was dropped.
SQL> desc table_exists;
ERROR:
ORA-04043: object table_exists does not exist
SQL>