oracle PL/SQL stored procedure [closed] - oracle

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I have finished my first real PL/SQL stored proc, this stored proc works as expected. I am new to PL/SQL, could you please point anything wrong or bad coding ?
This code is assuming a naming convention, for example, 't_company' table will use 'companyId' as its primary key and its type is number.
Thank you very much.
create or replace
package body test_erp AS
procedure init_data is
begin
logMessage('procedure init_data');
SAVEPOINT do_insert;
insert into t_company(companyId, companyName) values(gen_key('t_company'), 'IBM');
COMMIT;
exception
WHEN OTHERS THEN
rollback to do_insert;
logMessage('roll back , due to '|| SQLERRM);
end init_data;
end test_erp;
It will call this function
create or replace
function gen_key(tblName varchar2)
return number is
l_key number := 1000;
l_tmpStr varchar(2000); -- not good, how to fix it ?
begin
l_tmpStr := substr(tblName, 3, length(tblName));
EXECUTE IMMEDIATE ' SELECT CASE WHEN MAX('||l_tmpStr||'Id) IS NULL THEN 1000 ELSE MAX('||l_tmpStr||'Id)+1 END FROM '|| tblName into l_key;
logmessage('gen primary key '|| tblName ||' '||l_key);
return l_key;
end;

Answer 1

Your key_gen procedure is rather problematic. Generating keys by doing a MAX(key)+1 is slow and will not work in a multiuser environment. Assuming you have two users, it is relatively easy for both users to see the same MAX(key) and try to insert rows with the same primary key.
Oracle provides sequences in order to efficiently generate primary keys in a multi-user environment. You would be much better served using sequences to generate your keys. Conventionally, you would create one sequence per table, i.e.
CREATE SEQUENCE company_seq;
Your INSERT statement would then be something like
insert into t_company(companyId, companyName) values(company_seq.nextval, 'IBM');
Or you could create a trigger on the table to automatically populate the primary key.
Additionally, while it is fine to catch exceptions in order to log them, you really want to re-raise that exception so that the caller is aware that the INSERT failed.

Answer 2

Using function in your case gen_key is very slow and it's incorrect database-written and also very inefficiently.
So my advice is to create SEQUENCE that is generally used for this.Then you should create TRIGGER for generating new PK for each INSERT or directly add it with NEXTVAL.
So, your SEQUENCE can looks like this:
CREATE SEQUENCE YOUR_COMP_SEQ
MINVALUE 1
MAXVALUE 999999
START WITH 1
INCREMENT BY 1
NOCACHE
;
Then i recommend to you use meant TRIGGER:
CREATE OR REPLACE TRIGGER AUTOSET_ID_COMP
BEFORE INSERT ON t_company
FOR EACH ROW
BEGIN
SELECT YOUR_COMP_SEQ.NEXTVAL INTO :NEW.companyId FROM DUAL;
END;
And finally just call query:
INSERT INTO t_company(companyName) VALUES('SomeValue');
If you don't want to create TRIGGER so you can do it directly like this:
INSERT INTO t_company(companyId, companyName)
VALUES(YOUR_COMP_SEQ.NEXTVAL, 'SomeValue');
Note: Of course, you can create for every TABLE its own SEQUENCE and then use TRIGGERS for each TABLE.
Note 2: Sequences are very good but there is some problem that for example you added to table 20 rows, so IDs are 1,2,3, ... etc. and for example you will delete 15. row and since this ID 15 you can't use, anymore.
Update:
Answer and Solution is updated after a little discussion with #Ben, thanks.