Oracle PL/SQL Bubble-Sorting - ORA-01403: no data found ORA-06512: at line 12 - oracle

Question

Here is the code:
declare
p_arr dbms_sql.Number_Table;
i pls_integer;
procedure do_sort(p_arr in out dbms_sql.Number_Table, p_asc in boolean default null, p_nulls_last in boolean default null) is
x pls_integer;
p_temp number;
begin
for i in 1..p_arr.COUNT-1
loop
for x in 2..p_arr.COUNT
loop
if p_arr(x) < p_arr(x-1)
then
p_temp := p_arr(x-1);
p_arr(x-1) := p_arr(x);
p_arr(x) := p_temp;
end if;
end loop;
end loop;
return;
end;
begin
p_arr(-1) := 0;
p_arr(0) := -2;
p_arr(1) := 10.1;
p_arr(2) := null;
p_arr(3) := 10.1;
p_arr(4) := -1;
do_sort(p_arr);
i := p_arr.first;
while i is not null loop
dbms_output.put_line('arr('||i||') = '||nvl(to_char(p_arr(i)), 'null')||';');
i := p_arr.next(i);
end loop;
end;
It gives me an error on line 12 - "No data found".
Respectively, the procedure "do_sort" on line 29 also fails.
Seems like the problem with nested loop, which I can't figure out for now.
When there is only "first-level" loop with some code in it, such as assigning new values to collection - it performs well.
Sorting block outside of procedure body also works.
Thanks in advance.

Answer 1

You're filling your number table with specific indexes:
p_arr(-1) := 0;
p_arr(0) := -2;
p_arr(1) := 10.1;
p_arr(2) := null;
p_arr(3) := 10.1;
p_arr(4) := -1;
But when you loop you are using index values from 1 to the count of elements, which is 6. There is no element with index 5 or 6, and when you try to refer to p_arr(5) there is no such element - hence the error. And you miss out those with indexes -1 and 0.
It works if you re-index your initial values:
p_arr(1) := 0;
p_arr(2) := -2;
p_arr(3) := 10.1;
p_arr(4) := null;
p_arr(5) := 10.1;
p_arr(6) := -1;
which then gets output:
arr(1) = -2;
arr(2) = 0;
arr(3) = 10.1;
arr(4) = null;
arr(5) = -1;
arr(6) = 10.1;
PL/SQL procedure successfully completed.
Notice what happens with your null value though... you cannot compare null with anything else, so p_arr(x) < p_arr(x-1) is undefined (but not true) when the null element is evaluated on both sides of that comparison. So, it doesn't move. You would need to decide where you want nulls to end up to determine how to modify the code to achieve that.
If you have a specific reason for starting your indexing at -1 instead of 1, you could still do that, and change the references inside your loop to be p_arr(x+2) etc., but it would be more confusing and error-prone. Or you coudl change your loop ranges to handle that instead:
for i in -1..p_arr.COUNT - 1 -- 2 less than previously, on each end of range
loop
for x in 0..p_arr.COUNT - 2 -- 2 less than previously, on each end of range
loop
... which gets the same result, using your original table population starting from index -1. Oracle Live SQL demo.
The indexes used inside the loops have to align with the indexes you use to populate the table, however you do it.