I played with this a bit.
First, I created some test data with one column corrupted with a single random character
of 0-31 replacing a random char in that column 20% of the rows of the table.
Peter's function correctly found all of the rows in 7.5 seconds.
Stephane's function ran in 3.5 seconds, but didn't find any of
the rows. I didn't attempt to correct the code.
Then I tried a function based on owa_pattern.regex. My initial attempts
didn't return the correct rows, as the regex pattern needed some tuning.
I didn't attempt to fix it, as it was woefully slow, about 30 seconds.
Regex in the WHERE clause in 10g will be nice.
Jared
| "Stephane Faroult" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED] 10/10/2003 07:09 AM
|
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> cc: Subject: RE: RE: RE: Find an unprintable character inside a column.... |
>Some people have requested this code, so I thought
>you might as well all
>have the chance to pick it to bits... Its a
>function called BAD_ASCII, and
>it hunts out for any ascii characters with an ascii
>value of less than 32 in
>a specified field. (Acknowledgments to my colleague
>Keith Holmes for help
>with this code.)
>
>Use it as follows:
>
>Where a field called DATA in a table TABLE_1 may
>contain an ascci character
>with a value less than 32 (ie a non-printing
>character), the following SQL
>will find the row in question:
>
>select rowid,DATA,dump(DATA) from TABLE_1
>where BAD_ASCII(DATA) > 0;
>
>You could use the PK of the table instead of rowid,
>of course. You will also
>note that I select the DATA field in both normal
>and ascii 'dump' mode, the
>better to locate where the corruption is located.
>
>peter
>edinburgh
>...................................
>
>Source as follows:
>
>
>Function BAD_ASCII
> (V_Text in char)
> return number
>is
> V_Int number;
> V_Count number;
>begin
>--
>V_Int := 0;
>V_Count := 1;
>while V_Count<=length(rtrim(V_Text)) and V_Int=0
> loop
> if ascii(substr(V_Text, V_Count, 1))<32 then
> V_Int := V_Count;
> end if;
> V_Count := V_Count + 1;
>end loop;
>return V_Int;
>--
>exception
> when others then
> return -1;
>end BAD_ASCII;
>/
>
Peter,
I think that you can make this code 25% faster when the data is clean (which hopefully is the general case) by using 'replace', more efficient than a PL/SQL loop, to check whether you have some rubbish (sort of). It will not tell you where the bad character is, however - which means that then you can loop to look for it.
Here is what I would suggest :
create or replace Function BAD_ASCII (V_Text in char)
return number
is
V_Int number;
V_Count number;
begin
if (replace(V_text, chr(0)||chr(1)||chr(2)||chr(3)||
chr(4)||chr(5)||chr(6)||chr(7)||
chr(8)||chr(9)||chr(10)||chr(11)||
chr(12)||chr(13)||chr(14)||chr(15)||
chr(16)||chr(17)||chr(18)||chr(19)||
chr(20)||chr(21)||chr(22)||chr(23)||
chr(24)||chr(25)||chr(26)||chr(27)||
chr(28)||chr(29)||chr(30)||chr(31),
'--------------------------------')
= V_text)
then
return 0;
else
V_Int := 0;
V_Count := 1;
while V_Count<=length(rtrim(V_Text)) and V_Int=0
loop
if ascii(substr(V_Text, V_Count, 1))<32 then
V_Int := V_Count;
end if;
V_Count := V_Count + 1;
end loop;
return V_Int;
end if;
--
exception
when others then
return -1;
end BAD_ASCII;
/
Regards,
Stephane Faroult
Oriole
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