Re: Setting maximum size of a blob data type

From: Kim Berg Hansen <kibeha_at_gmail.com>
Date: Wed, 17 Sep 2014 18:33:57 +0200
Message-ID: <CA+S=qd2NU=werAV37STcnWfM7wVksfXCBuBDUSK8btpPNVCOXQ_at_mail.gmail.com>

DBMS_LOB.GETLENGTH counts as a userdefined function and won't work in a check constraint, true.
But deterministic builtin functions will, and that seems to work with both CLOBS and BLOBS.
A quick test (sql-developer script output):

> create table temp_text

(

   ID    NUMBER(3)     NOT NULL,
   TEXT_NAME         VARCHAR2(50),
   TEXT       CLOB constraint text_max_8192 check(length(text) < 8192)

)
table TEMP_TEXT created.
> declare

  l_text clob;
begin
  dbms_lob.createtemporary(l_text,false);   for i in 1..4 loop
    dbms_lob.append(l_text,lpad('X',1000,'X'));   end loop;
  insert into temp_text values (
    1, 'Clob length 4000', l_text
  );
  commit;
end;
anonymous block completed
> declare

  l_text clob;
begin
  dbms_lob.createtemporary(l_text,false);   for i in 1..8 loop
    dbms_lob.append(l_text,lpad('X',1000,'X'));   end loop;
  insert into temp_text values (
    1, 'Clob length 8000', l_text
  );
  commit;
end;
anonymous block completed
> declare

  l_text clob;
begin
  dbms_lob.createtemporary(l_text,false);   for i in 1..16 loop
    dbms_lob.append(l_text,lpad('X',1000,'X'));   end loop;
  insert into temp_text values (
    1, 'Clob length 16000', l_text
  );
  commit;
end;

Error starting at line : 41 in command - declare
  l_text clob;
begin
  dbms_lob.createtemporary(l_text,false);   for i in 1..16 loop
    dbms_lob.append(l_text,lpad('X',1000,'X'));   end loop;
  insert into temp_text values (
    1, 'Clob length 16000', l_text
  );
  commit;
end;
Error report -
ORA-02290: check constraint (HR.TEXT_MAX_8192) violated ORA-06512: at line 8
02290. 00000 - "check constraint (%s.%s) violated" *Cause: The values being inserted do not satisfy the named check

*Action: do not insert values that violate the constraint.
> select id, text_name, length(text) ln from temp_text

        ID TEXT_NAME                                                  LN
---------- -------------------------------------------------- ----------
         1 Clob length 4000                                         4000
         1 Clob length 8000                                         8000

> create table temp_photo

(

   ID    NUMBER(3)     NOT NULL,
   PHOTO_NAME         VARCHAR2(50),
   PHOTO       BLOB constraint photo_max_8192 check(length(photo) < 8192)

)
table TEMP_PHOTO created.
> declare

  l_photo blob;
begin
  dbms_lob.createtemporary(l_photo,false);   for i in 1..4 loop
    dbms_lob.append(l_photo,hextoraw(lpad('F0',2000,'F0')));   end loop;
  insert into temp_photo values (
    1, 'Blob length 4000', l_photo
  );
  commit;
end;
anonymous block completed
> declare

  l_photo blob;
begin
  dbms_lob.createtemporary(l_photo,false);   for i in 1..8 loop
    dbms_lob.append(l_photo,hextoraw(lpad('F0',2000,'F0')));   end loop;
  insert into temp_photo values (
    1, 'Blob length 8000', l_photo
  );
  commit;
end;
anonymous block completed
> declare

  l_photo blob;
begin
  dbms_lob.createtemporary(l_photo,false);   for i in 1..16 loop
    dbms_lob.append(l_photo,hextoraw(lpad('F0',2000,'F0')));   end loop;
  insert into temp_photo values (
    1, 'Blob length 16000', l_photo
  );
  commit;
end;

Error starting at line : 92 in command - declare
  l_photo blob;
begin
  dbms_lob.createtemporary(l_photo,false);   for i in 1..16 loop
    dbms_lob.append(l_photo,hextoraw(lpad('F0',2000,'F0')));   end loop;
  insert into temp_photo values (
    1, 'Blob length 16000', l_photo
  );
  commit;
end;
Error report -
ORA-02290: check constraint (HR.PHOTO_MAX_8192) violated ORA-06512: at line 8
02290. 00000 - "check constraint (%s.%s) violated" *Cause: The values being inserted do not satisfy the named check

*Action: do not insert values that violate the constraint.
> select id, photo_name, length(photo) ln from temp_photo

        ID PHOTO_NAME                                                 LN
---------- -------------------------------------------------- ----------
         1 Blob length 4000                                         4000
         1 Blob length 8000                                         8000

I am not certain from which version LENGTH started supporting LOBS, so you don't have to use DBMS_LOB.
The above was tested on 12.1.0.1.0, but I'm pretty certain it will work in 11 as well.

Regards

Kim Berg Hansen

http://dspsd.blogspot.com
kibeha_at_gmail.com
_at_kibeha

On Wed, Sep 17, 2014 at 5:10 PM, David Fitzjarrell <oratune_at_yahoo.com> wrote:

> That won't work as you cannot call dbms_lob.getlength in a CHECK
> constraint:
>
> SQL> create table temp_photo
> 2 (
> 3 ID NUMBER(3) NOT NULL,
> 4 PHOTO_NAME VARCHAR2(50),
> 5 PHOTO BLOB check(dbms_lob.getlength(photo) < 4097)
> 6 );
> PHOTO BLOB check(dbms_lob.getlength(photo) < 4097)
> *
> ERROR at line 5:
> ORA-00904: "DBMS_LOB"."GETLENGTH": invalid identifier
>
>
> SQL>
>
> It was a good thought.
>
> David Fitzjarrell
>
> Principal author, "Oracle Exadata Survival Guide"
>
>
> On Wednesday, September 17, 2014 8:12 AM, Kim Berg Hansen <
> kibeha_at_gmail.com> wrote:
>
>
> Set a CHECK constraint on the length?
>
>
>
> Regards
>
>
> Kim Berg Hansen
>
> http://dspsd.blogspot.com
> kibeha_at_gmail.com
> _at_kibeha
>
>
> On Wed, Sep 17, 2014 at 4:01 PM, Jeffrey Beckstrom <JBECKSTROM_at_gcrta.org>
> wrote:
>
> Is it possible to set a maximum size for a blob data type column?
>
> Jeffrey Beckstrom
> Lead Database Administrator
> Information Technology Department
> Greater Cleveland Regional Transit Authority
> 1240 W. 6th Street
> Cleveland, Ohio 44113
>
> .
>
>
>
>
>

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Received on Wed Sep 17 2014 - 18:33:57 CEST