Conversion of a Base64EncodedXML CLOB to XMLTYPE

Question

I have an xml file which is base64 encoded and the base64 encoded file is stored as a clob. I want to do all the manipulation in PL/SQL and modify the clob column with one of xmltype
Heres the steps I've got so far:
i) convert the clob to a blob using dbms_lob.converttoclob
ii) Since this is now in binary format I'm asusming that I don't need to cast to raw
iii) decode the binary file using UTL_ENCODE.base64_decode
iv) add an additional column  temp_xml as type xml_type
v) update the temp_xml column with the values of the original column.
update <tablename>
               set temp_xml = xmltype(orig_clob_column) vi) At this stage I will see if I can read the xml in the new column and if all is successful, I will drop the orig_clob_column and rename temp_xml to orig_clob_column.
If I've missed anything or anyone's got some gotchas for me, it would be appreciated.
Message was edited by:
Keith Jamieson
Message was edited by:
Keith Jamieson

Answer 1

I am using Oracle 11g Windows and based on the example here:
http://www.peakretrieval.com/plsql/Chapter16/Convert.sql
create or replace PROCEDURE CONVERT_ME (
   v_blob_or_clob IN NUMBER,
   v_blob IN OUT BLOB,
   v_clob IN OUT CLOB,
   v_amount IN OUT NUMBER,
   v_blob_offset IN OUT NUMBER,
   v_clob_offset IN OUT NUMBER,
   v_lang_context IN OUT NUMBER,
   v_warning OUT NUMBER)
AS
BEGIN
   DBMS_LOB.OPEN(v_blob, DBMS_LOB.LOB_READWRITE);
   DBMS_LOB.OPEN(v_clob, DBMS_LOB.LOB_READWRITE);
   IF v_blob_or_clob = 0
   THEN
   DBMS_LOB.CONVERTTOBLOB(v_blob,
                          v_clob,
                          v_amount,
                          v_blob_offset,
                          v_clob_offset,
                          1,
                          v_lang_context,
                          v_warning);
   ELSE
   DBMS_LOB.CONVERTTOCLOB(v_clob,
                          v_blob,
                          v_amount,
                          v_clob_offset,
                          v_blob_offset,
                          1,
                          v_lang_context,
                          v_warning);
   END IF;
   DBMS_LOB.CLOSE(v_blob);
   DBMS_LOB.CLOSE(v_clob);
END;When I run this sample code
DECLARE
   v_clob_or_blob NUMBER;
   v_blob_locator BLOB;
   v_clob_locator CLOB;
   v_blob_offset NUMBER;
   v_clob_offset NUMBER;
   v_lang_context NUMBER := DBMS_LOB.DEFAULT_LANG_CTX;
   v_warning NUMBER;
   v_string_length NUMBER(10);
   v_source_locator BLOB;
   v_destination_locator BLOB;
   v_amount PLS_INTEGER;
   v_string CLOB;
BEGIN
   -- CONVERT CLOB TO BLOB
   SELECT description
   INTO v_clob_locator
   FROM book_samples
   WHERE book_sample_id = 1
   FOR UPDATE;
   SELECT misc
   INTO v_blob_locator
   FROM book_samples
   WHERE book_sample_id = 1
   FOR UPDATE;
   v_string_length := DBMS_LOB.GETLENGTH(v_blob_locator);
   v_amount := DBMS_LOB.GETLENGTH(v_clob_locator);
   DBMS_OUTPUT.PUT_LINE('The initial length of the BLOB is: '||v_string_length);
        v_clob_or_blob := 0; -- Convert clob to blob
        v_clob_offset := 1;
        v_blob_offset := 1;
        CONVERT_ME(v_clob_or_blob,
                v_blob_locator,
                v_clob_locator,
                v_amount,
                v_blob_offset,
                v_clob_offset,
                v_lang_context,
                v_warning);
   v_string_length := DBMS_LOB.GETLENGTH(v_blob_locator);
   DBMS_OUTPUT.PUT_LINE('The length of the BLOB post-conversion is: '||v_string_length);
   -- COPY BLOB FOR ONE ROW TO BLOB IN ANOTHER
   v_source_locator := v_blob_locator;
   SELECT misc
   INTO v_destination_locator
   FROM book_samples
   WHERE book_sample_id = 2
   FOR UPDATE;
   DBMS_LOB.COPY(v_destination_locator, v_source_locator, 32768, 1, 1);
   v_string_length := DBMS_LOB.GETLENGTH(v_destination_locator);
   DBMS_OUTPUT.PUT_LINE('The length of the BLOB post-copy is: '||v_string_length);
   -- COPY BLOB FOR RECORD 2 BACK TO A CLOB
   SELECT description
   INTO v_clob_locator
   FROM book_samples
   WHERE book_sample_id = 2
   FOR UPDATE;
   SELECT misc
   INTO v_blob_locator
   FROM book_samples
   WHERE book_sample_id = 2
   FOR UPDATE;
   v_string_length := DBMS_LOB.GETLENGTH(v_clob_locator);
   v_amount := DBMS_LOB.GETLENGTH(v_blob_locator);
   DBMS_OUTPUT.PUT_LINE('The initial length of the CLOB (record 2) is: '||v_string_length);
        v_clob_or_blob := 1; -- Convert blob to clob
        v_clob_offset := 1;
        v_blob_offset := 1;
        CONVERT_ME(v_clob_or_blob,
                v_blob_locator,
                v_clob_locator,
                v_amount,
                v_clob_offset,
                v_blob_offset,
                v_lang_context,
                v_warning);
   v_string_length := DBMS_LOB.GETLENGTH(v_clob_locator);
   SELECT description
   INTO v_string
   FROM book_samples
   WHERE book_sample_id = 2;
   DBMS_OUTPUT.PUT_LINE('The length of the CLOB post-conversion is: '||v_string_length);
   DBMS_OUTPUT.PUT_LINE('     ');
   DBMS_OUTPUT.PUT_LINE('The converted CLOB');
   DBMS_OUTPUT.PUT_LINE('==================');
   DBMS_OUTPUT.PUT_LINE(SUBSTR(v_string,1,150));
   DBMS_OUTPUT.PUT_LINE(SUBSTR(v_string,151,300));
EXCEPTION
   WHEN OTHERS
   THEN
      DBMS_OUTPUT.PUT_LINE('I''M BROKEN ... FIX ME!');
      DBMS_OUTPUT.PUT_LINE(SQLERRM);
END;I get the following error:
Length of blob before conversion
The conver_me procedure is broken ...
ORA-06502: PL/SQL: numeric or value error: invalid LOB locator specified: ORA-22275
Length of blob after conversion