Segmentation Fault(core dump) - BLOB Locator use in Oracle D

[saumitra8361]

Hi,
I am trying to implement BLOB Locators concept in oracle db using pro*c/c++.
My DB table columns are of BLOB datatype and i want to insert/update data using BLOB Locators and that data is passed as parameter in the function.

As i have understood till this point the Locators concept, please comment if i am wrong:-

Declare the Locator variable - OCIBlobLocator *<locator_variable>;
Allocate the memory for Locator variable - EXEC SQL ALLOCATE :<locator_variable>;
Map the Locator variable with the DB Column - EXEC SQL SELECT <column_name> INTO :<locator_variable> FROM <table_name>;
Perform the operation(in this case UPDATE operation) - EXEC SQL UPDATE <table_name> SET <cloumn_name>=:<locator_variable>;
Free the memory of Locator variable - EXEC SQL FREE :<locator_variable>;

In my case i am having data passed as parameter in the function, so how to map the locator variable to particular column.

While updating the BLOB column i am getting the Segmentation Fault(core dump). So during UPDATE operation what <locator_variable> contains memory address or the data value.

I my opinion i am having address mapping problem, while updating the BLOB column.

Can you guys suggest any thing. Thanks for your help.

[Tim...]

Hi.

Not sure I can help with Pro*C. It's amny years since I've been down that road.

What I can see is you are doing a SELECT for the locator, but I think you should be doing a SELECT ... FOR UPDATE.

So looking at this from a PL/SQL perspective, to insert a new blob you will probably end up doing something like this.

Code: Select all

DECLARE
  l_bfile  BFILE;
  l_blob   BLOB;
BEGIN
  INSERT INTO tab1 (id, clob_data)
  VALUES (1, empty_blob())
  RETURN clob_data INTO l_blob;

  l_bfile := BFILENAME('IMAGES', 'MyImage.gif');
  DBMS_LOB.fileopen(l_bfile, Dbms_Lob.File_Readonly);
  DBMS_LOB.loadfromfile(l_blob, l_bfile, DBMS_LOB.getlength(l_bfile));
  DBMS_LOB.fileclose(l_bfile);

  COMMIT;
END;
/

To update an existing blob, you will probably do something like this.

Code: Select all

DECLARE
  l_bfile  BFILE;
  l_blob   BLOB;
BEGIN
  SELECT clob_data
  INTO   l_clob
  FROM   tab1
  WHERE  id = 1
  FOR UPDATE;

  l_bfile := BFILENAME('IMAGES', 'MyImage.gif');
  DBMS_LOB.fileopen(l_bfile, Dbms_Lob.File_Readonly);
  DBMS_LOB.loadfromfile(l_blob, l_bfile, DBMS_LOB.getlength(l_bfile));
  DBMS_LOB.fileclose(l_bfile);
END;
/

So you need to replicate that type of process in Pro*C.

Note sure this will help your specific problem, but might make you think a little differently.

You may get a better perspective by asking the question in the Pro*C forum on the OTN forums.

Sorry I can't be of more help.

Cheers

Tim...