[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.

[LKBrwn_DBA]

Originally Posted by 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
. . . E t c . . .
Can you guys suggest any thing. Thanks for your help.

Did you insert the row(s) using EMPTY_BLOB()?

[saumitra8361]

Originally Posted by LKBrwn_DBA

Did you insert the row(s) using EMPTY_BLOB()?

Hi LKBrwn_DBA,

Yes I tried to insert row using EMPTY_BLOB(), but that also didn't worked.

According to my knowledge EMPTY_BLOB() only initializes LOB Locator particular to that column.

[LKBrwn_DBA]

Originally Posted by saumitra8361

Yes I tried to insert row using EMPTY_BLOB(), but that also didn't worked.

According to my knowledge EMPTY_BLOB() only initializes LOB Locator particular to that column.

That is exactly how it works:

1) Insert EMPTY_BLOB()
2) Update the blob.

[saumitra8361]

Hi LKBrwn_DBA,

Now i get the solution . It involves following Steps:-

1) First Allocate Memory and Initialize LOB Locator

EXEC SQL ALLOCATE :<LOB_Locator>;

2) Then use INSERT/UPDATE to initialize LOB Column,
here we are using example of UPDATE query....

EXEC SQL UPDATE <Table_Name>
SET <LOB_Column> = EMPTY_BLOB(),(column = : <Value>,......)
(WHERE <condition_check>)
RETURNING <LOB_Column> INTO :<LOB_Locator> ;

Here, 'RETURNING' Clause will map LOB_Locator with LOB Column in the DB Table.

3) OPEN LOB Locator according to use.

EXEC SQL LOB OPEN :<LOB_Locator> READ WRITE;

4) Now WRITE data into LOB Locator.

EXEC SQL
LOB WRITE ONE :<amt> FROM :<Data_Buffer> INTO : <LOB_Locator>;

here, 'amt' is the no. of bytes need to be written.

5) CLOSE the LOB Locator after read/write Operation.

EXEC SQL LOB CLOSE :<LOB_Locator>;

6) FREE Allocated Memory of LOB Locator.

EXEC SQL FREE :<LOB_Locator>;