How do I fill by chunks a clob inside a table while XML is generated?

Question

Hello everybody:
Needed to generate a single XML file from around 50 million rows, where the XML ouput matches not only row data but another default values for another elements and attributes (not from database but using strings and types with default values). Its generation will be a monthly task, so the process will repeat time by time. For generating that document, currently focus is based on using a batch process relying on Spring Batch, by using a single JDBC query where a join happens between a table and a materialized view (Both are datawarehouses, so it is not expected a change onto the data, and are single, non-partitioned tables). From my point of view, that approach uses: database resources, network resources, disk resources, and processing resources, including the price of making the join, sending to network, creating objects, validating, and making the file, finally wasting too much time generating that XML file. Promisse above that approach is to restart from the last execution point (savepoints) and to process by chunks of data (ResultSets). That processs currently is in development.
Seen Oracle has XML capabilites, another approach may be delegating the complete generation of that file to the database (Current version in use here is 10g release 2). My current approach is to generate a clob where I will put all the XML throughput and putting it inside a table (My first approach was to put directly into a disk file, unfortunately, isn't possible because internal policies). Considering limitations on memory, processing and disk space, needed to append a single row-as-xml to the clob as soon as it is rendered, and putting the clob inside the field as soon as possible, or putting the clob inside the field, and appending into it as the data is generated (preffered approach); also, considering its a very large operation, needed to make savepoints for each chunk of data processed (each 20,000 rows, as example). Some way I think it may be done is making a temporary clob, filling the clob while getting the rowid, using that rowid as savepoint (No other CRUD operations awaited for the table and the materialized view), and later appending the clob to the clob(s) in table (is there some way for append one clob to another one in table?). Explained all those points, how do I manage the process in order to achieve that goals, using a PL/SQL stored procedure while using built-in functions?.
Update: I did a small pseudocode where I describe my current approach:
Defining a cursor;
Creating a segment clob;
Creating a temporary clob;
Defining a chunk size;
Defining a temp rowid variable;
Defining a control number to be 0;
While cursor
     getting rowid and generating next row as xml into a temporary clob (XMLSerialize):
     increment the control number;
     if control number equals 1
write rowid variable to a control table;
     append the temporary clob to a segment clob;
     if control number is equals than the chunk size defined:
          append the segment clob to the clob inside a control table;
          restart the control number to be 0;
     else
          continue;
At this time, I'm with doubt about how to append the segment clob directly to the clob inside the control table (I find using that clob as PL/SQL variable would use too much memory and swap).
Any help shall be apreciated. Thanks in advance.

Answer 1

Well, of course it's looping. That's what the "while" statement does. What you need is more like this:
if (tableNumberJTextField.getText().equals("")){
  JOptionPane.showMessageDialog(null, "Table Number cannot be empty","Error", JOptionPane.ERROR_MESSAGE);
  tableNumberJTextField.requestFocusInWindow();
}and you want this code to be called every time tableNumberJTextField loses focus.