My CLOB insert with PreparedStatements WORKS but is SLOOOOWWW

Question

Hi All,
I am working on an application which copies over a MySQL database
to an Oracle database.
I got the code to work including connection pooling, threads and
PreparedStatements. For tables with CLOBs in them, I go through the
extra process of inserting the CLOBs according to Oracle norm, i.e.
getting locator and then writing to that:
http://www.oracle.com/technology/sample_code/tech/java/sqlj_jdbc/files/advanced/LOBSample/LOBSample.java.html (Good Example for BLOBs, CLOBs)
However, for tables with such CLOBs, I only get a Record per second insert
of about 1/sec!!! Tables without CLOBs (and thus, without the round-about-way)
of inserting CLOBs are approx. 10/sec!!
How can I improve the speed of my clob inserts / improve the code? At the moment, for
a table of 30,000 records (with CLOBs) it takes about 30,000 which is 8 hours!!!!
Here is my working code, which is run when my application notices that the table has
CLOBs. The record has already been inserted with all non-clob fields and the "EMPTY_BLOB()"
blank for the CLOB. The code then selects that row (the one just inserted), gets a handle on the
EMPTY_BLOB location and writes the my CLOB content (over 4000 characters) to that handles
and then closes the handle. At the very end, I do conn.commit().
Any tips for improving speed?
conn.setAutoCommit(false);
* This first section is Pseudo-Code. The actual code is pretty straight
* forward. (1) I create the preparedStatement, (2) I go record by record
* - for each record, I (a) loop through each column and run the corresponding
* setXXX to set the preparedStatement parameters, (b) run
* preparedStatement.executeUpdate(), and (c) if CLOB is present, run below
* actual code.
* During insertion of the record (executeUpdate), if I notice that
* a Clob needs to be inserted, I insert a "EMPTY_CLOB()" placeholder and set
* the flag "clobInTheHouse" to true. Once the record is inserted, if "clobInTheHouse"
* is actually "true," I go to the below code to insert the Blob into that
* newly created record's "EMPTY_CLOB()" placeholder
// clobSelect = "SELECT * FROM tableName WHERE "uniqueRecord" LIKE '1'
// I create the above for each record I insert and have this special uniqueRecord value to
// identify what record that is so I can get it below. clobInTheHouse is true when, where I
// insert the records, I find that there is a CLOB that needs to be inserted.
if(clobInTheHouse){
     ResultSet lobDetails = stmt.executeQuery(clobSelect);
     ResultSetMetaData rsmd = lobDetails.getMetaData();
     if(lobDetails.next()){
          for(int i = 1; i <= rsmd.getColumnCount(); i++){
             // if column name matches clob name, then go and do the rest
               if(clobs.contains(rsmd.getColumnName(i))){
                    Clob theClob = lobDetails.getClob(i);
                    Writer clobWriter = ((oracle.sql.CLOB)theClob).getCharacterOutputStream();
                    StringReader clobReader = new StringReader((String) clobHash.get(rsmd.getColumnName(i)));
                    char[] cbuffer = new char[30* 1024]; // Buffer to hold chunks of data to be written to Clob, the slob
                    int nread = 0;
                    try{
                         while((nread=clobReader.read(cbuffer)) != -1){
                              clobWriter.write(cbuffer,0,nread);
                    }catch(IOException ioe){
                       System.out.println("E: clobWriter exception - " + ioe.toString());
                    }finally{
                         try{
                              clobReader.close();
                              clobWriter.close();
                              //System.out.println("   Clob-slob entered for " + tableName);
                         }catch(IOException ioe2){
                              System.out.println("E: clobWriter close exception - " + ioe2.toString());
     try{
          stmt.close();
     }catch(SQLException sqle2){
conn.commit();

Answer 1

Can you use insert .. returning .. so you do not have to select the empty_clob back out.
[I have a similar problem but I do not know the primary key to select on, I am really looking for an atomic insert and fill clob mechanism, somone said you can create a clob fill it and use that in the insert, but I have not seen an example yet.]