Re: reducing JDBC String creation?



Daisy wrote:

With some help from this group, I improved my database throughput quite
a bit.  However, my code now creates a large number of Strings
(approximately 4 million in about 3 minutes) in PreparedStatements.  I
checked the source of String creation with OptimizeIt and Enerjy's
memory profiler.  The primary source of Strings are the
PreparedStatement.setInt() and PreparedStatement.setString() methods.

When I force a garbage collection, these are collected.  However, is
there a way to avoid so much String creation, particularly when writing
ints?  Is there a way to pass the existing int or String to the batch?


No, but there's no harm in the memory use. If the JVM needs memory, it will
run gc() and get those strings that are unneeded. You can't tell a driver to
use your own string etc, because you might alter it before/while the driver
was using it. It will always copy the data, especially if you're doing batches.
Joe Weinstein at BEA Systems



class DatabaseWriter{

int writeCount=0;

public DatabaseWriter(){

  PreparedStatement preparedStatement =
connection.prepareStatement("insert into       msgpersecond ( time ,
count ) values ( ? , ?  )");

  connection.setAutoCommit( false ); // turn off auto-Commit

}

public void process(Object input){

  preparedStatement.setLong( 1 , event.longVar );
  preparedStatement.setString( 2 , event.stringVar );
  preparedStatement.addBatch( );
  writeCount++:

  if (writeCount > 50) {
    updateCounts = preparedStatement.executeBatch( );
    connection.commit( );

preparedStatement.clearBatch( );
writeCount=0;
}

}
}

process() gets called a lot. 

Thanks


.

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