Updating large amounts of data typically is done by preparing an Insert statement and executing that statement multiple times, resulting in numerous network roundtrips. To reduce the number of JDBC calls and improve performance, you can send multiple queries to the database at a time using the addBatch method of the PreparedStatement object. For example, let us compare the following examples, Case 1 and Case 2.
Case 1: Executing Prepared Statement Multiple Times
PreparedStatement ps = conn.prepareStatement(
"INSERT INTO employees VALUES (?, ?, ?)");
for (n = 0; n < 100; n++) {
ps.setString(name[n]);
ps.setLong(id[n]);
ps.setInt(salary[n]);
ps.executeUpdate();
}
Case 2: Using a Batch
PreparedStatement ps = conn.prepareStatement(
"INSERT INTO employees VALUES (?, ?, ?)");
for (n = 0; n < 100; n++) {
ps.setString(name[n]);
ps.setLong(id[n]);
ps.setInt(salary[n]);
ps.addBatch();
}
ps.executeBatch();
In Case 1, a prepared statement is used to execute an Insert statement multiple times. In this case, 101 network roundtrips are required to perform 100 Insert operations: one roundtrip to prepare the statement and 100 additional roundtrips to execute its iterations. When the addBatch method is used to consolidate 100 Insert operations, as demonstrated in Case 2, only two network roundtrips are required—one to prepare the statement and another to execute the batch. Although more database CPU cycles are involved by using batches, performance is gained through the reduction of network roundtrips. Remember that the biggest gain in performance is realized by reducing network communication between the JDBC driver and the database server.
