Rolling back batch loads on the server
Batch loads always insert all of their data, even if one or more rows is rejected. Only the rows that caused errors in a batch are not loaded. When the database connection's AutoCommit property is true, batches automatically commit their transactions when they complete, so once the batch finishes loading, the data is committed.
In some cases, you may want all of the data in a batch to be successfully inserted—none of the data should be committed if an error occurs. The best way to accomplish this is to turn off the database connection's AutoCommit property to prevent batches from automatically committing themselves. Then, if a batch encounters an error, you can roll back the transaction after catching the BatchUpdateException
caused by the insertion error.
The following example demonstrates performing a rollback if any error occurs when loading a batch.
import java.sql.*;
import java.util.Arrays;
import java.util.Properties;
public class RollbackBatchOnError {
public static void main(String[] args) {
Properties myProp = new Properties();
myProp.put("user", "ExampleUser");
myProp.put("password", "password123");
Connection conn;
try {
conn = DriverManager.getConnection(
"jdbc:vertica://VerticaHost:5433/ExampleDB",
myProp);
// Disable auto-commit. This will allow you to roll back a
// a batch load if there is an error.
conn.setAutoCommit(false);
// establish connection and make a table for the data.
Statement stmt = conn.createStatement();
// Drop table and recreate.
stmt.execute("DROP TABLE IF EXISTS customers CASCADE");
stmt.execute("CREATE TABLE customers (CustID int, Last_Name"
+ " char(50), First_Name char(50),Email char(50), "
+ "Phone_Number char(12))");
// Some dummy data to insert. The one row won't insert because
// the phone number is too long for the phone column.
String[] firstNames = new String[] { "Anna", "Bill", "Cindy",
"Don", "Eric" };
String[] lastNames = new String[] { "Allen", "Brown", "Chu",
"Dodd", "Estavez" };
String[] emails = new String[] { "aang@example.com",
"b.brown@example.com", "cindy@example.com",
"d.d@example.com", "e.estavez@example.com" };
String[] phoneNumbers = new String[] { "123-456-789",
"555-444-3333", "555-867-53094535", "555-555-1212",
"781-555-0000" };
// Create the prepared statement
PreparedStatement pstmt = conn.prepareStatement(
"INSERT INTO customers (CustID, Last_Name, " +
"First_Name, Email, Phone_Number) "+
"VALUES(?,?,?,?,?)");
// Add rows to a batch in a loop. Each iteration adds a
// new row.
for (int i = 0; i < firstNames.length; i++) {
// Add each parameter to the row.
pstmt.setInt(1, i + 1);
pstmt.setString(2, lastNames[i]);
pstmt.setString(3, firstNames[i]);
pstmt.setString(4, emails[i]);
pstmt.setString(5, phoneNumbers[i]);
// Add row to the batch.
pstmt.addBatch();
}
// Integer array to hold the results of inserting
// the batch. Will contain an entry for each row,
// indicating success or failure.
int[] batchResults = null;
try {
// Batch is ready, execute it to insert the data
batchResults = pstmt.executeBatch();
// If we reach here, we inserted the batch without errors.
// Commit it.
System.out.println("Batch insert successful. Committing.");
conn.commit();
} catch (BatchUpdateException e) {
System.out.println("Error message: " + e.getMessage());
// Batch results isn't set due to exception, but you
// can get it from the exception object.
batchResults = e.getUpdateCounts();
// Roll back the batch transaction.
System.out.println("Rolling back batch insertion");
conn.rollback();
}
catch (SQLException e) {
// General SQL errors, such as connection issues, throw
// SQLExceptions. Your application should do something more
// than just print a stack trace,
e.printStackTrace();
}
System.out.println("Return value from inserting batch: "
+ Arrays.toString(batchResults));
System.out.println("Customers table contains:");
// Print the resulting table.
ResultSet rs = null;
rs = stmt.executeQuery("SELECT CustID, First_Name, "
+ "Last_Name FROM customers ORDER BY CustID");
while (rs.next()) {
System.out.println(rs.getInt(1) + " - "
+ rs.getString(2).trim() + " "
+ rs.getString(3).trim());
}
// Cleanup
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
Running the above example prints the following on the system console:
Error message: [Vertica][VJDBC](100172) One or more rows were rejected by the server.Rolling back batch insertion
Return value from inserting batch: [1, 1, -3, 1, 1]
Customers table contains:
The return values indicate whether each rows was successfully inserted. The value 1 means the row inserted without any issues, and a -3 indicates the row failed to insert.
The customers table is empty since the batch insert was rolled back due to the error caused by the third column.