我正在将数据库从Java DB复制到MySQL。所有表都在MySql中正确设置，我编写了一个复制数据库的方法。
方法中没有错误，它适用于大小有限的表格。但是对于大型桌来说它太慢了。复制7937记录花了大约5分29秒！由于一张表有230万条记录，我不得不等待超过26小时......
我在Netbeans中运行它，我的输出在这里:(批量大小= 2000）
run: ------ Copying table currency ------ 26 rows needs to be copied Executed batch for currency, inserted the last 26 elements ------ Finished copying table currency ------ ------ Copying table exchange ------ 31 rows needs to be copied Executed batch for exchange, inserted the last 31 elements ------ Finished copying table exchange ------ ------ Copying table markets ------ 82 rows needs to be copied Executed batch for markets, inserted the last 82 elements ------ Finished copying table markets ------ ------ Copying table trade ------ 2303371 rows needs to be copied Executed batch for trade, inserted 2000 elements Have copied a total of 2000/2303371 rows, 0% Executed batch for trade, inserted 2000 elements Have copied a total of 4000/2303371 rows, 0% Executed batch for trade, inserted 2000 elements Have copied a total of 6000/2303371 rows, 0% BUILD STOPPED (total time: 5 minutes 29 seconds)
所以当我看到这需要比预期更长的时间时，我停止了执行。
/**
*
* @param javadb Connection to the source database
* @param mysql Connection the target database
* @param orderedTables table names in the order they are to be copied (so no foreign key constraints error stuff happens)
*/
public static void copyFromJavaDBtoMySQL(Connection javadb, Connection mysql, String[] orderedTables, int batchSize){
Statement javadb_stmnt = null;
PreparedStatement mysql_stmnt = null;
try {
for (int i = 0; i < orderedTables.length; i++){
//Print out some information on which table isbeing copied and how many rows that table contains.
System.out.println("------ Copying table " + orderedTables[i] + " ------ ");
int numberRows = DataBase.executeCountQuery(orderedTables[i], null); //A helper method for getting rows in table
System.out.println(numberRows + " rows needs to be copied");
int totalNumberCopied = 0;
//Get resultset from source table
String selectQuery = "select * from " + orderedTables[i];
javadb_stmnt = javadb.createStatement();
ResultSet rs_select = javadb_stmnt.executeQuery(selectQuery);
//Creating insert query for target table. Query will be 'insert into <tablename> values (?, ?, ..., ?)'
int colCount = rs_select.getMetaData().getColumnCount();
String insert_query = "insert into " + orderedTables[i] + "( ";
String valuesSubstring = "values (";
for (int j = 0; j < colCount-1; j++){
insert_query += rs_select.getMetaData().getColumnName(j+1) + ", ";
valuesSubstring += "?, ";
}
insert_query += rs_select.getMetaData().getColumnName(colCount) + ") ";
insert_query += valuesSubstring + "?)";
//Use prepared statement with batches
mysql_stmnt = mysql.prepareStatement(insert_query);
int counter = 0;
//Iterate over resultset from source table
while (rs_select.next()){
//Add batch to insert statement from the current row in result set
for (int j = 1; j <= colCount; j++){
Object obj = rs_select.getObject(j);
mysql_stmnt.setObject(j, obj);
}
mysql_stmnt.addBatch();
//If I have added enough inserts, execute the batch insert
if (++counter == batchSize){
int[] arr = mysql_stmnt.executeBatch();
//Print out some progressinformation
totalNumberCopied += arr.length;
double progress = (1.0*totalNumberCopied) / (1.0*numberRows) * 100;
DecimalFormat df = new DecimalFormat("#");
System.out.print("Executed batch for "+orderedTables[i]+", inserted " + arr.length + " elements");
System.out.println("\t Have copied a total of " + totalNumberCopied + "/" + numberRows + " rows, " + df.format(progress) + "%");
//Reset counter for batch size
counter = 0;
}
}
//Insert the last elements
int[] arr = mysql_stmnt.executeBatch();
System.out.println("Executed batch for "+orderedTables[i]+", inserted the last " + arr.length + " elements");
System.out.println("------ Finished copying table " + orderedTables[i] + " ------ \n");
}
} catch (SQLException ex) {
Logger.getLogger(DataBaseCopier.class.getName()).log(Level.SEVERE, null, ex);
} finally {
try {
javadb.close();
mysql.close();
} catch (SQLException ex) {
Logger.getLogger(DataBaseCopier.class.getName()).log(Level.SEVERE, null, ex);
}
}
}