How to insert a huge amout of data to oracle database? - oracle

Question

First I query some data from user A and then I need to insert all this data to user B (user in oracle I mean) and I use Java to solve it. Below is my code:
while (ds.getResultSet().next()) {
ResultSet resultSet = ds.getResultSet();
ResultSetMetaData metaData = resultSet.getMetaData();
int count = metaData.getColumnCount();
StringBuilder sb = new StringBuilder();
sb.append("insert into ");
sb.append(tableName.toUpperCase());
sb.append("(");
for (int i = 1; i <= count; i++) {
sb.append(metaData.getColumnName(i));
if (i != count) sb.append(",");
else sb.append(")");
}
sb.append(" values(");
for (int i = 1; i <= count; i++) {
Object colValue = resultSet.getObject(i);
if (colValue == null) {
sb.append("null");
} else {
if (colValue instanceof Date) {
Date d = resultSet.getDate(i);
String dateStr = DateUtils.formatDate(d, "yyyy-MM-dd hh:mm:ss");
sb.append("to_date(");
sb.append("'");
sb.append(dateStr);
sb.append("','yyyy-MM-dd hh24:mi:ss')");
} else {
sb.append("'");
sb.append(resultSet.getObject(i));
sb.append("'");
}
}
if (i != count) sb.append(",");
else sb.append(")");
}
conn = datasource.getConnection();
System.out.println(sb.toString());
ps = conn.prepareStatement(sb.toString());
ps.execute();
}
So it works a bit, but when it inserts above 80 records oracle just collaspses, and it's warning me in the console:
Can you guys give some advice to me about this? Thanks for your time.

Answer 1

Do not use Java - just do it all in Oracle.
INSERT INTO b.table_name ( col1, col2, col3, col4 )
SELECT col1, col2, col3, col4
FROM a.table_name
WHERE some_column = some_value; -- Add filters if necessary
You avoid having to dynamically build the query by parsing the meta-data.
You avoid errors where you are not escaping single quotes.
Further to this, you avoid potential SQL Injection attacks where a user could enter something like the string value', (SELECT password_hash FROM users WHERE userid = 'Admin1' ) ) --

Answer 2

As you guys suggest, I changed my code like below:
Connection conn = DriverManager.getConnection(url, user, pwd);
PreparedStatement pspt = conn.prepareStatement("select * from SYS_DICT_TYPE");
ResultSet resultSet = pspt.executeQuery();
ResultSetMetaData metaData = resultSet.getMetaData();
int columnCount = metaData.getColumnCount();
StringBuilder sql = new StringBuilder();
sql.append("insert into TEST_SYS (");
for (int i = 1; i <= columnCount; i++) {
sql.append(metaData.getColumnName(i));
if (i != columnCount) sql.append(",");
}
sql.append(") values(");
for (int i = 1; i <= columnCount; i++) {
sql.append("?");
if (i != columnCount) sql.append(",");
}
sql.append(")");
String s = sql.toString();
PreparedStatement pspt2 = conn.prepareStatement(s);
while (resultSet.next()) {
for (int i = 1; i <= columnCount; i++) {
pspt2.setObject(i, resultSet.getObject(i));
}
pspt2.addBatch();
}
pspt2.executeBatch();
The wired thing is: At the first I build the statement end with a ';'
(the sql clause should like insert into tablename values(?,?);)
which cause ora-00933:SQL error.When I removed the ';' it worked perfectly well.Why could this happend?