向大数据数据库中插入值时，还要判断插入是否重复，然后插入。如何提高效率

在表中创建一个timestamp列，使用key+timestamp，每次更新都更新timestamp，在更新前先来判断读时与更新时的timestamp是否一致。例子： 

    Connection conn = null;
       
    try {
        PreparedStatement stmt;
        long ts; //timestamp
       
        conn = ds.getConnection( );
        stmt = conn.prepareStatement("UPDATE Customer " +
                                     "SET firstName = ?, lastName = ?, phone = ?, " +
                                     "birthDay = ?, lastUpdateTS = ? " +
                                     "WHERE id = ? AND lastUpdateTS = ?");//注意条件
        stmt.setString(1, firstName);
        stmt.setString(2, lastName);
        stmt.setString(3, phone);
        stmt.setDate(4, birthDate);
        stmt.setLong(5, ts = System.currentTimeMillis( ));
        stmt.setInt(6, id);
        stmt.setLong(7, lastUpdateTS);
        stmt.executeUpdate( );
        lastUpdateTS = ts;
    }
    catch( SQLException e ) {
        e.printStackTrace( );
    }
    finally {
        if( conn != null ) {
            try { conn.close( ); }
            catch( SQLException e ) { }
        }
    }