来自 Java 代码的 Cassandra 更新表

Question

我正在尝试在Cassandra中为表实现各种分区。我的基本想法是给每一行分配一些磁盘编号，然后根据它们的磁盘编号将它们放在不同的视图中。对于循环分部，这是我正在做的：

System.out.println("nnRR PARTITIONINGnn");
    results = session.execute("select * from user;");
    int i=0, disk_no=0, total_disks=4;
    for(Row row: results)
    {
        String emailid = row.getString("email");
        disk_no = i++%total_disks;
        session.execute("update user set disk_no="+disk_no+" where email="+emailid+";");
        System.out.println("Disk "+disk_no+ ": "+ row.getString("firstname")+" "+row.getString("lastname")+" "+ row.getInt("age"));
    }
    session.execute("create materialized view RRDisk0 as select * from user where disk_no =0 and email is not null;");
    session.execute("create materialized view RRDisk1 as select * from user where disk_no =1 and email is not null;");
    session.execute("create materialized view RRDisk2 as select * from user where disk_no =2 and email is not null;");
    session.execute("create materialized view RRDisk3 as select * from user where disk_no =3 and email is not null;");

我面临的错误说：

Exception in thread "main" com.datastax.driver.core.exceptions.SyntaxError: line 1:44 no viable alternative at character '@'

请帮助我，我已经工作了两个小时，无法确定出了什么问题。

Answer 1

您忘记在更新查询中引用 emailid值。这应该是：

`session.execute("update user set disk_no="+disk_no+" where email='"+emailid+"';");`