public int executeModify(ModifyData data, Transaction tx)
{
Plan p = new TablePlan(data.tableName(), tx);
p = new SelectPlan(p, data.pred());
UpdateScan us = (UpdateScan)p.open();
int count = 0;
while (us.next())
{
Constant val = data.newValue().evaluate(us); //返回此处的表达式的常量值
us.setVal(data.targetField(), val); //设置要更改字段处的值
count++;
}
us.close();
return(count);
}
public int executeInsert(InsertData data, Transaction tx)
{
Plan p = new TablePlan(data.tableName(), tx);
UpdateScan us = (UpdateScan)p.open();
us.insert();
string fldname;
Constant val;
for (int i = 0; i < data.fields().Count; i++)
{
fldname = data.fields()[i];
val = data.vals()[i];
us.setVal(fldname, val);//一对一，对应的设置
}
us.close();
return(1);
}
//实现UpdateScan中所有接口
public void setVal(string fldname, Constant val)
{
UpdateScan us = (UpdateScan)s;
us.setVal(fldname, val);
}