你如何正确地添加/操纵实体组中的数千名儿童？ [英] How do you properly add/manipulate thousands of children in an entity group?

问题描述

这进一步到我的处理大量对象的上一个问题在BigTables / JDO中。

假设 TransactionAccount 最终可能在其< c $ c> transactions list，这与Goodle应用程序引擎是如何工作的？

如何在没有整个列表被加载到内存中？ （假设10000个对象不应该加载到内存中？）

我不想问你如何做我的功课，我只是有不知道从哪里开始解决这个问题，应用程序引擎文档和谷歌搜索没有帮助：（

  / / example only，not not to compile 
 @PersistenceCapable 
 public class TransactionAccount {
 @PrimaryKey 
 @Persistent（valueStrategy = IdGeneratorStrategy.IDENTITY）
 public key key; 
私人长余额; 
私人长期transactionCount; 
 @Element（依赖=true）
私人列表< Transaction> transactions = new ArrayList< Transaction>（）; 
 ... 
 public long getBalance（）{return balance;} 
} 
 
 @PersistenceCapable 
 private class Transaction {
 @PrimaryKey 
 @Persistent（valueStrategy = IdGeneratorStrategy.IDENTITY）
公钥键; 
 public日期日期; 
公开长期金额; 
} 
  

提出这个问题但未解决在以下谷歌群组发布。

@NotPersistent ，以便它根本不存储在数据存储中。>解决方案

您可以通过祖先查询获取给定TransactionAccount的交易实体>（详见此主题）。因此，您应该能够为给定账户存储任意数量的交易，因为它们并非全部存储在账户实体中。

一个不那么激烈的措施是使用此注释标记未标记的交易属性：

  @Extension（vendorName =datanucleus，key =gae.unindexed ，value =true）
  

账户的交易仍然存储在列表中，但他们wouldn不会被索引，这会使它更加可行。但是，如果您使用 @NotPersistent ，那么您将达到1MB实体大小的10-100k次交易限制。

This further to my previous question on handling large numbers of objects in BigTables/JDO.

Assuming a TransactionAccount could end up with as many as 10,000 objects in its transactions list, how does this work with Goodle app engine?

How do you add objects to such a large list without the whole list being loaded into memory? (The assumption is that 10,000 objects shouldn't be loaded into memory?)

I am not trying to ask you how to do my homework, I just have no idea where to start to solve this, the app engine documentation and google searching is not helping :(

// example only, not meant to compile
@PersistenceCapable
public class TransactionAccount {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    public Key key;
    private long balance;
    private long transactionCount;
    @Element(dependent = "true")
    private List<Transaction> transactions = new ArrayList<Transaction>();
    ....
    public long getBalance() { return balance; }
}

@PersistenceCapable
private class Transaction {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    public Key key;
    public Date date;
    public long amount;
}

This question is raised but not resolved in the following google groups post.

解决方案

try marking the transactions property @NotPersistent, so that it's not stored in the datastore at all. you can get the Transaction entities for a given TransactionAccount with an ancestor query (more in this thread). with that, you should be able to store arbitrarily many transactions for a given account, since they're not all stored in the account entity.

a less drastic measure would be to mark the transactions property unindexed with this annotation:

@Extension(vendorName = "datanucleus", key = "gae.unindexed", value="true") 

the account's transactions would still be stored in the list, but they wouldn't be indexed, which would make it a bit more feasible. still, you'd hit the 1MB entity size limit around 10-100k transactions, which wouldn't be a problem if you use @NotPersistent.

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