Question

在我的mongodb数据库中，有一个'messages'集合，它有一个字段'order'，它的值为整数

msg1.order=1, msg2.order=2, msg3.order=3, msg4.order=4, msg5.order=5, ...

每条消息的

表示消息子集的有序序列。

同时，可以使用jquery.sortable通过网页重新排序这些消息。例如，如果我将位置No.3上的消息移动到No.1，那么我应该将'order'值更改为

msg1.order=2, msg2.order=3, msg3.order=1, msg4.order=4, msg5.order=5, ...

。是否有任何mongodb修饰符或其他方法进行此类更新，以便我可以一步或安全地进行此类更新？

3份样本文件：

{
"author_id": "a",
"class": "principle",
"content_id": null,
"host_id": null,
"modified_date": 1330935540,
"order": 1,
"pub_date": 1330935540,
"score": 0,
"text": "Hello World！",
"vote_down_count": 0,
"vote_up_count": 0
}

{
  "author_id": "a",
  "class": "principle",
  "content_id": null,
  "host_id": null,
  "modified_date": 1330935538,
  "order": 2,
  "pub_date": 1330935538,
  "score": 0,
  "text": "Nice to meet you.",
  "vote_down_count": 0,
  "vote_up_count": 0
}
{
  "author_id": "a",
  "class": "principle",
  "content_id": null,
  "host_id": null,
  "modified_date": 1330935548,
  "order": 3,
  "pub_date": 1330935548,
  "score": 0,
  "text": "Great!",
  "vote_down_count": 0,
  "vote_up_count": 0
}

Answer 1

为了原子地执行此操作，您的所有三个示例文档都需要成为同一文档的一部分。 MongoDB只对简单文档进行原子操作：http://www.mongodb.org/display/DOCS/Atomic+Operations

如果它们是单个文档的一部分，则以下内容将更改第2和第3个子文档的顺序：

> db.so.find().pretty();
{
    "_id" : ObjectId("4f55e7ba362e2f2a734c92f8"),
    "subs" : [
        {
            "author_id" : "a",
            "class" : "principle",
            "content_id" : null,
            "host_id" : null,
            "modified_date" : 1330935540,
            "order" : 1,
            "pub_date" : 1330935540,
            "score" : 0,
            "text" : "Hello World！",
            "vote_down_count" : 0,
            "vote_up_count" : 0
        },
        {
            "author_id" : "a",
            "class" : "principle",
            "content_id" : null,
            "host_id" : null,
            "modified_date" : 1330935538,
            "order" : 2,
            "pub_date" : 1330935538,
            "score" : 0,
            "text" : "Nice to meet you.",
            "vote_down_count" : 0,
            "vote_up_count" : 0
        },
        {
            "author_id" : "a",
            "class" : "principle",
            "content_id" : null,
            "host_id" : null,
            "modified_date" : 1330935548,
            "order" : 3,
            "pub_date" : 1330935548,
            "score" : 0,
            "text" : "Great!",
            "vote_down_count" : 0,
            "vote_up_count" : 0
        }
    ]
}

查询：

db.so.update(
    { _id: new ObjectId("4f55e7ba362e2f2a734c92f8")},
    { $set : { 'subs.1.order' : 3, 'subs.2.order' : 2 } }
);

结果：

> db.so.find().pretty();
{
    "_id" : ObjectId("4f55e7ba362e2f2a734c92f8"),
    "subs" : [
        {
            "author_id" : "a",
            "class" : "principle",
            "content_id" : null,
            "host_id" : null,
            "modified_date" : 1330935540,
            "order" : 1,
            "pub_date" : 1330935540,
            "score" : 0,
            "text" : "Hello World！",
            "vote_down_count" : 0,
            "vote_up_count" : 0
        },
        {
            "author_id" : "a",
            "class" : "principle",
            "content_id" : null,
            "host_id" : null,
            "modified_date" : 1330935538,
            "order" : 3,
            "pub_date" : 1330935538,
            "score" : 0,
            "text" : "Nice to meet you.",
            "vote_down_count" : 0,
            "vote_up_count" : 0
        },
        {
            "author_id" : "a",
            "class" : "principle",
            "content_id" : null,
            "host_id" : null,
            "modified_date" : 1330935548,
            "order" : 2,
            "pub_date" : 1330935548,
            "score" : 0,
            "text" : "Great!",
            "vote_down_count" : 0,
            "vote_up_count" : 0
        }
    ]
}

如何安全地更新mongodb中的序列号

1 个答案: