如何安全地更新mongodb中的序列号 [英] how to update sequence number in mongodb safely
问题描述
在我的 mongodb 数据库中，有一个 'messages' 集合，它有一个字段 'order'，其值为整数
msg1.order=1, msg2.order=2, msg3.order=3, msg4.order=4, msg5.order=5, ...对于每条消息，表示消息子集合的有序序列.
同时，这些消息可以通过网页使用 jquery.sortable 重新排序.例如，如果我将位置 No.3 的 message 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 修饰符或其他方法可以进行此类更新，以便我可以一步或以安全的方式进行此类更新?
3 个示例文档:
<代码>{"author_id": "a","class": "原理",content_id":空，host_id":空，修改日期":1330935540，订单":1，发布日期":1330935540，分数":0，"text": "Hello World！","vote_down_count": 0,vote_up_count":0}{"author_id": "a","class": "原理",content_id":空，host_id":空，修改日期":1330935538，订单":2，发布日期":1330935538，分数":0，"text": "很高兴认识你.","vote_down_count": 0,vote_up_count":0}{"author_id": "a","class": "原理",content_id":空，host_id":空，修改日期":1330935548，订单":3，发布日期":1330935548，分数":0，"text": "太棒了！","vote_down_count": 0,vote_up_count":0}为了以原子方式执行此操作，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/原子+操作
如果它们是单个文档的一部分，以下内容将更改第二个和第三个子文档的顺序:
<前>> db.so.find().pretty();{"_id" : ObjectId("4f55e7ba362e2f2a734c92f8"),子":[{"author_id": "a","class": "原理",content_id":空，host_id":空，修改日期":1330935540，订单":1，发布日期":1330935540，分数":0，"text": "Hello World！",vote_down_count":0，vote_up_count":0},{"author_id": "a","class": "原理",content_id":空，host_id":空，修改日期":1330935538，订单":2，发布日期":1330935538，分数":0，"text": "很高兴认识你.",vote_down_count":0，vote_up_count":0},{"author_id": "a","class": "原理",content_id":空，host_id":空，修改日期":1330935548，订单":3，发布日期":1330935548，分数":0，"text": "太棒了！",vote_down_count":0，vote_up_count":0}]}查询:
<前>db.so.update({ _id: new ObjectId("4f55e7ba362e2f2a734c92f8")},{ $set : { 'subs.1.order' : 3, 'subs.2.order' : 2 } });结果:
<前>> db.so.find().pretty();{"_id" : ObjectId("4f55e7ba362e2f2a734c92f8"),子":[{"author_id": "a","class": "原理",content_id":空，host_id":空，修改日期":1330935540，订单":1，发布日期":1330935540，分数":0，"text": "Hello World！",vote_down_count":0，vote_up_count":0},{"author_id": "a","class": "原理",content_id":空，host_id":空，修改日期":1330935538，订单":3，发布日期":1330935538，分数":0，"text": "很高兴认识你.",vote_down_count":0，vote_up_count":0},{"author_id": "a","class": "原理",content_id":空，host_id":空，修改日期":1330935548，订单":2，发布日期":1330935548，分数":0，"text": "太棒了！",vote_down_count":0，vote_up_count":0}]}In my mongodb database, there is a 'messages' collection, it has a field 'order' which values integer
msg1.order=1, msg2.order=2, msg3.order=3, msg4.order=4, msg5.order=5, ...
for each message, represents an ordered sequence of a sub-collection of messages.
while, these messages can be re-sorted, via web page, using jquery.sortable. for example, If I move message on position No.3 to No.1, then I should change 'order' values to
msg1.order=2, msg2.order=3, msg3.order=1, msg4.order=4, msg5.order=5, ...
. are there any mongodb modifiers or other means of doing such update so that I can do such update in one step, or in a safe way?
3 sample documents:
{
"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
}
In order to do this atomically, all your three sample documents need to be part of the same document. MongoDB only does operations atomically on simple documents: http://www.mongodb.org/display/DOCS/Atomic+Operations
If they are part of a single document, the following would change the order of the 2nd and 3rd subdocument:
> 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
}
]
}
Query:
db.so.update(
{ _id: new ObjectId("4f55e7ba362e2f2a734c92f8")},
{ $set : { 'subs.1.order' : 3, 'subs.2.order' : 2 } }
);
Result:
> 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
}
]
}
这篇关于如何安全地更新mongodb中的序列号的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
