英文:
How to Set Limit for options.FindOne() in go mongo-driver
问题
我看到Find()函数有一个SetLimit()方法，但是我没有看到为FindOne()设置限制的选项。由于我们在FindOne()中只搜索单个结果，所以我们甚至不需要限制它吗？它会自动处理限制吗？
我尝试使用options.FindOne()来设置限制，但是我没有找到方法来实现。
英文:
I see there is a way to SetLimit() for Find() func, But I don't see any options to set limit for FindOne() , Since we are searching single result out of FindOne() we don't even have to limit it ? Automatically it handles limit ?
Tried setting limit using 1options.FindOne()` , But I do not see a way to do that .
答案1
得分: 1
这是要翻译的内容：
这个行为没有在文档中记录，但是根据常识，Collection.FindOne() 的行为类似于 Limit=1。Collection.FindOne() 的返回值不能访问多个结果文档，这就是为什么 options.FindOne 甚至没有 SetLimit() 方法。
如果你查看源代码，可以看到：
// 为了确保只返回一个文档并且不保持游标打开，无条件地发送一个限制。
findOpts = append(findOpts, options.Find().SetLimit(-1))
注意到 FindOptions.Limit 的文档中写道：
// Limit 是返回的最大文档数。默认值为 0，表示返回匹配筛选条件的所有文档。负数的 Limit 指定结果文档应在一个批次中返回。默认值为 0。
Limit *int64
英文:
It's not documented, but it's common sense that Collection.FindOne() implies a behavior of that of Limit=1. The return value of Collection.FindOne() doesn't give access to multiple result documents, that's why options.FindOne doesn't even have a SetLimit() method.
If you check the source code, it's in there:
// Unconditionally send a limit to make sure only one document is returned and the cursor is not kept open
// by the server.
findOpts = append(findOpts, options.Find().SetLimit(-1))
Note that FindOptions.Limit documents that:
// Limit is the maximum number of documents to return. The default value is 0, which means that all documents matching the
// filter will be returned. A negative limit specifies that the resulting documents should be returned in a single
// batch. The default value is 0.
Limit *int64
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