如何通过单个请求仅从 CouchDB 获取某些文档的某些字段? [英] How to get from CouchDB only certain fields of certain documents with a single request?
问题描述
创建一个视图，该视图仅返回文档中值的子集，每个值的键和值都包含在 json 字符串中.就像如果一个给定的视图返回一个如下所示的文档，是否可以为一个请求获取一些字段信息?谢谢<代码>{总行数":10，偏移":3，行":[{"id":"doc1",关键":abc123"，价值": {"_id":"aaaa","_rev":"bbb","field1":"abc","field2":"bcd","field3":"cde","field4":"123","field5":"789","field6":"aa@email.com","field7":"ttt","field8":"iii",字段9":[{"field91":"tyui",字段 92":55555"}],"field10"::"0000","field11"::"55555",字段 12"::0030"…………}}我只想创建一个仅返回以下某些字段的视图:<代码>{"field1":"abc","field2":"bcd","field3":"cde","field4":"123","field5":"789","field6":"aa@email.com","field7":"ttt","field8":"iii",字段9":[{"field91":"tyui",字段 92":55555"}]}
create a view that return only a subset of values from a document, each with its key and value within a json string. like if one given view returns a document as this following, Is it possible to get some fields information for a one request? thank you
{
"total_rows":10,
"offset":3,
"rows":[{
"id":"doc1",
"key":"abc123",
"value": {
"_id":"aaaa",
"_rev":"bbb",
"field1":"abc",
"field2":"bcd",
"field3":"cde",
"field4":"123",
"field5":"789",
"field6":"aa@email.com",
"field7":"ttt",
"field8":"iii",
"field9":[{
"field91":"tyui",
"field92":"55555"
}],
"field10"::"0000",
"field11"::"55555",
"field12"::"0030".........
}
}
I just want to create a view that returns some fields only the following:
{
"field1":"abc",
"field2":"bcd",
"field3":"cde",
"field4":"123",
"field5":"789",
"field6":"aa@email.com",
"field7":"ttt",
"field8":"iii",
"field9":[{
"field91":"tyui",
"field92":"55555"
}]
}
推荐答案
一个映射函数，它发出一个只包含选定字段的新文档.例如，我们只映射 field1(字符串)和 field9(数组):
A map function that emits a new document with selected fields only. As an example, let's map field1 (a string) and field9 (an array) only:
function map(doc) {
emit(doc._id, {
field1: doc.field1,
field9: doc.field9
});
}
在上面的例子中，每个文档都会被触发，键是原始文档 ID，值是您需要的映射字段.如果您打算稍后添加 reduce 函数，这将非常有用.
In the above example, each document will be fired with a key being the original doc ID and the value being the mapped fields you require. This is useful if you are planning to add a reduce function later.
根据您的用例，您可能只想发出映射的对象:
Depending on your use case, you may just want to emit the mapped objects:
function map(doc) {
emit({
field1: doc.field1,
field9: doc.field9
});
}
请参阅 http://guide.couchdb.org/draft/views.html构建数据视图的文档很不错，你可以通过实验发现很多..
Please see http://guide.couchdb.org/draft/views.html The documentation on building data views is pretty good, you can discover a lot by experimenting..
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