从 couchdb 检索数据（如何验证值是否在数据库中）

Question

how can I retrieve data from a couchdb database, not in a document of a database but in all the documents of the database. I already verified if a value was in a document but I want now to verify if a value is in a special database.

Answer 1

It's hard to be specific here, since you're not providing any example data. Do you mean if a particular value exists anywhere in any document, or if a specific field holds a specific value in any document?

If you mean the former, I'd advice you to come up with a better data model. So let's focus on the latter. Let's say your documents contain the field called special , and you want to know if any such documents has the value 99 in this field:

{
    ...
    "special": 99
}

Create a view keyed on the value:

function(doc) {
  if (doc && doc.special) {
    emit(doc.special, null);
  }
}

Now you can check if documents exist in this database for values of the special field:

# Look for the value 99
% acurl 'https://XYZ.cloudant.com/aaa/_design/test/_view/special?key=99'  
{"total_rows":3,"offset":2,"rows":[
   {"id":"a3c424e99f3cc9988a2553bb680ac7f8","key":99,"value":null}
]}

In my databse aaa there is one document, with the id a3c424e9... that has the value 99 in the special field. This is a so-called reverse index.