如果mongodb中不存在该如何更新值

Question

db.books.find({ "status": "readED", $and: [ { "listingStatus": { $not: { $exists: true } } } ] }).forEach(function(book){

     db.getSiblingDB('reading').bookListing.find({"sellerSku": book.sellerSku, "sellerId":book.seller},{"sellerId": 1, "sellerSku": 1}).forEach(function(bookListing){

     printjson(bookListing);


});

});

when i run this, it gives

 {
    "_id" : ObjectId("582cb4ad5a5a380sadas038dd2f72"),
    "sellerId" : "e0a82c3d-079asdas0-49asda97-aasdascdf-0c320e3d7022",
    "sellerSku" : "te227"
}
{
    "_id" : ObjectId("582cb4ae5a5a380038dd2f73"),
    "sellerId" : "e0a82casdsa3d-07asdas90-4997-acdf-0c320e3d7022",
    "sellerSku" : "TE231"
}

so it means

there are books which is readed and listingstatus is not exist (normally listingstatus must be existed)

in reading db, there is booklisting colletion. Normally what i need to do is:

• if a book readed and listingstatus is not existed, need to update listingstatus if this books sellersku exists in booklisting collection.

instead of

  printjson(bookListing);

i need to update

book.update(listingstatu) in for each but is that possible in javascript?

What aboout this

db.getSiblingDB('book').books.update({ "seller": bookListing.sellerId, "sellerSku": bookListing.sellerSku },{ $set: {"listingStatus" : "LISTING_CREATED"}})

instead of

printjson(bookListing)

it wll again call book db.

but to test i made thi instead of

printjson

  db.getSiblingDB('book').books.find({ "seller": bookListing.sellerId, "sellerSku": bookListing.sellerSku },{ $set: {"listingStatus" : "LISTING_CREATED"}})

but it doesnot show anyhing

Answer 1

replace printjson(bookListing) by this:

        // set listingStatus 
        bookListing.listingStatus = "someRandomValue"; 
        // save the document. As a document already exist in the collection 
        // with this _id, it will update it. 
        db.books.save(listingStatus);

So your code becomes :

    db.books.find({ "status": "readED", $and: [ { "listingStatus": { $not: { $exists: true } } } ] }).forEach(function(book){

         db.getSiblingDB('reading').bookListing.find({"sellerSku": book.sellerSku, "sellerId":book.seller},{"sellerId": 1, "sellerSku": 1}).forEach(function(bookListing){

        // set listingStatus 
        bookListing.listingStatus = "someRandomValue"; 
        // save the document. As a document already exist in the collection 
        // with this _id, it will update it. 
        db.books.save(listingStatus);

    });
  });

This will update only matching documents