MongoDB (Mongoose) 按数组查询

Question

Document Example:

{
    "_id" : ObjectId("5e41b8ecb6d9d829d07d3c5c"),
    "id" : "foo-bar-1",
    "__v" : 0,
    "books" : [ 
        {
            "_id" : ObjectId("5e41c81dbaa2b215082b52a1"),
            "chapters" : [ 
                {
                    "_id" : ObjectId("5e41c81dbaa2b215082b52a2"),
                    "title" : "Foo",
                    "pages" : 20
                },
                {
                    "_id" : ObjectId("5e41c81dbaa2b215082b52a3"),
                    "title" : "Bar",
                    "pages" : 34
                }
            ]
        }
    ],
    "last_updated" : ISODate("2020-02-10T15:10:50.027-05:00")
    }

Hi,

I would like to perform a MongoDB Query where I find the books with the exact same chapters. Ideally, I would like to perform something like this:

 const chapters = [{title: 'Foo', pages: 20},{title: 'Bar', pages: 34}];
 const book = await Model.findOne({'books.chapters': chapters});

However, from my testing this only works when the chapters array includes the _id fields. In the case I would like to use this I would not know what the subdocument schemas' id are. Is there a way to ignore them when comparing arrays and/or is there a better way to do this comparison.

Thank you for your time.

Answer 1

to match identical array fields the arrays must be identical in all ways...the fields, their order, and their values...title, pages, object id, etc

working with the current schema then you would need to filter out just the title (page count too?) via an aggregation pipeline query's stage and then use an intersect to establish the match...

depending on where you are in your development - if still early you could create a new array field of just chapterNames during the data input process...in addition to your existing array field Chapters...if that would suffice not sure if the page count is needed or not

still in this potential new field chapterTitles , as an array, to match the chapters must be in an identical order, identical spelling..

if you don't require that all chapters match - but are only looking for individual chapter name matches - then in the current schema you would set up a $unwind to separate apart the array into individual elements for matching purposes...this is also done in an aggregate pipeline stage...