如何在pymongo中删除嵌套文档

Question

I am working on a product development DB. Each product consists of several items and services. Each item has several properties, and I have an item collection. So I have many to many relationships.

I want to delete an item inside a product.

I have tried $pull , with update but I haven't got any luck. As I understand I need to find the document first and then delete the nested document with a $pull .

This is my flash route with the update:

main.route("/Producto/<string:prd_id>/<string:itm_id>/Borrar" , methods= ['GET','POST'])
@login_required
def borraprditm(prd_id,itm_id):
if request.method == 'POST':
    productos.update_one({'comp':usuario['comp_id'],"prd:id":prd_id},{ "$pull": {"items.itm_id":  {"itm_id": itm_id}}})
    flash('El Elemento ha sido eliminado', 'danger')
    return redirect(url_for('main.producto'))
return render_template('prditmdelete.html')

This is my Document:

_id  : 5cf572fc341026b937931734
comp : 13847
codigo : "prueba"
descripcion : "prueba 2"
um : "Prd"
cantidad : 0
precio : 0
prd_id : "0344131"
items :Array 

  0 : Object
  _id : 5cf18a08cf6ea6c98dd7861e
  comp : 13847
  codigo : "750-881"
  descripcion : "PFC 1Mb, CoDeSyS 2.3 - Mca WAGO"
  um : "Pza"
  precio : 1234
  itm_id : "0645566"

  1 : Object
  _id : 5cf18a13cf6ea6c98dd7861f
  comp : 13847
  codigo : "750-8202"
  descripcion : "PFC-200 Linux"
  um : "Pza"
  precio : 3453
  itm_id : "0915059"

  2 : Object
  _id : 5cf18a20cf6ea6c98dd78620
  comp : 13847
  codigo : "jack"
  descripcion : "tapa belden nodo"
  um : "Pza"
  precio : 20
  itm_id : "0918133"

Answer 1

You need to tell $pull which array to pull from, and then how to find the sub-document to pull:

{"$pull": {"items": {"itm_id": itm_id}}}

This means:

• for each document matching the query,
• pull from the "items" array
• any sub-documents that match the sub-query {"itm_id": itm_id}

See more details and examples on the MongoDB documentation