Delete a nested object from a collection

Working with Data
1

The question I had is posted in stackoverflow. If somebody in this forum knows the answer kindly post solution.

2

Kindly re-post the question here so that we do not have to navigate into 2 different sites.

3

The collection I have is like:


	[{
		"day": 10,
		"orders": [{
			"id": 1,
			"items": {
				"uuid1": {
					"name": "item1",
					"status": false
				},
				"uuid2": {
					"name": "item2",
					"status": true
				},
				"uuid3": {
					"name": "item2",
					"status": false
				}
			}
		}]
	},
	{
		"day": 11,
		"orders": [{
			"id": 1,
			"items": {
				"uuid1": {
					"name": "item1",
					"status": false
				},
				"uuid2": {
					"name": "item2",
					"status": true
				},
				"uuid3": {
					"name": "item2",
					"status": false
				}
			}
		}]
	}]

I would like to delete items with status marked as true for day 10.
Tried the one below:

  db.<collection>.update (
    {day:  10},
    { $pull: { 
        orders: {items:  { status: 'true'} } }
    },
    {multi: true}
 );

The result is:

WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 0 })

and so it doesn’t delete.

How should we rewrite this update and pull query so that the items of day 10 marked with status as true are deleted?

1 Like
4

Few things first:

I am not sure of what is the expected results.

Do you want the document to become?

// Object uuid2 removed because status:true
{
		"day": 10,
		"orders": [{
			"id": 1,
			"items": {
				"uuid1": {
					"name": "item1",
					"status": false
				},
				"uuid3": {
					"name": "item2",
					"status": false
				}
			}
		}]
	}

// or object with id:1 removed from array orders because one uuid has status:true

{
		"day": 10,
		"orders": [ ]
	},

If uuid2 to be remove then $pull cannot be used because uuid2 is a field inside an object.

If not to late in you model life cycle, I would take a look at Building with Patterns: The Attribute Pattern | MongoDB Blog because the dynamic nature of uuid1, uuid2, … complicates your life.

5

Thanks Steevej.

The document should become like the first one you listed i.e. “uuid2” removed.
Its a legacy data and I found pull cannot be used but the other option is “$unset” and its very hard to frame a query that can match the value of the key and delete the key.