pullAll while removing embedded objects

Question

I have database with following document:

> db.bios.find({"name.first":"James"}).pretty()
{
        "_id" : 9,
        "name" : {
                "first" : "James",
                "last" : "Gosling"
        },
        "birth" : ISODate("1955-05-19T04:00:00Z"),
        "contribs" : [
                "Java",
                "C",
                "Scala",
                "UNIX"
        ],
        "awards" : [
                {
                        "award" : "The Economist Innovation Award",
                        "year" : 2002,
                        "by" : "The Economist"
                },
                {
                        "award" : "Officer of the Order of Canada",
                        "year" : 2007,
                        "by" : "Canada"
                },
                {
                        "award" : "nobel",
                        "by" : "Stockholm"
                },
                {
                        "award" : "nobel2",
                        "by" : "Stockholm"
                },
                {
                        "award" : "oscar",
                        "year" : 2015,
                        "by" : "Hollywood"
                }
        ]
}

I'm trying to write query to remove award objects issued by "Stockholm" or "Hollywood" from the awards array, but the below query does not work:

> db.bios.update({"name.first":"James"}, {$pullAll:{"awards.by":["Stockholm","Hollywood"]}})
WriteResult({
        "nMatched" : 0,
        "nUpserted" : 0,
        "nModified" : 0,
        "writeError" : {
                "code" : 16837,
                "errmsg" : "cannot use the part (awards of awards.by) to travers
e the element ({awards: [ { award: \"The Economist Innovation Award\", year: 200
2.0, by: \"The Economist\" }, { award: \"Officer of the Order of Canada\", year:
 2007.0, by: \"Canada\" }, { award: \"nobel\", by: \"Stockholm\" }, { award: \"n
obel2\", by: \"Stockholm\" }, { award: \"oscar\", year: 2015.0, by: \"Hollywood\
" } ]})"
        }
})
>

Similar query works for removing items from contribs array:

> db.bios.update({"name.first":"James"}, {$pullAll:{"contribs":["Java","Fortran"
]}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

so the problem here seems to be with the fact that I'm dealing with embedded object.

I'd appreciate your help.

Thanks!

Neil Lunn · Accepted Answer · 2015-01-23 04:09:56Z

10

The $pullAll operator is actually a "special case" shortcut which works on arrays with just values in them, such as your alternate case.

What you really want is $pull and it's argument is a "query" for the documents contained in the array. So your list then becomes an argument to $in:

db.bios.update(
   { "name.first": "James" },
   { 
      "$pull": { 
         "awards": { "by": { "$in": ["Stockholm", "Hollywood"] } } 
      } 
   }
)

So in your other example, a longer form of $pullAll would be:

db.bios.update(
   { "name.first": "James" },
   {
       "$pull": { "contribs": { "$in": ["Java","UNIX"] } }
   }
)

Same thing but just the "longhand" form.

answered Jan 23, 2015 at 4:09

Neil Lunn

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