MongoDB pull based on partial array?

Question

I can do a $pull for a simple document:

> db.users.find();
{ "_id" : 4, "sessions" : [ { "sid" : "foo1" }, { "sid" : "bar" } ] }

> db.users.update({}, {"$pull": {sessions: {"sid" : "bar"}}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

But if I have more information on the session:

> db.users.insert({_id:5, sessions: [ { sid: "foo"}, {sid:"bar", ssid:"test"}]});
> db.users.find();
{ "_id" : 4, "sessions" : [ { "sid" : "foo1" } ] }
{ "_id" : 5, "sessions" : [ { "sid" : "foo" }, { "sid" : "bar", "ssid" : "test" } ] }

> db.users.update({}, {"$pull": {sessions: {"sid" : "bar"}}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 0 })

then the $pull fails.

Umm. Your query matches both documents and you forgot the "multi" param. The update would work as expected if it matched the right document, or affected both. — Neil Lunn
– Neil Lunn, Commented Nov 10, 2014 at 3:49

JohnnyHK · Accepted Answer · 2014-11-10 03:49:46Z

1

Your $pull is correct, but you need to add the multi: true option for the update to apply to both docs:

db.users.update({}, {"$pull": {sessions: {"sid" : "bar"}}}, {multi: true});

answered Nov 10, 2014 at 3:49

JohnnyHK

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