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  1. Core Server
  2. SERVER-12266

Update no longer allows empty modifier objects

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    • Type: Icon: Bug Bug
    • Resolution: Done
    • Priority: Icon: Major - P3 Major - P3
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    • Affects Version/s: 2.5.4
    • Component/s: Write Ops
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    • ALL
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    • 3
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      tl;dr:

      There is no consistent way to upsert an identifier-only document between 2.4.x and 2.5.x. Allowing modifiers in a newObj to be an empty BSON object would help.

      I noticed the following while testing Doctrine ODM against 2.5.x. In 2.4.x and earlier versions, I believe there was only a single way to upsert a document that only contained an identifier field:

      > db.foo.update({_id:1}, {$set: {}}, true); db.getLastErrorObj();
{
	"updatedExisting" : false,
	"n" : 1,
	"connectionId" : 1,
	"err" : null,
	"ok" : 1
}
> db.foo.update({_id:2}, {}, true); db.getLastErrorObj();
{
	"updatedExisting" : false,
	"upserted" : ObjectId("52cb12553ad84dc22b80c72f"),
	"n" : 1,
	"connectionId" : 1,
	"err" : null,
	"ok" : 1
}
> db.foo.update({_id:3}, {$set: {_id:3}}, true); db.getLastErrorObj();
{
	"err" : "Mod on _id not allowed",
	"code" : 10148,
	"n" : 0,
	"connectionId" : 1,
	"ok" : 1
}
> db.foo.find()
{ "_id" : 1 }
{ "_id" : ObjectId("52cb12553ad84dc22b80c72f") }

      Using an empty object for the newObj argument results in the upsert ignoring the client-provided _id. $set cannot be used on _id, even if that would technically be OK for an upsert. $setOnInsert would make more sense, but it also doesn't work – it's also 2.4+ only, so I wouldn't rely on it for essential ODM logic.

      In 2.5.x, the one working method from 2.4.x no longer works. The two methods that didn't work in 2.4.x do work in 2.5.x:

      > db.foo.update({_id:1}, {$set: {}}, true); db.getLastErrorObj();
{
	"err" : "'$set' is empty. You must specify a field like so: {$mod: {<field>: ...}}",
	"code" : 16840,
	"n" : 0,
	"connectionId" : 2,
	"ok" : 1
}
> db.foo.update({_id:2}, {}, true); db.getLastErrorObj();
{
	"updatedExisting" : false,
	"upserted" : 2,
	"n" : 1,
	"connectionId" : 2,
	"syncMillis" : 0,
	"writtenTo" : null,
	"err" : null,
	"ok" : 1
}
> db.foo.update({_id:3}, {$set: {_id:3}}, true); db.getLastErrorObj();
{
	"updatedExisting" : false,
	"upserted" : 3,
	"n" : 1,
	"connectionId" : 2,
	"syncMillis" : 0,
	"writtenTo" : null,
	"err" : null,
	"ok" : 1
}
> db.foo.find()
{ "_id" : 2 }
{ "_id" : 3 }

      The strict validation that makes the 2.4.x solution no longer work looks to have been introduced in this commit for SERVER-7175.

            Assignee:
            scotthernandez Scott Hernandez (Inactive)
            Reporter:
            jmikola@mongodb.com Jeremy Mikola
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              Created:
              Updated:
              Resolved: