PHP MongoDB remove document and return it

Question

Is there something like findAndModify() but for remove() in mongodb. I need to remove a document and in the same time to retrieve its contents. I`m searching for a solution that does it in one "query" to the mongodb server. Thanks.

Can you please explain why you can not simply use two commands? Is there some other considerations that you have not mentioned? — Lix
– Lix, Commented Dec 10, 2013 at 13:41
Im making a logging feature and i need the previous and new state of the document. In this case i already have an identifier of the document i want to remove. Im looking for a concrete solution like this because i`m trying to optimize as much as possible because this will be done on all of the remove "queries" in the application — gprusiiski
– gprusiiski, Commented Dec 10, 2013 at 13:46
Since reads are concurrent as much as they like reading won't be a burden to you, deleting will, the biggest problem you might have is atomicity whereby you have to read separate to the delete in which case you might not get the true state, in which case you can use a deleted flag for all write operations and then remove the document later via cronjob or something — Sammaye
– Sammaye, Commented Dec 10, 2013 at 13:48
Yes, this is a possible solution, but i risk data integrety, ill have to modify my application not to use documents which have delete flag. It seems that ill have to use select (synchronous (puke)) :D Thanks — gprusiiski
– gprusiiski, Commented Dec 10, 2013 at 13:52

jmikola · Accepted Answer · 2014-01-02 16:25:15Z

3

MongoDB's findAndModify command supports a remove option. It is mutually exclusive with the update option, so you would specify remove instead of providing update with a "new object" (atomic modifiers or a replacement document). Also, while the new option would normally allow you to return the document in its pre- or post-update state, it doesn't apply to remove.

answered Jan 2, 2014 at 16:25

jmikola

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Lix · Accepted Answer · 2013-12-10 13:41:18Z

0

I do not believe that mongo has this functionality. I also don't really see why you would need this. If you identify your documents correctly (and use indexes where possible), the remove action will be very quick and very efficient.

However, once you have retrieved the document you want to remove, you can use it's _id attribute to find it again for removal.

var doc = db.data.find( { "please": "delete me" } );
db.data.remove( { "_id": doc._id } );

Mongo indexes your collections by _id as a default, so when you use it to identify a document (as we are doing with remove), the actual operation is very efficient.

answered Dec 10, 2013 at 13:41

Lix

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2 Comments

jmikola Over a year ago

findAndModify does support remove, which I mentioned in this answer. It does serve a purpose, as you can't be completely sure that the document (or even the criteria) will not change between the find() and remove() operations in your example.

Kevin Beal Over a year ago

doesn't .find() return an array of objects? Wouldn't that make doc._id = doc[0]._id or something like that?

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