Query for boolean field as "not true" (e.g. either false or non existent)

Question

I'm sure I'm missing something very basic in MongoDB queries, can't seem to get this simple condition.

Consider this collection

> db.tests.find() { "_id" : ObjectId("..."), "name" : "Test1" , "deleted" : true} { "_id" : ObjectId("..."), "name" : "Test2" , "deleted" : false} { "_id" : ObjectId("..."), "name" : "Test3" } 

I would simply like to query all the items that are "not deleted"

I know how to find the item that has a "deleted" flag set to true:

> db.tests.find({deleted:true}) { "_id" : ObjectId("..."), "name" : "Test1" , "deleted" : true} 

But how do I find all items that are NOT "deleted" (e.g. negate the above query, or in other words, any items that either doesn't have a "deleted" field, or have it with value false

What I tried by guessing (please don't laugh...)

> db.tests.find({$not : {deleted: true}}) 

(returns no results)

> db.tests.find({$not : {$eq:{deleted:true}}}) 

error: { "$err" : "invalid operator: $eq", "code" : 10068 }

> db.tests.find({deleted:{$not: true}}) 

error: { "$err" : "invalid use of $not", "code" : 13041 }

> db.tests.find({deleted:{$not: {$eq:true}}}) 

error: { "$err" : "invalid use of $not", "code" : 13034 }

What am I missing?

Answer 1

db.tests.find({deleted: {$ne: true}}) 

Where $ne stands for "not equal". (Documentation on mongodb operators)

Answer 2

For the sake of completeness, another way to do this is with $in:

db.test.find({deleted: {$in: [null, false]}}) 

Including null in the array pulls in the docs where the deleted field is missing. This query can use an index on {deleted: 1} in the current 2.6.6 MongoDB release.