Test case for http://jira.mongodb.org/browse/SERVER-413

mongo_exists_with_index_spec.rb

require 'mongo'

describe "MongoDB" do
  before(:all) do
    @db = Mongo::Connection.new.db('test').collection('index_test')
    @db.drop
    @db.create_index( 'a' )
    @db.insert( { 'a' => 1 } )
    @db.insert( { 'b' => 1 } )
  end

  it "should find a record where indexed key does not exist" do
    @db.find_one( 'a' => { '$exists' => false } ).should_not be_nil
  end
  
  it "should find a record where indexed key exists" do
    @db.find_one( 'a' => { '$exists' => true } ).should_not be_nil
  end
  
  it "should find a record where unindexed key does not exist" do
    @db.find_one( 'b' => { '$exists' => false } ).should_not be_nil
  end
  
  it "should find a record where unindexed key exists" do
    @db.find_one( 'b' => { '$exists' => true } ).should_not be_nil
  end

end

output from mongo_exists_with_index_spec

MongoDB
- should find a record where indexed key does not exist (FAILED - 1)
- should find a record where indexed key exists (FAILED - 2)
- should find a record where unindexed key does not exist
- should find a record where unindexed key exists

1)
'MongoDB should find a record where indexed key does not exist' FAILED
expected not nil, got nil
./mongo_problem_spec.rb:14:

2)
'MongoDB should find a record where indexed key exists' FAILED
expected not nil, got nil
./mongo_problem_spec.rb:18:

Finished in 5.018523 seconds

4 examples, 2 failures

the same thing in mongo console

> db.index_test.drop()
{"nIndexesWas" : 2 , "msg" : "all indexes deleted for collection" , "ns" : "test.index_test" , "ok" : 1}
> db.index_test.ensureIndex({'a':1})
true
> db.index_test.save({'a':1})
> db.index_test.save({'b':1})
> db.index_test.find({'a':{$exists:true}})   
> db.index_test.find({'a':{$exists:false}})
> db.index_test.find({'b':{$exists:true}}) 
{"_id" :  ObjectId( "4afb1cf16dc9bf5d3b820748")  , "b" : 1}
> db.index_test.find({'b':{$exists:false}})
{"_id" :  ObjectId( "4afb1ced6dc9bf5d3b820747")  , "a" : 1}
>