Mongodb pull data from subarray - mongodb

Question

Hi I have below mongodb collection
{
"_id" : ObjectId("53ce993639203f573671d3f5"),
"user_id" : NumberLong(51),
"buses" : [
{
"slot_id" : NumberLong(50),
"status" : NumberLong(3),
"bus_id" : NumberLong(8)
},
{
"slot_id" : NumberLong(67),
"status" : NumberLong(3),
"bus_id" : NumberLong(12)
}
]
}
i want to pull sub array where bus_id=8.
Final result i want to be like this
{
"_id" : ObjectId("53ce993639203f573671d3f5"),
"user_id" : NumberLong(51),
"buses" : [
{
"slot_id" : NumberLong(67),
"status" : NumberLong(3),
"bus_id" : NumberLong(12)
}
]
}
When i tried with below query
db.collectionname.update({},{$pull: {buses: {bus_id:8}}},{multi: true})
I got below error in console,
Cannot apply $pull/$pullAll modifier to non-array
Can any one please suggest me how to achieve this,and also need php mongodb query also.
Thanks in Advance

Answer 1

Worked fine for me for your sample document:
> db.bus.findOne()
{
"_id" : ObjectId("53ce993639203f573671d3f5"),
"user_id" : NumberLong(51),
"buses" : [
{
"slot_id" : NumberLong(50),
"status" : NumberLong(3),
"bus_id" : NumberLong(8)
},
{
"slot_id" : NumberLong(67),
"status" : NumberLong(3),
"bus_id" : NumberLong(12)
}
]
}
> db.bus.update({}, { "$pull" : { "buses" : { "bus_id" : 8 } } }, { "multi" : true })
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.bus.findOne()
{
"_id" : ObjectId("53ce993639203f573671d3f5"),
"user_id" : NumberLong(51),
"buses" : [
{
"slot_id" : NumberLong(67),
"status" : NumberLong(3),
"bus_id" : NumberLong(12)
}
]
}
The cause of the problem is that some buses element is not an array. What does the query
> db.bus.find({ "buses.0" : { "$exists" : 0}, "buses" : { "$ne" : [] } })
return? This query finds documents where there is no 0th element of the array and the array is not empty, so it should return documents where buses is not an array.