Retrieve elements using $slice - php

Question

My result is following after executing find() query.
{
"_id" : ObjectId("5384928a03ea2e75268b4567"),
"0" : {
"name" : "mango",
"quantity" : "10"
},
"1" : {
"name" : "apple",
"quantity" : "14"
},
"2" : {
"name" : "banana",
"quantity" : "11"
},
"3" : {
"name" : "grapes",
"quantity" : "19"
},
"4" : {
"name" : "lichi",
"quantity" : "13"
},
"5" : {
"name" : "orange",
"quantity" : "10"
},
"6" : {
"name" : "lemon",
"quantity" : "10"
},
"7" : {
"name" : "pear",
"quantity" : "10"
},
"8" : {
"name" : "cherry",
"quantity" : "10"
},
"9" : {
"name" : "kiwi",
"quantity" : "10"
}
}
Now i want only any five elements in result(like from 2nd element to 6th element).
How to do this using $slice or is there any other method to retrieve only five elements in result?

Answer 1

The important thing here is, do you actually have an array for $slice to work on? There seems to be a bit of a misconception here common to people working with PHP as the way that language typically represents an array.
The mongo shell ( for example ) will show the clear distinction, where an array actually looks like this in it's JSON representation:
{
"_id" : ObjectId("5384928a03ea2e75268b4567"),
"arrayField": [
{
"name" : "mango",
"quantity" : "10"
},
{
"name" : "apple",
"quantity" : "14"
},
{
"name" : "banana",
"quantity" : "11"
},
{
"name" : "grapes",
"quantity" : "19"
}
]
}
That structure can use the $slice operator to return the elements you want. As an example here, 2 documents from index position 1
db.collection.find({},{ "arrayField": { "$slice": [ 1,2] }})
{
"_id" : ObjectId("5384928a03ea2e75268b4567"),
"arrayField" : [
{ "name" : "apple", "quantity" : "14" },
{ "name" : "banana", "quantity" : "11" }
]
}
The structure you are showing is just a bunch of key names for sub-documents within the top level document. It is probably a mistake but you just specify those fields in the projection. It's not an array so $slice does not apply:
db.collection.find({}, { "1": 1, "2": 1, "3": 1, "4": 1, "5": 1, "6": 1 })
But that probably is not what you want, so it looks like you will need to fix your data so it is an array.

Answer 2

$slice is used to control the number of elements in an array returned by the query, but I don't see an explicit array in your results. Your document should look something like:
{
"_id" : ObjectId("5384928a03ea2e75268b4567"),
"fruit" : [
{
"name" : "mango",
"quantity" : "10"
},
{
"name" : "apple",
"quantity" : "14"
}
]
}
Then you could query it with something like:
db.collection.find({},{"fruit": {$slice:[1:6]}})

Answer 3

If you want to get only 5 record from document you can use limit(), if you want to skip few of the record then use skip().
For Example :
db.collection.find().skip(2).limit(5);
This query fetch 5 documents after first 2 documents.