As explained on the link, the nested documents are indexed as separate documents that reside in the segment next to the parent document. This way they can be identified as nested documents of that parent so it conceptually looks like the following in the index:
# First nested object
{
"comments.name": [ john, smith ],
"comments.comment": [ article, great ],
"comments.age": [ 28 ],
"comments.stars": [ 4 ],
"comments.date": [ 2014-09-01 ]
}
# Second nested object
{
"comments.name": [ alice, white ],
"comments.comment": [ like, more, please, this ],
"comments.age": [ 31 ],
"comments.stars": [ 5 ],
"comments.date": [ 2014-10-22 ]
}
# The root or parent document
{
"title": [ eggs, nest ],
"body": [ making, money, work, your ],
"tags": [ cash, shares ]
}
So in the index there are in fact 3 physical documents but only 1 logical document.
If you still have questions maybe you could reform you question to be more specific about what you are wanting to understand?