Query running very slow on big MongoDB db - mongodb

Question

I have a MongoDB db with a single rather large collection of documents (13GB for about 2M documents) sitting on a single server with 8GB RAM. Each document has a text field that can be relatively large (it can be a whole blog post) and the other fields are data about the text content and the text author. Here's what the schema looks like:
{
text: "Last night there was a storm in San Francisco...",
author: {
name: "Firstname Lastname",
website_url: "http://..."
},
date: "201403075612",
language: "en",
concepts: [
{name: "WeatherConcept", hit: "storm", start: 23, stop: 28},
{name: "LocationConcept", hit: "San Francisco", start: 32, stop: 45}
],
location: "us",
coordinates: []
}
I'm planning to query the data in different ways:
Full-text search on the "text" field. So let's say my text search query is q:
db.coll.aggregate([
{
$match:{
$text: {
$search:q
}
}
}
])
Aggregate documents by author:
db.coll.aggregate([
{
$project: {
name: "$author.name",
url: "$author.website_url"
}
},
{
$group: {
_id: "$name",
size: {
$sum:1
},
url: {
$first: "$url"
}
}
},
{
$sort:{
size:-1
}
}
])
Aggregate documents by concepts:
db.coll.aggregate([
{
$unwind: "$concepts"
},
{
$group: {
_id: "$concepts.name",
size: {
$sum:1
}
}
},
{
$sort:{
size:-1
}
}
])
These three queries may also include filtering on the following fields: date, location, coordinates, language, author.
I don't have indexes yet in place, so the queries run very slow. But since the indexes would be very different for the different ways I hit the data, does that rule out indexing as a solution? Or is there a way to index for all these cases and not have to shard the collection? Basically my questions are:
What would be a good indexing strategy in this case?
Do I need to create separate collections for authors and concepts?
Should I somehow restructure my data?
Do I need to shard my collection or is my 8GB single-server powerful enough to handle that data?

Answer 1

Do you have any indexes on your collection?
Have a look at the following
http://docs.mongodb.org/manual/indexes/
if you do have indexes make sure they are being hit by doing the following
db.CollectionName.find({"Concept":"something"}).explain();
You also need to give us more information about your setup. How much RAM does the server have? I've worked with a MongoDB that has 200GB sitting on 3 shards. So 13GB on 1 shouldn't be an issue