What is the best way to query an array of subdocument in MongoDB? - mongodb

Question

let's say I have a collection like so:
{
"id": "2902-48239-42389-83294",
"data": {
"location": [
{
"country": "Italy",
"city": "Rome"
}
],
"time": [
{
"timestamp": "1626298659",
"data":"2020-12-24 09:42:30"
}
],
"details": [
{
"timestamp": "1626298659",
"data": {
"url": "https://example.com",
"name": "John Doe",
"email": "john#doe.com"
}
},
{
"timestamp": "1626298652",
"data": {
"url": "https://www.myexample.com",
"name": "John Doe",
"email": "doe#john.com"
}
},
{
"timestamp": "1626298652",
"data": {
"url": "http://example.com/sub/directory",
"name": "John Doe",
"email": "doe#johnson.com"
}
}
]
}
}
Now the main focus is on the array of subdocument("data.details"): I want to get output only of relevant matches e.g:
db.info.find({"data.details.data.url": "example.com"})
How can I get a match for all "data.details.data.url" contains "example.com" but won't match with "myexample.com". When I do it with $regex I get too many results, so if I query for "example.com" it also return "myexample.com"
Even when I do get partial results (with $match), It's very slow. I tried this aggregation stages:
{ $unwind: "$data.details" },
{
$match: {
"data.details.data.url": /.*example.com.*/,
},
},
{
$project: {
id: 1,
"data.details.data.url": 1,
"data.details.data.email": 1,
},
},
I really don't understand the pattern, with $match, sometimes Mongo do recognize prefixes like "https://" or "https://www." and sometime it does not.
More info:
My collection has dozens of GB, I created two indexes:
Compound like so:
"data.details.data.url": 1,
"data.details.data.email": 1
Text Index:
"data.details.data.url": "text",
"data.details.data.email": "text"
It did improve the query performance but not enough and I still have this issue with the $match vs $regex. Thanks for helpers!

Answer 1

Your mistake is in the regex. It matches all URLs because the substring example.com is in all URLs. For example: https://www.myexample.com matches the bolded part.
To avoid this you have to use another regex, for example that just start with that domain.
For example:
(http[s]?:\/\/|www\.)YOUR_SEARCH
will check that what you are searching for is behind an http:// or www. marks.
https://regex101.com/r/M4OLw1/1
I leave you the full query.
[
{
'$unwind': {
'path': '$data.details'
}
}, {
'$match': {
'data.details.data.url': /(http[s]?:\/\/|www\.)example\.com/)
}
}
]
Note: you must scape special characters from the regex. A dot matches any character and the slash will close your regex causing an error.