MongoDB Query Find multiple fields or documents properly - mongodb

Question

In my collection I got two fields, gender and country.
In the gender field they are all "female" and each of them are in different country.
I tried to query the collection:
return Meteor.users.find(
{
_id: {$ne: Meteor.userId()},
$or: [ { "country": "Australia" }, { "gender": "" } ]
}).fetch();
The result goes like this:
When set the gender to "null" or empty it gives me all the user who are in Australia.
But when I set gender to "female" and country to "Australia" it gives me all the female users from different countries which is supposed to be only female from Australia. It seems it ignores first argument which is the country.
Is there a way to have it more accurate? Please help thank you.
My Goal is:
To make the database query more accurately and bw able to adopt to the changes.
Example:
Going back to the issue above, when I added the "gender" on the search query, it should only look for female users whose country is Australia. Not all females from different countries.

Answer 1

Since you need to meet both the conditions female as well as country, it should be and
return Meteor.users.find({ _id: {$ne: Meteor.userId()},
$and: [{"country": "Australia"},
{"gender": "female"}]
}).fetch();

Answer 2

This might not be the perfect solution, but you can do something like this:
var filter = { };
filter._id = { $ne: Meteor.userId() };
if(Meteor.country()){
filter.country = Meteor.country();
};
if(Meteor.gender()){
filter.gender = Meteor.gender();
};
return Meteor.users.find(filter).fetch();
Also, since you don't know on what basis the query is to be performed, you shouldn't use operators like $and or $or
The query document that you prepared queries for all the users, where _id is not equal to Meteor.userId() AND country = AUSTRALIA or gender = FEMALE.
Also the solution that zangw suggested, there $and isn't required as all the criteria in the query document to the find method is implicitly ANDed.
Hope this helps.

Answer 3

I finally found out a solution on how to sort this out. It is a bit long code but it did the trick.
I scanned the data I got and remove null data, in my case above if gender is == to "" then ignore it else get its data if exist. I did it via loop.
Using array push I was able to insert object. Ex: If country is not null then:
variable.push('{"+objectPropertyName[i]+"'+':'+'"'+objectValue[i]+'"}');
The output of this looks like this:
["{"country":"Australia"}", "{"gender":"female"}"]
by parsing it to JSON then becomes an object.
Once all the objects necessary for the query is set the I can query the mongo through:
db.collection.find({"_id": {$ne: Meteor.userId()}, $and: **variable**}).fetch();
So far it works perfectly. :)