Fetch documents only when field values are specified - mongodb

Question

I need help with writing dynamic queries in mongo shell.
function(a, obj){
db.courseContent.aggregate({$match: {Actor: a, ObjectId: obj}})
}
In the above function, I sometimes do not pass either a or obj.
I want the function to return documents of respective values.
If both a & obj are passed it should return documents matching both a
& obj but not with matching either 'a' or 'obj'
Can someone help me on this?

Answer 1

The $and operator is what you need here, to match on all the submitted values; the query you want will look something like this:
{$match: {$and: [Actor: a, ObjectId: obj]}}
You can dynamically put together a query like that without too much bother, perhaps like this:
function(a, b, c, d, e, f, g, h){
var match = [];
if (a) { match.push( {Alpha: a} ); }
if (b) { match.push( {Bravo: b} ); }
if (c) { match.push( {Charlie: c} ); }
if (d) { match.push( {Delta: d} ); }
if (g) { match.push( {Echo: e} ); }
if (e) { match.push( {Foxtrot: f} ); }
if (f) { match.push( {Gamma: g} ); }
if (h) { match.push( {Hotel: h} ); }
db.courseContent.aggregate([{$match: {$and: match}}])
}

Answer 2

Generic code which might work for you
function(valuearray,keyarray){
var and={};
and.$and=[];
var obj={};
for(var i=0;i<valuearray.length;i++){
if(valuearray[i]!=undefined && valuearray[i]!=''){
obj[keyarray[i]]=valuearray[i];
and.$and.push(obj);
}
}
db.courseContent.aggregate({$match:and});
}

Answer 3

Try This:
function(a, obj){
if(a!='' && a!=undefined && obj!='' && obj!=undefined){
db.courseContent.aggregate({$match:{$and:[{Actor: a, ObjectId: obj}]}});
}
else if(a!='' && a!=undefined){
var obj={};
var $match={};
var finalobj={};
finalobj["Actor"]=a;
obj["$match"]=finalobj;
db.courseContent.aggregate(obj);
}
else if(obj!='' && obj!=undefined){
var obj={};
var $match={};
var finalobj={};
finalobj["ObjectId"]=obj;
obj["$match"]=finalobj;
db.courseContent.aggregate(obj);
}
}