Here below show my code. I have to calculate the how many times distinct value repeated. Here i have store distinct value in "results".I used collection.count() to calculate but it's not work. please any one tell me where i have to mistake. Thank you very much .
var DistinctIntoSingleDB = function(Collection,arr,opt,distVal,callback){
Collection.find({}).distinct(distVal, function(err, results) {
if(!err && results){
console.log("Distinct Row Length :", results.length);
var a,arr1 = [];
for(var j=0; j<results.length; j++){
collection.count({'V6': results[j]}, function(err, count) {
console.log(count)
});
arr1.push(results[j]+ " : " +a);
}
callback(results,arr1);
}else{
console.log(err, results);
callback(results);
}
});
To get occurrences of distinct values of a field 'field1' on a collection 'col1' and write to a separate collection 'distinctCount'. Also allow to use disk space in case the collection is huge.
db.col1.aggregate(
[{$group: {
_id: "$field1",
count: { $sum : 1 }
}}, {
$group: {
_id: "$_id",
count: { $sum : "$count" }
}},{
$out: "distinctCount"
}],
{allowDiskUse:true}
)
While .distinct() works well for just obtaining the distinct values for a field, in order to actually get the counts of occurrences, this is better suited to the aggregation framework:
Collection.aggregate([
{ "$group": {
"_id": "$field",
"count": { "$sum": 1 }
}}
],function(err,result) {
});
Also the .distinct() method does "abstract" from where the specified "distinct" field is actually within an array. In this case you need to call $unwind first to process the array elements here:
Collection.aggregate([
{ "$unwind": "$array" },
{ "$group": {
"_id": "$array.field",
"count": { "$sum": 1 }
}}
],function(err,result) {
});
So the main work is basically done in the $group by "grouping" on the field values, which means the same thing as "distinct". The $sum is a grouping operator which in this case just adds up 1 for each occurrence of that value in the field for that collection.
