how to do a mysql query
SELECT COUNT(DISTINCT ip), COUNT(DISTINCT area) FROM visit_logs GROUP BY t_hour
in mongodb without multi mapreduct?
You have to keep the list of "keys" in your objects, and compute your count as the count of the distinct keys; this can be done in the finalize method in MongoDb's map/reduce.
Something like (untested):
var mapFn = function() {
emit(this.t_hour, { ips: [this.ip], areas: [this.area] );
};
var reduceFn = function(key, values) {
var ret = { ips: {}, areas: {} };
// objects used as "sets"
var ips = {};
var areas = {};
values.forEach(function(value) {
value.ips.forEach(function(ip) {
if (!ips[ip]) {
ips[ip] = true; // mark as seen
ret.ips.push(ip);
}
});
value.areas.forEach(function(area) {
if (!areas[area]) {
areas[area] = true; // mark as seen
ret.areas.push(area);
}
});
});
};
var finalizeFn = function(key, value) {
return { ips: value.ips.length; areas: value.areas.length };
}
Related
I'm trying to find a certain document in my mongodb then update the int value of it using find query, I'm using $in because I used an array to find each element inside it, but when I used ObjectId it gives me error:
bloodinventoryDocs is not iterable
Here is what I did
var mongoose = require('mongoose');
var id = mongoose.Types.ObjectId('5c014c999cc48c3b0057988b');
var newValue = 1;
var newBloodgroup = "A_positive";
var newGetbloodcomponent = "Whole Blood";
Bloodinventory.find({ blood_component : { $in : newGetbloodcomponent} , blood_group: { $in :newBloodgroup},chapter: { $in :id}}, function(err, bloodinventoryDocs) {
for(let bloodinventory of bloodinventoryDocs) {
bloodinventory.num_stock = bloodinventory.num_stock + newValue ;
bloodinventory.save(function(err) {
if (err) {
console.log(err);
} else {
console.log('success');
}
});
}
});
Just use chapter: { $in: [id] }
i am trying to push the resultant of the count to an array in mogodb query, while pushing it showing the array after that if print it outside of query it is showing empty array.
collection1 in db is like below
[{title:Home,
date:24-10-2016},
{title:Accesories,
date:13-02-2016}
]
my code
exports.listOfCategories=function(req,res){
collection1.find().exec(function (err, categories) {
if (err) {
return res.status(400).send({
message: errorHandler.getErrorMessage(err)
});
} else {
var categoryList = categories;
var catTitle;
var allCat = [];
// console.log(categoryList);
for (var i = 0; i < categoryList.length; i++) {
catTitle = categoryList[i].title;
contentCounts(catTitle);
function contentCounts(content, callback) {
var catName = new RegExp(content, 'i');
var mongoQuery = {
"ProCategory.title": catName
}
collection2.find(mongoQuery).count(function (err, count) {
generateContentArr(content, count)
});
}
function generateContentArr(content, count) {
allCat.push({
name: content,
count: count
});
console.log(JSON.stringify(allCat));
// Here it is showing the array what i pushed
}
}
console.log(JSON.stringify(allCat));
// Here it not showing the total array, it showing an empty array
res.json(allCat);
}
});
}
Thanks in advance
You are not waiting for the result of an async operation, in your case in the for loop you need to wait for the result of mongo operation, but as for loop is synchronous, you are just making calls to mongo but don't wait for the results, and print the empty array right after the loop.
I would suggest you to use promises instead of callbacks, I don't know which version of mongoose you are using but the last version have promise support for mongo methods like find and count. Here is an example for your case:
var Promise = require("bluebird");
function countByTitle(catTitle){
var mongoQuery = {"ProCategory.title": new RegExp(catTitle, 'i')}
return collection2.count(mongoQuery).then(function(count) {
return {
name: catTitle,
count: count
};
});
}
collection1.find().then(function (categories) {
var categoryList = categories;
var promises = [];
for (var i = 0; i < categoryList.length; i++) {
promises.push(countByTitle(categoryList[i].title));
}
return Promise.all(promises).then(results => {
console.log(JSON.stringify(results));
})
}).catch(function (err) {
//if there is any error while resolving the promises, this block will be called
return res.status(400).send({
message: errorHandler.getErrorMessage(err)
});
});
I have mongodb in which there is 3 huge collections say 'A', 'B' and 'C'
Each collection contains about 2 million documents.
There are certain properties for each of the document.
Each document need to be updated based on those values of certain properties, from which i can determine what should be the '$set' to that document.
currently i am using the same approach for each collection.
that to find all documents in batches. collection them in memory (which i think the culprit for the current approach), then one by one update them all.
For the first collection(that have similar data as in other collections), it takes 10 minutes to get completed. then the next two collections taking 2 hours approx to get the task done or mongodb client get crashed earlier.
There is something wrong and no desired in the current approach.
Model.collection.find({}).batchSize(BATCH).toArray(function(err, docs){
if(err || !docs || !docs.length)
return afterCompleteOneCollection(err);
var spec = function(index) {
if(index % 1000 === 0) console.log('at index : ' + index);
var toSet = { };
var toUnset = { };
var over = function(){
var afterOver = function(err){
if(err) return afterCompleteOneCollection(err);
if(index < docs.length - 1) spec(index+1);
else afterCompleteOneCollection(null);
};
var sb = Object.keys(toSet).length;
var ub = Object.keys(toUnset).length;
if(sb || ub) {
var all = {};
if(sb) all.$set = toSet;
if(ub) all.$unset = toUnset;
Model.collection.update({ _id : docs[index]._id }, all, {}, afterOver);
} else afterOver(null);
};
forEachOfDocument(docs[index], toSet, toUnset, over);
};
spec(0);
});
Is there any better solution for the same.?
The streaming approach from here http://mongodb.github.io/node-mongodb-native/api-generated/cursor.html#stream worked for me
This is what i am doing :
var stream = Model.collection.find().stream();
stream.on('data', function(data){
if(data){
var toSet = { };
var toUnset = { };
var over = function(){
var afterOver = function(err){
if(err) console.log(err);
};
var sb = Object.keys(toSet).length;
var ub = Object.keys(toUnset).length;
if(sb || ub) {
var all = {};
if(sb) all.$set = toSet;
if(ub) all.$unset = toUnset;
Model.collection.update({ _id : data._id }, all, {}, afterOver);
} else afterOver(null);
};
forEachOfDocument(data, toSet, toUnset, over);
}
});
stream.on('close', function() {
afterCompleteOneCollection();
});
I have book and author collection.in this name and works_written are the same value column respectively.so i tried the following script but it emit only first map values,second map values not emitted.
book = function() {
emit(this.id, {name: this.name,editions:this.editions});
}
author = function() {
emit(this.id, {name:this.name,works_written: this.works_writtten,});
}
r_b = function(k, values) {
var result = {};
values.forEach(function(value) {
var name;
for (name in value) {
if (value.hasOwnProperty(name)) {
result[name] = value[name];
}
}
});
return result;
};
r_a = function(k, values) {
var result = {};
values.forEach(function(value) {
var works_written;
for (works_written in value) {
if (value.hasOwnProperty(works_written)) {
result[works_written] = value[works_written];
}
}
});
return result;
};
res = db.book.mapReduce(book, r_ja, {out: {reduce: 'joined'}})
res = db.author.mapReduce(author, r_jp, {out: {reduce: 'joined'}})
can someone help me out?
From looking at your code, it seems like you have two collections, "book" and "author". Each book is structured as
{
id: <some id>,
name: <some name>,
editions: <comma-separated string of editions>
}
and each author is structured as
{
id: <some id>,
name: <some name>,
works_written: <comma-separated string of works written>
}
It would be more reasonable to store both works_written and editions as arrays rather than comma-separated lists each packed into an individual string. This would make iterating over the array possible.
Additionally, do you have multiple documents for each author and each book? If not, you do not need a mapreduce to do what you are attempting to do - a simple find() should work.
In case I have misinterpreted, what exactly are you attempting to do?
Hello all I'm trying to do is to get the count of each distinct departmentType:
fnMap = function() {
emit(this.departments.departmentType, {typeCount:1} );
}
fnReduce = function(key, values) {
var result = {typeCount: 0};
values.forEach(function(value) {
result.typeCount += value.brandCount;
});
return result;
};
var command = {
mapreduce : "clients",
query : {"departments.departmentType": {$exists: true}},
map : fnMap.toString(),
reduce : fnReduce.toString(),
//sort: {"departments.departmentType":1},
out: {inline: 1}
};
mongoose.connection.db.executeDbCommand(command, function(err, dbres) {
});
When executing the command, dbres.documents[0].results only contains 1 item with the total number of departmentTypes, instead of several items one for each departmentType with its count.
Any ideas what am I doing wrong?
Also, when I uncomment the SORT line, I get error "db assertion failure: could not create cursor over...", I believe the field name is written correctly.
Mongoose v3 has now a Model.mapreduce() function (see doc).
The full example shown is:
var o = {};
o.map = function () { emit(this.name, 1) }
o.reduce = function (k, vals) { return vals.length }
o.out = { replace: 'createdCollectionNameForResults' }
o.verbose = true;
User.mapReduce(o, function (err, model, stats) {
console.log('map reduce took %d ms', stats.processtime)
model.find().where('value').gt(10).exec(function (err, docs) {
console.log(docs);
});
})
The problem with count i believe is because in your fnReduce() function you are summit the results instead of displaying them in an array.
You can use:
db.clients.distinct("departments.departmentType")
That will give an array with all the distinct departmentType values.
There were two problems in your map/reduce. One is brandCount in reduce rather than typeCount. But more importantly, you are trying to emit once per document, when you need to emit once per department array element. Corrected (and slightly simplified) code:
> fnMap = function () {
this.departments.forEach(
function (d) {
emit(d.departmentType, 1);
}
);
}
> fnReduce = function (key, values) {
var result = 0;
values.forEach(
function (value) {result += value;});
return result;
}