I'm coding a mongoose schema so I need a list of possible field in my collection.
Please how can I display all fields names in a specific collection, thank you.
switch to the db you're using and type:
mr = db.runCommand({
"mapreduce" : "myCollectionName",
"map" : function() {
for (var key in this) { emit(key, null); }
},
"reduce" : function(key, stuff) { return null; },
"out": "myCollectionName" + "_keys"
})
once you get result, type:
db[mr.result].distinct("_id")
and you will get a list of fields names.
Related
Using MongoDB shell script 3.2, how can I update all fields where field names have a space replace those with underscore?
{
"Some Field": "value",
"OtherField" :"Value",
"Another Field" : "Value"
}
update the above document as below
{
"Some_Field": "value",
"OtherField" :"Value",
"Another_Field" : "Value"
}
rename field can be done with something like this
db.CollectionName.update( { _id: 1 }, { $rename: { 'nickname': 'alias', 'cell': 'mobile' } } )
Challenging part here is filter, how to come up with a filter where there is a space in field name
This needs a two-step approach. First, you need a mechanism to get a list of all the keys with a space in your collection. Once you get the list, construct an object that maps those keys to their renamed values. You can then use that object as your $rename operator document. Consider using mapReduce to get the list of keys with spaces.
The following mapReduce operation will populate a separate collection with all the filtered keys as the _id values:
mr = db.runCommand({
"mapreduce": "CollectionName",
"map": function() {
var regxp = /\s/;
for (var key in this) {
if (key.match(regxp)) {
emit(key, null);
}
}
},
"reduce": function() {},
"out": "filtered_keys"
})
To get a list of all the spaced keys, run distinct on the resulting collection:
db[mr.result].distinct("_id")
["Some Field", "Another Field"]
Now given the list above, you can assemble your update document by creating an object that will have its properties set within a loop. Normally your update document will have this structure:
var update = {
"$rename": {
"Some Field": "Some_Field",
"Another Field": "Another_Field"
}
}
Thus
var update = { "$rename": {} };
db[mr.result].distinct("_id").forEach(function (key){
update["$rename"][key] = key.replace(/ /g,"_");
});
which you can then use in your update as
db.CollectionName.update({ }, update, false, true );
Thanks to #chridam that was a excellent query.
Had to make small changes to run query, Full working query.
mr = db.runCommand({
"mapreduce": "MyCollectionName",
"map": function() {
var regxp = /\s/;
for (var key in this) {
if (key.match(regxp)) {
emit(key, null);
}
}
},
"reduce": function() {},
"out": "filtered_keys"
})
db[mr.result].distinct("_id")
var update = { "$rename": {} };
db[mr.result].distinct("_id").forEach(function (key){
update["$rename"][key] = key.replace(/\s+/g, "_");
});
//print(update)
db.MyCollectionName.update({ }, update, false, true );
I'm attempting to write a find query where one of the keys is unknown at the time the query is run, for example on the following document I'm interested in returning the document if "setup" is true:
{
"a": {
"randomstringhere": {
"setup": true
}
}
}
However I can't work how to wildcard the "randomstringhere" field as it changes for each document in the collection.
Can somebody help?
There is not much you can do with that. But you can modify your collection schema like
{
"a": [
{
"keyName": "randomstringhere",
"setup": true
},
//...
]
}
you can than write query to look
{
'a' : { $elemMatch: { setup: true } ,
}
You can't do this with a single query, as with the current design you would need a mechanism to get all the random keys that you need and then assemble the query document that uses the $or operator in the event that you get a list of variable key name.
The first part of your operation is possible using Map-Reduce. The following mapreduce operation will populate a separate collection called collectionKeys with all the random keys as the _id values:
mr = db.runCommand({
"mapreduce": "collection",
"map" : function() {
for (var key in this.a) { emit(key, null); }
},
"reduce" : function() { },
"out": "collectionKeys"
})
To get a list of all the random keys, run distinct on the resulting collection:
db[mr.result].distinct("_id")
Example Ouput
["randomstring_1", "randomstring_2", "randomstring_3", "randomstring_4", ...]
Now given the list above, you can assemble your query by creating an object that will have its properties set within a loop. Normally your query document will have this structure:
var query = {
"$or": [
{ "a.randomstring_1.setup": true },
{ "a.randomstring_2.setup": true },
{ "a.randomstring_3.setup": true }
]
};
which you can then use in your query:
db.collection.find(query)
So using the above list of subdocument keys, you can dynamically construct the above using JavaScript's map() method:
mr = db.runCommand({
"mapreduce": "collection", // your collection name
"map" : function() { // map function
for (var key in this.a) { emit(key, null); }
},
"reduce" : function() { }, // empty reducer that doesn't do anything
"out": "collectionKeys" // output collection with results
})
var randomstringKeysList = db[mr.result].distinct("_id"),
orOperator = randomstringKeysList.map(function (key){
var o = {};
o["a."+ key +".setup"] = true;
return o;
}),
query = { "$or": orOperator };
db.collection.find(query);
I wants to get records with all fields using $group in mongodb.
i.e: SELECT * FROM users GROUP BY state, equivalent query in mongodb.
Can any one help me.
AFAIK there is no way to return all object in group query. You can use $addToSet operator to add fields into the array to return. The example code is shown in the below. You can add all the fields to the array using addToSet operator. It will return array as a response and you should get data from those array(s).
db.users.aggregate({$group : {_id : "$state", id : {$addToSet : "$_id"}, field1 : {$addToSet : "$field1"}}});
You can do it with MapReduce instead:
db.runCommand({
mapreduce: 'tests',
map: function() {
return emit(this.state, { docs: [this] });
},
reduce: function(key, vals) {
var res = vals.pop();
vals.forEach(function(val) {
[].push.apply(res.docs, val.docs);
});
return res;
},
finalize: function(key, reducedValue) {
return reducedValue.docs;
},
out: { inline: 1 }
})
I'm using finalize function in my example because MapReduce not supports arrays in reducedValue.
But, regardless of the method, you should try to avoid such queries in productions. They are fine for rare requests, like analytics, db migrations or daily scripting, but not for frequent ones.
I'm using MongoDB and the node-mongodb-native driver.
I'm trying to return all records with a distinct attribute.
This seems to work, however it only returns the value which I'm checking for being distinct, not all values in each document.
This is what I have tried to return just the name field, I've also tried without it and variations of, but it always only returns the item_id's in an array.
this.collection.distinct("item_id", [{"name" : true}, {sold : {"$exists" : true}}], function(err, results) {
if (err) {
callback(err);
} else {
console.log(results);
}
});
Any suggestions how to get all the data from each document?
Thank you!
EDIT: Using Map Reduce
So, I just setup the start of a map reduce, using the node-mongodb-native, here's what I have so far:
var map = function() {
emit(this._id, {"_id" : this._id, "name" : this.name});
}
var reduce = function(key, values) {
var items = [];
values.forEach(function(v) {
items.push(v);
});
return {"items" : items};
}
this.collection.mapReduce(map, reduce, {out: "res"}, function(err, results) {
if (err) {
console.log(err);
} else {
console.log(results);
}
});
I know the logic isn't in there for distinct, but the results is the db object, I can't use 'toArray' on it. Any ideas why this might be?
I have this document stored in mongodb document:
{
"_id":ObjectId("4eb7642ba899edcc31000001")
"hash":"abcd123"
"value":"some_text_here"
}
I am using NodeJS to access the database:
collection.findOne({'hash' : req.param('query') },
function(err, result){
console.log(res);
});
The result of this query is the whole document, however I need to get only the "value" text: "some_text_here"
How can this be done?
You can specify the fields that you are interested in (_id will always be returned, though):
collection.findOne({'hash': req.param('query') },
{fields: ['value'] },
callbackFunction );
You can do it such way:
collection.findOne({'hash' : req.param('query') },
function(err, result){
console.log(result.value);
});