Group by date in mongoose/mongodb? - node.js

Question

Note: Mongo version 3.6.2.
I have a document that looks like this:
const Ticket = new mongoose.Schema({
event_id: [
{
required: false,
type: mongoose.Schema.Types.ObjectId,
ref: 'Event'
}
],
ticket_type: String,
createdAt: String,
}, { collection: 'tickets' });
I want to do a mongodb groupBy on ticket_type and createdAt where an event_id = X. So the output should like this:
[{ ticket_type: 'VIP', date: 2011-11-11, count: 12}, {..}]
The hard part is that createdAt is stored as timemillis in a string, ex:
{
_id : ObjectId(123),
ticket_type: 'VIP',
createdAt: '1233434',
event_id: [ObjectId(345)]
}
The answer should look something like this:
Ticket.find({ event_id: req.params.event_id }, function(err, tickCount) {
if (err) {
console.log(err);
} else {
res.json(tickCount);
}
});
Any help is greatly appreciated. Thanks.
This is what I came up with:
Ticket.aggregate([
{ $match: { event_id: ObjectId(req.body.event_id)} },
{
$addFields: {
"createdAt": {
$reduce: {
"input": {
$map: { // split string into char array so we can loop over individual characters
"input": {
$range: [ 0, { $strLenCP: "$createdAt" } ] // using an array of all numbers from 0 to the length of the string
},
"in":{
$substrCP: [ "$createdAt", "$$this", 1 ] // return the nth character as the mapped value for the current index
}
}
},
"initialValue": { // initialize the parser with a 0 value
"n": 0, // the current number
"sign": 1, // used for positive/negative numbers
"div": null, // used for shifting on the right side of the decimal separator "."
"mult": 10 // used for shifting on the left side of the decimal separator "."
}, // start with a zero
"in": {
$let: {
"vars": {
"n": {
$switch: { // char-to-number mapping
branches: [
{ "case": { $eq: [ "$$this", "1" ] }, "then": 1 },
{ "case": { $eq: [ "$$this", "2" ] }, "then": 2 },
{ "case": { $eq: [ "$$this", "3" ] }, "then": 3 },
{ "case": { $eq: [ "$$this", "4" ] }, "then": 4 },
{ "case": { $eq: [ "$$this", "5" ] }, "then": 5 },
{ "case": { $eq: [ "$$this", "6" ] }, "then": 6 },
{ "case": { $eq: [ "$$this", "7" ] }, "then": 7 },
{ "case": { $eq: [ "$$this", "8" ] }, "then": 8 },
{ "case": { $eq: [ "$$this", "9" ] }, "then": 9 },
{ "case": { $eq: [ "$$this", "0" ] }, "then": 0 },
{ "case": { $and: [ { $eq: [ "$$this", "-" ] }, { $eq: [ "$$value.n", 0 ] } ] }, "then": "-" }, // we allow a minus sign at the start
{ "case": { $eq: [ "$$this", "." ] }, "then": "." }
],
default: null // marker to skip the current character
}
}
},
"in": {
$switch: {
"branches": [
{
"case": { $eq: [ "$$n", "-" ] },
"then": { // handle negative numbers
"sign": -1, // set sign to -1, the rest stays untouched
"n": "$$value.n",
"div": "$$value.div",
"mult": "$$value.mult",
},
},
{
"case": { $eq: [ "$$n", null ] }, // null is the "ignore this character" marker
"then": "$$value" // no change to current value
},
{
"case": { $eq: [ "$$n", "." ] },
"then": { // handle decimals
"n": "$$value.n",
"sign": "$$value.sign",
"div": 10, // from the decimal separator "." onwards, we start dividing new numbers by some divisor which starts at 10 initially
"mult": 1, // and we stop multiplying the current value by ten
},
},
],
"default": {
"n": {
$add: [
{ $multiply: [ "$$value.n", "$$value.mult" ] }, // multiply the already parsed number by 10 because we're moving one step to the right or by one once we're hitting the decimals section
{ $divide: [ "$$n", { $ifNull: [ "$$value.div", 1 ] } ] } // add the respective numerical value of what we look at currently, potentially divided by a divisor
]
},
"sign": "$$value.sign",
"div": { $multiply: [ "$$value.div" , 10 ] },
"mult": "$$value.mult"
}
}
}
}
}
}
}
}
}, {
$addFields: { // fix sign
"createdAt": { $multiply: [ "$createdAt.n", "$createdAt.sign" ] }
}
},
{
$group: {
_id: {
ticket_type: "$ticket_type",
createdAt: { $dateToString: { format: "%Y-%m-%d", date: { $add: [ new Date(0), "$createdAt" ] }} },
count: { $sum: 1 }
}
}
},
{ $sort: { "createdAt": 1 } }
], function(err, tickCount) {
if (err) {
console.log(err);
} else {
res.json(tickCount);
}
});

Answer 1

You can use $group aggregation pipeline stage. To convert string to number you can use $toLong operator and then you can use $add (works for ISODate as well) to add that value to the date with zero miliseconds (new Date(0)) to get ISODate. Try:
Ticket.aggregate([
{ $match: { event_id: req.params.event_id } },
{
$group: {
_id: {
ticket_type: "$ticket_type",
createdAt: { $add: [ new Date(0), { $toLong: "$createdAt" } ] }
}
}
}
], function(err, tickCount) {
if (err) {
console.log(err);
} else {
res.json(tickCount);
}
});
EDIT: assuming that you manually converted string to number you can run following query to aggregate on date part of ISODate:
db.col.aggregate([
{ $match: { event_id: req.params.event_id } },
{
$group: {
_id: {
ticket_type: "$ticket_type",
createdAt: { $dateToString: { format: "%Y-%m-%d", date:{ $add: [ new Date(0), "$createdAt" ] } } },
count: { $sum: 1 }
}
}
},
{ $sort: { "_id.createdAt": 1 } }
])