Model is
const mongoose = require('mongoose')
const Schema = mongoose.Schema
var UserActivitySchema = new Schema({
author: {type: mongoose.Schema.Types.ObjectId, required: true, unique: true, ref: 'user'},
readHistory: [{articleid: {type: mongoose.Schema.Types.ObjectId, ref: 'article'}, date_read: {type: Date, default: Date.now()}}],
watchHistory: [{videoid: {type: mongoose.Schema.Types.ObjectId, ref: 'video'}, date_watch: {type: Date, default: Date.now()}}],
searchHistory: [{query: String, date:{type: Date, default: new Date()}}]
})
module.exports = mongoose.model('useractivity',UserActivitySchema, 'useractivities')
Here i want to fetch readHistory for which i have used query
if (req.query.page) var page = parseInt(req.query.page);
else var page = 1;
UserActivity.findOne({author: req.client.userId}).select('readHistory')
.populate({path: 'readHistory.articleid', select: 'title description views thumbnailURI', options: { skip: (page-1)*10, limit: 10}, populate: {path: 'author', select: 'displayName -_id'}})
.exec().then(activity=>{
if (!activity || activity.readHistory.length <= 0)
res.json({success: false, message: 'You have not read any article yet.'})
else {
res.json({success: true, readHistory: activity.readHistory})
}
}).catch(err=>{
res.json({success: false, message: err.message})
})
but it returns all the document in the array. How fix this?
populate()that needs the "limit" here, but the "array". You instead$sliceto project a "page" of itemsfindOne({author: req.client.userId}).select({ 'readHistory': { '$slice': [ (page-1)*10, 10 ] }).populate(...)with everything except theoptionssince the$sliceis already there. The alternate case is about actually "limiting joins", which is a little more involved and not actually whatpopulate()does, since it's not a "join" but another query retrieving data.}in theselect()of that example, but you should get the idea. Note also that the terms "skip" and "limit" are even used in the$slicedocumentation, since this was the original purpose of the operator way back in the original MongoDB design.