Pouchdb view returning empty result - database

Question

Good morning,
I'm currently working with Couchdb and Pouchdb and I'm having a problem with one query on Pouchdb side.
I have a database with different documents setup like this:
{
"_id": "fd87b66087503d760fa501fa49029f94",
"_rev": "1-e2be19d447c98d624c2c8492eaf0a3f4",
"type": "product",
"name": "Blanc de Morgex et de la Salle Brut Extreme 2014",
"category": "Wine",
"subcategory": null,
"zone": "Italy",
"nation": "Valle d'Aosta",
"province": "Morgex, AO",
"cellar": "Cave Mont Blanc",
"price": 30,
"structure": null,
"year": 2014,
"mescita": null,
"tag": null
}
The query I wrote should return the available years of products that match some filters. This is the query, with reduce : _count:
function (doc) {
if(doc.category && doc.type == 'product' && doc.year != null) {
emit(doc.year , 1);
}
}
If I try it with Postman adding the group = true parameter everything works and the result is something like:
{
"rows": [
{
"key": 2004,
"value": 2
},
{
"key": 2006,
"value": 2
},
{
"key": 2008,
"value": 2
}
]
}
The problem is when i run this view with Pouchdb with the following code which return a JSON with an empty array:
wine_db.query('wine_list/years', {reduce: '_count', key : "Bollicine", group : true, group_level: 2}).then(function(doc) {
years_list = doc;
console.log('getting year list');
console.log(doc);
}).catch(function(err){
console.log(err);
});
I've tried to play a little with the parameters of the function and even changing the function to return just a list of all the years, but nope.
I can't find the problem neither a different solution so I'm open to every suggestion you can have.
Another solution (group result)
Working on the indications and on the solution suggested by #user3405291 I finally found a way to group the results by year.
Since the emit function return a complex key ['CATEGORY', YEAR] I can use the startkey and endkey parameters to query the result just for a section of the index returned keeping this way the reduce function enable to group the result.
In the end the view function is:
function (doc) {
if(doc.category && doc.type == 'product' && doc.year) {
emit([doc.category, doc.year], doc.year );
}
}
And the Pouchdb query:
wine_db.query('wine_list/years',
{
startkey : ['CATEGORY'],
endkey : ['CATEGORY', {}],
group: true
}
).then(function (doc) {
years_list = doc;
console.log(years_list);
}).catch(function (err) {
console.log(err);
});
The result, where value is the total number of elements with that index:
{
"rows": [
{
"key": [
"Bollicine",
2004
],
"value": 2
},
{
"key": [
"Bollicine",
2006
],
"value": 2
},
{
"key": [
"Bollicine",
2008
],
"value": 2
}
]
}

Answer 1

In your view map function you emit the year as the key/index:
emit(doc.year , 1);
Now, I'm not sure why your are doing your query with a key like {key : "Bollicine"}:
wine_db.query('wine_list/years', {key : "Bollicine"})
.then(res=>{console.log(res)})
Of course you would get an empty response, because your view is actually indexing your docs according to year. I think you might want to do a query with a key like: {key : "2014"}
UPDATE
Based on your comments, I feel like you need to find docs based on both year and category. I'm not sure if I understand what you want, but this may help you: change your view map function like this:
function (doc) {
if(doc.category && doc.type == 'product' && doc.year) {
emit([doc.year, doc.category] , 1);
}
}
The above view will index your docs according to both year and category. You then query your view like this:
wine_db.query('wine_list/years', {key : ['2014', 'Bollicine']})
.then(res=>{console.log(res)})
The above query will give you all the docs with year field equal to 2014 and category field equal to Bollicine.
Second Update
your code works, but I just get the result for the year 2014. What I'm trying to accomplish is to get all the available years given a specific category
One solution is this:
function (doc) {
if(doc.category && doc.type == 'product' && doc.year) {
emit(doc.category, doc.year);
}
}
The above view will index your docs according to category as key and will return the year as value. Therefore you can query like this:
wine_db.query('wine_list/years', {key : 'Bollicine'})
.then(res=>{console.log(res)})
You should get a response like this, by which you have all the available years for Bollicine category:
{
"total_rows": 400,
"offset": 0,
"rows": [
{
"key": "Bollicine",
"value": "2014"
},
{
"key": "Bollicine",
"value": "2015"
},
{
"key": "Bollicine",
"value": "2018"
}
]
}