Rethinkdb: Calculate tag occurrence per user - rethinkdb

Question

My table contains documents that look like this:
[{ user: {
key: '100'
},
product: {
name: 'Product 1',
tags: [ 'tag1', 'tag2' ],
}
}, { user: {
key: '100'
},
product: {
name: 'Product 1',
tags: [ 'tag1', 'tag3' ],
}
}, ...]
I would like to create a query which would
groupe documents by the user.key field (1 document per user on result),
the product.tags would be an object (instead of array) with tag occurrences count for each tag.
Result example:
[ { user: {
key: '100'
},
product: {
name: 'Product 1',
tags: {
tag1: 2, // tag1 found 2x for user.key=100
tag2: 1, // tag2 found 1x for user.key=100
tag3: 1
}
}
}, ...]
I think I could do this by mapping and reducing but I have problems - I'm using rethinkdb for the first time.

Answer 1

Here's a way to do it:
// Group by user key
r.table('30400911').group(r.row('user')('key'))
// Only get the product info inside the reduction
.map(r.row('product'))
.ungroup()
.map(function (row) {
return {
user: row('group'),
// Group by name
products: row('reduction').group('name').ungroup().map(function (row) {
return {
name: row('group'),
// Convert array of tags into key value pairs
tags: r.object(r.args(row('reduction').concatMap(function (row) {
return row('tags')
}).group(function (row) {
return row;
}).count().ungroup().concatMap(function (row) {
return [row('group'), row('reduction')]
})))
}
})
}
})
For the following data:
{
"id": "0565e91a-01ca-4ba3-b4d5-1043c918c79d" ,
"product": {
"name": "Product 2" ,
"tags": [
"tag1" ,
"tag3"
]
} ,
"user": {
"key": "100"
}
} {
"id": "39999c9f-bbef-4cb7-9311-2516ca8f9ba1" ,
"product": {
"name": "Product 1" ,
"tags": [
"tag1" ,
"tag3"
]
} ,
"user": {
"key": "100"
}
} {
"id": "566f3b79-01bf-4c29-8a9c-fd472431eeb6" ,
"product": {
"name": "Product 1" ,
"tags": [
"tag1" ,
"tag2"
]
} ,
"user": {
"key": "100"
}
} {
"id": "8e95c467-cedc-4734-ad4d-a1f7a371efd5" ,
"product": {
"name": "Product 1" ,
"tags": [
"tag1" ,
"tag2"
]
} ,
"user": {
"key": "200"
}
}
The results would be:
[
{
"products": [
{
"name": "Product 1" ,
"tags": {
"tag1": 2 ,
"tag2": 1 ,
"tag3": 1
}
}, {
"name": "Product 2" ,
"tags": {
"tag1": 1 ,
"tag3": 1
}
}
],
"user": "100"
} ,
{
"products": [
{
"name": "Product 1" ,
"tags": {
"tag1": 1 ,
"tag2": 1
}
}
] ,
"user": "200"
}
]