Backend Aggregate Pipeline

[gdcho]

Mongodb documentation

$sample - randomly selects "n" of documents from the database

{ $sample: { size: <positive integer N> } }

$lookup - performs an equality match on the localField to the foreignField from the documents of the from collection
$lookup syntax

{
   $lookup:
     {
       from: <collection to join>,
       localField: <field from the input documents>,
       foreignField: <field from the documents of the "from" collection>,
       as: <output array field>
     }
}

[gdcho]

API route handler

const getMainThread = req.query.random
        ? getRandomMainThreads(parseInt(req.query.count) || 6)
        : getMainThreads();

If req query key is random (True), getRandomMainThreads, else (False), getMainTreads
When getRandomMainThreads, if query count is not given, default is 6

[gdcho]

Postman GET URL: http://localhost:3000/api/threads/mainThread?random=True

{
"error": "Error: Could not find rootField queryRaw for action queryRaw for model undefined on rootType mutation"
}

[gdcho]

Actually Prisma does not support the aggregation pipeline syntax directly.
We have to use Prisma's query builder.

Prisma query builder documentation - using cursor pagination

Key points:

• take: limits the return count
• cursor: the starting point of the query

[gdcho]

{
    "error": "Error: \nInvalid `prisma.mainThread.findMany()` invocation:\n\n{\n  take: 6,\n  orderBy: [\n    {\n      id: 'asc'\n    }\n  ],\n  cursor: {\n    id: 0\n        ~\n  },\n  include: {\n    branchThread: true\n  }\n}\n\nArgument id: Got invalid value 0 on prisma.findManyMainThread. Provided Int, expected String.\n\n"
}

Get all the mainThread ids first

const entireIds = await prisma.mainThread.findMany({
      select: {
        id: true,
      },
    });