聚合：根据子文档中的字段返回文档

Question

I'm using an aggregation to return data via a lookup to build the links between documents.

At the moment, the linking is working when User A creates links between their own assets to navigate.

But if User A is viewing an asset that's been shared with them by User B and navigates to one that has a link to an asset that hasn't been shared with them, those are the documents I need to exclude from the results.

So, I need the documents for assets that have a document in attributes that contains my userId , or — as in the $match — the $_id of an attribute that's in the attributes array in assets . When an asset is shared with someone, a document in attributes is created.

The data for a Link is:

{
  "_id": {
    "$oid": "63769c377615fe4cdb4995a6"
  },
  "userId": "620920aa9ddac2074a50472f",
  "toAsset": {
    "$oid": "63769c117615fe4cdb499515"
  },
  "fromAsset": {
    "$oid": "63769c067615fe4cdb4994d9"
  },
  "comment": "<p>Linking of Note 0001 to Note 0002.</p>",
  "createdAt": {
    "$date": {
      "$numberLong": "1668717623761"
    }
  },
  "updatedAt": {
    "$date": {
      "$numberLong": "1668717623761"
    }
  },
  "isEmbedded": false,
  "isActive": true,
  "__v": 0
}

The data for an Asset, as in toAsset and fromAsset, is:

{
  "_id": {
    "$oid": "6377a8d834671794449f0dca"
  },
  "userId": "636b73f31527830f7bd7a47e",
  "folderId": "636b73f31527830f7bd7a482",
  "title": "Note that hasn't been shared",
  "note": "<p>Here's a Note that hasn't been shared.</p>",
  "typeOfAsset": "note",
  "createdAt": {
    "$date": {
      "$numberLong": "1668786392389"
    }
  },
  "updatedAt": {
    "$date": {
      "$numberLong": "1668786392389"
    }
  },
  "isActive": 3,
  "meta": [...],
  "preferences": [...],
  "sequence": 1,
  "tags": [],
  "attributes": [
    {
      "$oid": "6377a8d834671794449f0dc8"
    }
  ],
  "__v": 0
}

I'm using attributes to manage what assets have been shared with whom, and the data is:

{
  "_id": {
    "$oid": "6377a8d834671794449f0dc8"
  },
  "userId": "636b73f31527830f7bd7a47e",
  "numberOfViews": 2,
  "isFavourite": false,
  "isToRead": false,
  "typeOfAccess": "isOwner",
  "sharing": {
    "typeOfShare": "withUsers",
    "sharedWith": [],
    "segementsForUrl": []
  },
  "__v": 0
}

Now, the task here is to somehow how return the assets that have been shared, but after a bunch of different attempts (as per the code that's been commented out), I've so far failed.

The code is:

const match = {
  $match: {
    [args.directionOfLink]: new mongoose.Types.ObjectId(args.assetId)
  }
}

const project = {
  $project: {
    _id: 0,
    id: '$_id',
    userId: 1,
    [directionOfLink]: 1,
    comment: 1,
    createdAt: 1,
    updatedAt: 1,
    isActive: 1,
    score: {
      $meta: 'searchScore'
    }
  }
}

const lookup = {
  $lookup: {
    from: 'assets',
    localField: directionOfLink,
    foreignField: '_id',
    let: { attributesInAsset: '$attributes' },
    pipeline: [
      {
        $lookup: {
          from: 'attributes',
          as: 'attributes',
          pipeline: [{
            $match: {
              $expr: {
                $in: [ '$_id', '$$attributesInAsset' ]
                // $and: [
                  // { $eq: [ '$userId', context.body.variables.userId ] },
                  // { $in: [ '$typeOfAccess', ['isOwner', 'asAuthor', 'asReader'] ] },
                // ]
              }
            }
          }]
        }
      },
      {
        $project: {
          _id: 1,
          userId: 1,
          folderId: 1,
          title: 1,
          typeOfAsset: 1,
          attributes: 1,
          createdAt: 1,
          updatedAt: 1,
          isActive: 1
        }
      }
    ],
    as: directionOfLink
  }
}

Here, directionOfLink is either "toAsset" or "fromAsset".

Any thoughts would be appreciated.

Answer 1

As a non expert in MongoDB, it's possible this isn't the most performant approach, but at least it works:

const lookup = {
  $lookup: {
    from: 'assets',
    localField: directionOfLink,
    foreignField: '_id',
    as: directionOfLink,
    pipeline: [
      {
        $lookup: {
          from: 'assets_attributes',
          as: 'attributesInAssets',
          pipeline: [
            {
              $match: {
                $expr: {
                  $and: [
                    { $eq: [ '$userId', context.body.variables.userId ] },
                    { $in: [ '$typeOfAccess', ['isOwner', 'asAuthor', 'asReader'] ] },
                  ]
                }
              }
            }
          ]
        }
      },
      {
        $unwind: '$attributesInAssets'
      },
      {
        $match: {
          $expr: {
            $in: [ '$attributesInAssets._id', '$attributes' ]
          }
        }
      },
      {
        $group: {
          _id: '$_id',
          userId: { $first: '$userId' },
          folderId: { $first: '$folderId' },
          title: { $first: '$title' },
          typeOfAsset: { $first: '$typeOfAsset' },
          createdAt: { $first: '$createdAt' },
          updatedAt: { $first: '$updatedAt' },
          isActive: { $first: '$isActive' },
          attributes: { $first: '$attributes' },
          attributesInAssets: {
            $push: '$attributesInAssets._id'
          }
        }
      },
      {
        $project: {
          _id: 1,
          userId: 1,
          folderId: 1,
          title: 1,
          typeOfAsset: 1,
          attributes: 1,
          attributesInAssets: 1,
          createdAt: 1,
          updatedAt: 1,
          isActive: 1
        }
      }
    ]
  }
}

const redact = {
  $redact: {
    $cond: {
      if: {
        $gt: [ {
          $size: `$${directionOfLink}`
        }, 0 ]
      },
      then: '$$KEEP',
      else: '$$PRUNE'
    }
  }
}