Sequelize count returns wrong count when association models included

Sequelize count returns wrong count when association models included, in my case, via the model’s defaultScope.

What are you doing?

I have a Post model. The Post model has attachments (oneToMany)

I’m trying to count posts [with attachments] using Sequelize’s count

// Post model
module.exports = (sequelize, DataTypes) => {
  const Post = sequelize.define(
    'Post',
    {
      id: {
        primaryKey: true,
        type: DataTypes.UUID
      },
      title: DataTypes.STRING
    }
  )

  Post.associate = models => {
    Post.hasMany(models.PostAttachment, { as: 'attachments' })

    Post.addScope('defaultScope', {
      include: [
        { model: models.PostAttachment, as: 'attachments' }
      ],
      order: [
        ['id', 'ASC']
      ]
    }, {
     override: true
    })
  }

  return Post
}

// PostAttachment model
module.exports = (sequelize, DataTypes) => {
  const PostAttachment = sequelize.define(
    'PostAttachment',
    {
      id: {
        primaryKey: true,
        type: DataTypes.UUID
      },
      key: DataTypes.STRING
    }
  )

  PostAttachment.associate = models => {
    PostAttachment.belongsTo(models.Post)
  }

  return PostAttachment
}

Sequelize query

const posts = await Post.findAll()
const total = await Post.count()

return { posts, total }

Scenario 1: Single Post, multiple PostAttachments

Posts table

id	title	createdAt	updatedAt
f8d68fc0-48b1-4e90-af73-c9a4dc577461	Title1	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00

PostAttachments table

id	key	PostId	createdAt	updatedAt
410819f6-d1c4-44f4-9a52-edbac765e714	Key1	f8d68fc0-48b1-4e90-af73-c9a4dc577461	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00
754ca095-4967-4472-a0f4-1a8e2d761a24	Key2	f8d68fc0-48b1-4e90-af73-c9a4dc577461	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00
754ca095-4967-4472-a0f4-1a8e2d761a25	Key3	f8d68fc0-48b1-4e90-af73-c9a4dc577461	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00

What do you expect to happen?

I’m expecting to get 1 post and total sum 1:

{
  "posts": [{...}],
  "total": 1
}

What is actually happening?

I’m actually getting 1 post and total sum 3:

{
  "posts": [{...}],
  "total": 3
}

Scenario 2: Multiple Posts, multiple PostAttachments

Posts table

id	title	createdAt	updatedAt
f8d68fc0-48b1-4e90-af73-c9a4dc577461	Title1	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00
01a528d2-8696-465f-8739-2b32bc52ceca	Title2	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00
01a528d2-8696-465f-8739-2b32bc52cecb	Title3	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00

PostAttachments table

id	key	PostId	createdAt	updatedAt
410819f6-d1c4-44f4-9a52-edbac765e714	Key1	f8d68fc0-48b1-4e90-af73-c9a4dc577461	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00
754ca095-4967-4472-a0f4-1a8e2d761a24	Key2	f8d68fc0-48b1-4e90-af73-c9a4dc577461	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00
754ca095-4967-4472-a0f4-1a8e2d761a25	Key3	f8d68fc0-48b1-4e90-af73-c9a4dc577461	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00
754ca095-4967-4472-a0f4-1a8e2d761a26	Key4	01a528d2-8696-465f-8739-2b32bc52ceca	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00
754ca095-4967-4472-a0f4-1a8e2d761a27	Key5	01a528d2-8696-465f-8739-2b32bc52ceca	2018-05-23 16:47:09.228000 +00:00	2018-05-23 16:47:09.228000 +00:00

What do you expect to happen?

I’m expecting to get 3 posts and total sum 3:

{
  "posts": [{...}, {...}, {...}],
  "total": 3
}

What is actually happening?

I’m actually getting 3 posts and total sum 6:

{
  "posts": [{...}, {...}, {...}],
  "total": 6
}

I ran a few configurations through. It appears the count calculations are based on each post multiplied by the maximum between 1 and the number of attachments per post, so:

• PostA * Math.max(1, 3 attachments) = 3
• PostB * Math.max(1, 2 attachments) = 2
• PostC * Math.max(1, 0 attachments) = 1

---

Dialect: postgres Dialect version: XXX Database version: 11.1 Sequelize version: 4.43.0 Tested with latest release: No (If yes, specify that version)

Related: #1517, #9481, #9669, #10239

[dsmackie]

My solution, which may break other queries but works for my application, is to add a distinct condition. The distinct param is only applied to the count query so it ensures that the correct document count is returned, whilst allowing the internal Sequelize aggregation of associations to continue as intended.

Adding distinct: 'Article.id' to my Article.findAndCountAll query gives me the correct article count.

[JamesMGreene]

Here’s an enhanced workaround that may not cover every case but hasn’t failed me so far:

// Add a permanent global hook to prevent unknowingly hitting this Sequelize bug:
//   https://github.com/sequelize/sequelize/issues/10557
sequelize.addHook('beforeCount', function (options) {
  if (this._scope.include && this._scope.include.length > 0) {
    options.distinct = true
    options.col = this._scope.col || options.col || `"${this.options.name.singular}".id`
  }

  if (options.include && options.include.length > 0) {
    options.include = null
  }
})

HTH others. 💝