通过多个字段值获取文档

Question

I have an food mongodb schema as follows:

{
name: 'Pork meat',
category: 'Meat'
}

Exists several categories and many items which belong to a specific category.

I want to sort items by category like this:

{
category: 'Meat', items: [ITEMS_WHICH_BELONG_TO_THIS_CATEGORY]
},
{
category: 'Drink', items: [ITEMS_WHICH_BELONG_TO_THIS_CATEGORY]
},
{
category: 'Souce', items: [ITEMS_WHICH_BELONG_TO_THIS_CATEGORY]
}

I have this code:

const categories = await Food.find().distinct('category').exec()
const result = []
    for (let i = 0; i < categories.length; i++) {
      result.push({ category: categories[i], items: await Food.find({ category: categories[i] }).exec() })
    }

This is good, but can I optimize this code? Can I do this in one query?

Answer 1

You can optimize your loop by using map or forEach to do this

const result = categories.map((category) => {
   return {
    category,
    items: await Food.find({ category: category }).exec()
}
})

Answer 2

Use Aggregation pipeline for grouping your Food items based on Categories :

Food.aggregate([{
    $group : {
        _id : "$category",
        items : { $push : "$name"}
    }
}],function(err, result){
    //result will have food items grouped by category
})

See MongoDB Aggregation and $group for more information.