Shulou(Shulou.com)06/01 Report--

Unique url slug: this field is usually the unique index to speed up the query and ensure uniqueness. It provides a meaningful url structure, which is beneficial to seo. Usually the url of https://xxxx.com/products/5d0332be5d530000c4002a03 is meaningless, like https://xxxx.com/products/wheelbarrow-9092.

So you can create a unique index on it:

To query all the columns in the catalog, you can use the $in operator:

Db.categories.find ({"_ id": {"$in": product ("category_ids")}})

Db.orders.find ({user_id: user ["user_id"]})

Users who query a specific order:

Db.users.findOne ({"_ id": order ["user_id"]})

There can be multiple reviews for each product, and an one-to-many relationship can be achieved by storing product_id in comments.

Why store username? In the case of sql, username is used to associate the users table. However, mongodb does not support join, and we can use two methods: query based on each comment in the user collection or accept the de-paradigm. However, queries based on each evaluation are not necessary, which adds unnecessary costs, especially if the username is frequently modified. So here we choose to optimize the query instead of formatting it.

It is worth mentioning that users can choose to support a certain evaluation, where the id of the comment user is saved in each evaluation, which can organize the user to vote multiple times, and can help us query all the users who voted.

All votes are cached to helpful_votes, which allows us to sort helpful comments based on votes. Caching is useful because mongodb does not allow us to query the size of the array in the document.

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