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Merge pull request #44 from mongodb-developer/improve-arrays
Improve arrays
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‎babel.config.js

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This file was deleted.

‎docs/1-mongodb-atlas/setup-lab.mdx

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@@ -6,6 +6,8 @@ description: Setting up your MongoDB Atlas account, importing Library data
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To follow along, you'll need:
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- A MongoDB Atlas account.
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- Test data. In this case, this is book, author, and review data for a library management system.
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- Test data. In this case, this is `book`, `author`, and `review` data for a library management system.
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👐 To get both, open the [intro lab](https://mongodb-developer.github.io/intro-lab/docs/intro) and follow it (only takes 10-15 mins) to get your database ready. Return here when finished!
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👐 To get this data set, open the [intro lab](https://mongodb-developer.github.io/intro-lab/docs/intro) and follow it (do only sections `MongoDB Atlas` and `Importing Data`, this should take you 10-15 mins) to get your database ready.
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Return here when finished!

‎docs/20-what-is-aggregation/2-sql-vs-aggregation.mdx

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We read this from the inside. If there's too much nesting, it's not easy to follow.
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### Get authors’ bios with books that have an average 5-star rating
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```SQL
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SELECT authors.name, authors.bio
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FROM library.authors authors
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JOIN library.author_book author_book_join ON authors.id = author_book_join.author_id
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JOIN (
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SELECT books.id
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FROM library.books books
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JOIN library.reviews reviews ON books.id = reviews.book_id
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GROUP BY books.id
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HAVING AVG(reviews.rating) = 5
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) five_star_books ON author_book_join.book_id = five_star_books.id;
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```
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### Get annual, average and max spending from customers in all cities
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```SQL
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SELECT
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city,
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## Equivalent MongoDB aggregation pipeline
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### Get authors’ bios with books that have an average 5-star rating
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We o through 4 stages:
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- group all the reviews for every book, calculating the average rating.
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- filter out all average ratings other than 5.
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- now we have reviews with 5 stars, but we also want the author bio, so we join with author to get the bio.
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- we add a new field called `bio` with just the author's bio.
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```js
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db.reviews.aggregate([
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{
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$group: {
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_id: "$bookId",
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averageRating: {
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$avg: "$rating",
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},
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},
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},
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{ $match: { averageRating: 5 } },
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{ $lookup: {
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from: "authors",
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localField: "_id",
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foreignField: "books",
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as: "author",
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},
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},
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{$addFields: {
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bio: "$author.bio"
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}},
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])
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```
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### Get annual, average and max spending from customers in all cities
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Here we pass three stages: one to return one document per element in the `address` array, and then we filter out to get only the documents that have a `home` address location. Finally, we do the grouping. As we'll see, this can be split and tested separately and resembles our code.
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```js

‎docs/20-what-is-aggregation/3-structure-aggregation.mdx

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## Example
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An aggregation pipeline that does the same as the above SQL statement could be:
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```
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db.mycollection.aggregate([
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{
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$sort:
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/**
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* Provide any number of field/order pairs.
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*/
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{
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num_mflix_comments: -1,
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},
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},
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{
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$limit:
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/**
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* Provide the number of documents to limit.
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*/
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1,
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},
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{
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$unwind:
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/**
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* path: Path to the array field.
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* includeArrayIndex: Optional name for index.
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* preserveNullAndEmptyArrays: Optional
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* toggle to unwind null and empty values.
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*/
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{
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path: "$cast",
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// Inside the current database, in the collection named reviews
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db.reviews.aggregate([
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{
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// group all reviews for the same book
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$group: {
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_id: "$bookId",
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averageRating: {
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$avg: "$rating",
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},
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},
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},
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{
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$project:
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/**
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* Specifications: The fields to
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* include or exclude.
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*/
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{
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cast: 1,
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// filter out all reviews that have an average other than 5
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{ $match: { averageRating: 5 } },
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// JOIN with author collection to get all the author info
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{ $lookup: {
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from: "authors",
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localField: "_id",
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foreignField: "books",
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as: "author",
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},
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},
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// add a field called bio
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{$addFields: {
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bio: "$author.bio"
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}},
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])
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```

‎docs/40-using-arrays/10-types-of-arrays.mdx

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import Tabs from '@theme/Tabs';
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import TabItem from '@theme/TabItem';
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# 👐 Types of arrays
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A JSON array can contain __simple values__ (scalar values) or __objects__. In our data, `books` have a scalar array of the `genres` this book belongs to. It also has several arrays of objects, like the `authors` of a book, `attributes` and `reviews`.
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Let's get one book:
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<Tabs groupId="aggregations">
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<TabItem value="atlas" label="Atlas UI">
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Remember to select the `books` collection in the UI.
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```js
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[
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{ $limit: 1 }
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]
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```
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</TabItem>
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<TabItem value="mongodb-shell" label="MongoDB Shell">
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```js
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db.books.aggregate([
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{ $limit: 1 }
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])
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```
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</TabItem>
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</Tabs>
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👐 Run this aggregation to get one book.
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I got this one. (It can change depending on the data source you imported.)
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```js
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[
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{
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"_id": "0002005018",
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"title": "Clara Callan: A novel",
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"authors": [
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{
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"_id": "64cc2db4830ba29148da4c3b",
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"name": "Richard Bruce Wright"
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}
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],
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"genres": [
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"Women Teachers",
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"Young Women",
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"Actresses",
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"Sisters"
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],
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"pages": 414,
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"year": 2001,
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"synopsis": "Giller Prize Winner 2001. Richard B. Wright. A Phyllis Bruce Book.",
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"cover": "https://images.isbndb.com/covers/50/12/9780002005012.jpg",
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"attributes": [
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{
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"key": "edition",
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"value": "1st"
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},
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{
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"key": "dimensions",
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"value": "Height: 11.11 Inches, Length: 6.11 Inches, Weight: 1 Pounds, Width: 1.11 Inches"
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},
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{
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"key": "isbn13",
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"value": "9780002005012"
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},
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{
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"key": "msrp",
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"value": "0.00"
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},
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{
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"key": "isbn",
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"value": "0002005018"
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},
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{
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"key": "isbn10",
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"value": "0002005018"
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}
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],
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"totalInventory": 2,
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"available": 2,
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"binding": "Hardcover",
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"language": "en",
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"publisher": "HarperFlamingoCanada",
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"longTitle": "Clara Callan: A novel",
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"reviews": [
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{
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"_id": {
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"$oid": "6526bbc2e4e804888dfedf37"
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},
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"text": "yd",
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"name": "Holy Dingo",
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"rating": 1,
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"timestamp": 1697037250625
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},
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{
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"_id": {
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"$oid": "651c0f4b24193d51c4c734a3"
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},
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"text": "Great!",
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"name": "Brash Platypus",
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"rating": 5,
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"timestamp": 1696337739128
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}
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]
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}
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]
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```
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### Array of strings example
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```json
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"genres": [
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"Women Teachers",
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"Young Women",
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"Actresses",
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"Sisters"
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],
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```
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### Array of objects example
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```json
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"attributes": [
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{
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"key": "edition",
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"value": "1st"
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},
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{
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"key": "dimensions",
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"value": "Height: 11.11 Inches, Length: 6.11 Inches, Weight: 1 Pounds, Width: 1.11 Inches"
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},
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{
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"key": "isbn13",
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"value": "9780002005012"
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},
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{
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"key": "msrp",
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"value": "0.00"
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},
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{
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"key": "isbn",
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"value": "0002005018"
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},
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{
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"key": "isbn10",
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"value": "0002005018"
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}
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],
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```

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