topic Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock in Application Development and Automation Discussions

SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

qmacro — Fri, 11 Aug 2023 14:50:40 GMT

(Check out the SAP Developer Challenge - APIs blog post for everything you need to know about the challenge to which this task relates!)

In this task you'll move from the public Northwind service to a simple version powered by CAP, and explore data with an OData operation and some system query options.

Background

The OASIS curated Northwind service is great, but it's also sometimes useful to have one's own version. There's an extremely simplified version of the classic Northwind service, called Northbreeze (get it?) at https://developer-challenge.cfapps.eu10.hana.ondemand.com/odata/v4/northbreeze.

This Northbreeze service is powered by the SAP Cloud Application Programming Model (CAP) and offers four entity sets:

Products
Suppliers
Categories
Summary of sales by years

(Well there's technically a fifth, TotalProducts, but that's just a calculation projection on the count of products).

The reason for running our own version of Northwind is that we can modify and extend it as we see fit, plus being based on CAP, we can learn about and experiment with CAP's rich support for serving OData APIs.

In this task you'll start to become familiar with the data offered.

Specifically for this task, you'll need to become familiar with the Products data. To do that, have a look at the Northbreeze service's metadata document at https://developer-challenge.cfapps.eu10.hana.ondemand.com/odata/v4/northbreeze/$metadata.

Identify the EntityContainer element that describes the entity sets available, in the form of EntitySet elements, and find the element describing the entity set with the name Products, which should look like this:

<EntitySet Name="Products" EntityType="Northbreeze.Products">
 <NavigationPropertyBinding Path="Category" Target="Categories"/>
 <NavigationPropertyBinding Path="Supplier" Target="Suppliers"/>
</EntitySet>

You can see that this entity set is a collection of Northbreeze.Products entity types. The 'Northbreeze' part is essentially the namespace, generated based on the service name. Follow the trail to the Products entity type, which will be an element outside the EntityContainer element, but still within the Northbreeze-namespaced Schema element.

The Products entity type should look like this:

<EntityType Name="Products">
 <Key>
 <PropertyRef Name="ProductID"/>
 </Key>
 <Property Name="ProductID" Type="Edm.Int32" Nullable="false"/>
 <Property Name="ProductName" Type="Edm.String"/>
 <Property Name="QuantityPerUnit" Type="Edm.String"/>
 <Property Name="UnitPrice" Type="Edm.Decimal" Scale="variable"/>
 <NavigationProperty Name="Category" Type="Northbreeze.Categories" Partner="Products">
 <ReferentialConstraint Property="Category_CategoryID" ReferencedProperty="CategoryID"/>
 </NavigationProperty>
 <Property Name="Category_CategoryID" Type="Edm.Int32"/>
 <NavigationProperty Name="Supplier" Type="Northbreeze.Suppliers" Partner="Products">
 <ReferentialConstraint Property="Supplier_SupplierID" ReferencedProperty="SupplierID"/>
 </NavigationProperty>
 <Property Name="Supplier_SupplierID" Type="Edm.Int32"/>
 <Property Name="UnitsInStock" Type="Edm.Int32"/>
 <Property Name="UnitsOnOrder" Type="Edm.Int32"/>
 <Property Name="ReorderLevel" Type="Edm.Int32"/>
 <Property Name="Discontinued" Type="Edm.Boolean"/>
</EntityType>

Amongst other things, you can see that a product has an ID (ProductID), a name (ProductName), a count of the number of units currently in stock (UnitsInStock) and a boolean that is used to indicate whether or not a product is discontinued (Discontinued).

Request the first few products to see data for these and the other properties, via https://developer-challenge.cfapps.eu10.hana.ondemand.com/odata/v4/northbreeze/Products?$top=5. You should see something like this:

{
 "@odata.context": "$metadata#Products",
 "value": [
 {
 "ProductID": 1,
 "ProductName": "Chai",
 "QuantityPerUnit": "10 boxes x 20 bags",
 "UnitPrice": 18,
 "Category_CategoryID": 1,
 "Supplier_SupplierID": 1,
 "UnitsInStock": 39,
 "UnitsOnOrder": 0,
 "ReorderLevel": 10,
 "Discontinued": false
 },
 {
 "ProductID": 2,
 "ProductName": "Chang",
 "QuantityPerUnit": "24 - 12 oz bottles",
 "UnitPrice": 19,
 "Category_CategoryID": 1,
 "Supplier_SupplierID": 1,
 "UnitsInStock": 17,
 "UnitsOnOrder": 40,
 "ReorderLevel": 25,
 "Discontinued": false
 },
 {
 "ProductID": 3,
 "ProductName": "Aniseed Syrup",
 "QuantityPerUnit": "12 - 550 ml bottles",
 "UnitPrice": 10,
 "Category_CategoryID": 2,
 "Supplier_SupplierID": 1,
 "UnitsInStock": 13,
 "UnitsOnOrder": 70,
 "ReorderLevel": 25,
 "Discontinued": false
 },
 {
 "ProductID": 4,
 "ProductName": "Chef Anton's Cajun Seasoning",
 "QuantityPerUnit": "48 - 6 oz jars",
 "UnitPrice": 22,
 "Category_CategoryID": 2,
 "Supplier_SupplierID": 2,
 "UnitsInStock": 53,
 "UnitsOnOrder": 0,
 "ReorderLevel": 0,
 "Discontinued": false
 },
 {
 "ProductID": 5,
 "ProductName": "Chef Anton's Gumbo Mix",
 "QuantityPerUnit": "36 boxes",
 "UnitPrice": 21.35,
 "Category_CategoryID": 2,
 "Supplier_SupplierID": 2,
 "UnitsInStock": 0,
 "UnitsOnOrder": 0,
 "ReorderLevel": 0,
 "Discontinued": true
 }
 ]
}

Your task

Your task is to calculate the total stock quantity (i.e. the total units in stock) for all current products, i.e. products that are not been marked as discontinued. The result of this calculation should be a number.

Once you have calculated the number, which should be an integer, you should hash it and post the hash as a new reply to this discussion thread, as described in Task 0 - Learn to share your task results and in a similar way to how you've done this in the previous task.

Hints and tips

Like all tasks in this challenge, you are free to approach this one however you see fit. One way would be to request all the products (https://developer-challenge.cfapps.eu10.hana.ondemand.com/odata/v4/northbreeze/Products) and manually sum the values of the relevant UnitsInStock properties.

But where's the fun in that?

How about requesting the entire products entity set in your favorite language and obtaining result by parsing the response and using that language to make the calculation?

You could also use OData's $filter system query option to first reduce the entity set result to only those products that have the value false for the Discontinued property.

And what about the $count facility, which in OData V4 is now a system query option as well something you can append to a resource path?

This would also be a good opportunity to take your first steps exploring some great new OData V4 features supported by CAP, such as data aggregation.

For discussion

How did you approach this task? If you used a programming language, which one did you use, and how did you do it? If you used an $apply based data aggregation feature, what was it, and was was your experience using it?

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

vladimirs_semikins — Mon, 07 Aug 2023 06:32:17 GMT

3074a722566a0d38b50a5f3f5c2804ed4fa37dcc94f8f33ed2586a9f6c56f3ab

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

vladimirs_semikins — Mon, 07 Aug 2023 06:34:11 GMT

I was today years old when I found out that OData v4 supports data aggregation 🫣

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

ajmaradiaga — Mon, 07 Aug 2023 11:26:26 GMT

7e30e0c2f9e6214f7dcda4c45056ee7b1755f4a0c3efa73f0b568d93147e6123

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

UweFetzer_se38 — Mon, 07 Aug 2023 07:47:48 GMT

76a789b93f7545767ddf4b44cd4a37a7e2b976140a10c1e4c262568daf527d99

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

UweFetzer_se38 — Mon, 07 Aug 2023 07:48:57 GMT

The hashed "value" should only be the number, right?

I've used "apply" with filter and aggregate.

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

ceedee666 — Mon, 07 Aug 2023 07:51:55 GMT

cfa7b85bac1866665ea24e08e8bf20472ceae1b42d1dcca8778597789bd04be0

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

ceedee666 — Mon, 07 Aug 2023 07:55:02 GMT

I solved this task using three approaches:

Getting all data form the service and perform the filtering and aggregation in Python 🐍
Filtering the data using OData '$filter` and the aggregation in Python 🐍
Using OData data for filtering and aggregation as described

Thanks @qmacro for providing the nice hints!

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

FooThePolarBear — Mon, 07 Aug 2023 08:02:02 GMT

94d74a329419222662e42356a0ba4c5c07ceaf9b550c53cabc0fa45847d39080

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

SandipAgarwalla — Mon, 07 Aug 2023 08:19:55 GMT

6141c65b9ea179fcb34c1ba2505fd19badcbf79d77b1cd789632045fc0ca35aa

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

nicoschoenteich — Mon, 07 Aug 2023 08:20:24 GMT

d8342a9512672b9987909600065c0da57f64a77f93f400259e04afd1d31e565f

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

nicoschoenteich — Mon, 07 Aug 2023 08:20:58 GMT

Same!

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

SandipAgarwalla — Mon, 07 Aug 2023 08:22:45 GMT

I used couple of ways to get the total number

1) wrote a small nodejs program, to get all the products and then using the filter and sum approach

2) used $apply to filter and aggregate. Took a while to get the correct syntax. But $apply & aggregate is so powerful, it was a great learning.

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

harsh_itaverma — Mon, 07 Aug 2023 08:31:31 GMT

30271d0c9c3a30e06cb955411e56c388e591ce1fa9606758a269cf97fa7c9cb4

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

harsh_itaverma — Mon, 07 Aug 2023 08:49:27 GMT

Used data aggregation to get the total Unit in stocks; with $apply query option, first used a filter transformation to get Current Products and then used aggregate transformation with sum method to return the total value.

Being a JavaScript developer, just to make sure I was right; I did parse the response and used array traversing to get the total too! But the data aggregation approach was much easier and cleaner.

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

qmacro — Mon, 07 Aug 2023 08:55:23 GMT

Thanks for asking, @UweFetzer_se38 - the text in the "Your task" was a bit vague. I've modified it, thanks! And yes, it's just the number (total stock) that should be sent to be hashed 👍

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

qmacro — Mon, 07 Aug 2023 08:59:40 GMT

And lots more! Here are some interesting filter examples too https://github.com/SAP-samples/odata-basics-handsonsapdev/blob/main/filter.md cc @nicoschoenteich @ceedee666 @SandipAgarwalla @harsh_itaverma et al.

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

qmacro — Mon, 07 Aug 2023 09:00:33 GMT

It's great to have so many possibilities. Thanks for sharing, and thanks for doing this task in multiple ways 💪

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

qmacro — Mon, 07 Aug 2023 09:03:36 GMT

Nice once @SandipAgarwalla . In your JS program, what did you use? For example: in mine, I used filter and reduce, of course, as I'm a fan of the functional style of programming. I find reduce a particularly powerful and beautiful function.

I've written a few posts on my blog about reduce. Here's one: ES6, reduce and pipe.

Re: SAP Developer Challenge - APIs - Task 2 - Calculate Northbreeze product stock

qmacro — Mon, 07 Aug 2023 09:04:23 GMT

Great work @harsh_itaverma ! Feel free also to share more detail of what you did. I love learning from other folks' approaches.