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Beautiful.

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And once we have set our database back to one product.

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Now let's see how we can set up aggregation pipeline and in the process, get average rating as well

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as count for all reviews for that one specific product.

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There will be two videos on this.

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First, I'll show you the gooey option and atlas.

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So essentially how we can do that in graphical interface.

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Therefore, if you're not logged in, please do so.

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And second will repeat the most steps in the code since we also want to interact with our product model

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because remember, both of those properties are actually on a product model.

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We'll just use reviews model to calculate that.

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So every time we update the reviews, we'll send off some code to a product.

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Now, when it comes to aggregation, it's pretty complex MongoDB topic.

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So if you want to find more info on some operators that I'm going to showcase, or if you want to find

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out about different setups, please utilize MongoDB docs since in that you can find all the information.

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So something that you are looking at the same database, the e-commerce one, you can see that one product.

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I have two reviews and I have three users now in order to set up aggregation.

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I just need to look for my collection, which in my case again, is going to be reviews and then we'll

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communicate with a product line.

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We bravely click here on the aggregation.

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And when it comes to aggregation pipeline, you need to think of it as steps so we can match all the

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product of animal group based on some kind of pattern.

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And then optionally, we can sort as well.

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Now, in our case, we're not going to add sorting.

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We're just looking for two things I want to match all the products where the product data is this one,

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which of course at the moment seems silly because that's the only reviews that I have for that one product.

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But we need to understand that eventually there's going to be more product and once I match all their

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views that one specific product I to run.

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What do I want to do?

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Well, I want a group, I want to group them and then take a look at the average rating, as well as

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how many reviews I have.

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So the first step is following where we go here.

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I want to look for Match.

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So that's the operating name again, if you want to find out more about the operator.

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Please utilize MongoDB docs.

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We go here with Match.

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And this is where I need to say Hey.

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I want to get all their views on where the property matters, something now, what is the property that

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I'm looking for?

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Well, it is product, correct?

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Why?

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Well, because if I take a look at my code, I can clearly see, but I'm going to be passing in the

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product I.D. so we can already put two and two together.

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Where since this is dynamic, since I'm getting here, this product that I want to match all the reviews

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where the product eddy is the same value.

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Correct.

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So let's go back here and the name here needs to match exactly because on my scheme, I have the product.

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So here we go with product.

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And yes, in this case, we'll hard code because we're working in a good way.

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But remember, in our code, it's going to be a little bit different.

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So now what I want to do is go with object I.D. and then just grab this sucker over here, make sure

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that you get the product one and also make sure that the syntax is correct.

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If you don't see any reviews, for example, if I remove this one, I won't see any reviews.

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That means that there's some kind of bug.

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So make sure that you also see two documents.

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And again, eventually this is going to be dynamic and eventually we'll have more of used for time being.

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All I'm saying is get me all the reviews where product key as this value.

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All right.

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That's the first step.

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So now we matched all documents in the next stage.

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Now we want to group them together.

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So we go with add stage and we're looking for group.

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And notice how right away they spin back some very useful examples.

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And keep in mind that this is something that we are constructing.

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Meaning in here, I'll create an I.D. property, and I want to set it equal to some kind of expression.

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Now to tell you, honestly, since we have both interviews for same product and our data is not that

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complex, we can actually pass here.

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No, this is the case where Mongol dogs really come in handy, where you can take a look, right?

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So group by expression.

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Now, in our case, we don't want a group based on anything.

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We really have the list and we're pretty much good to go.

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There's really no need for us to add anything expression.

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Now can you add here product I.D.?

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Yes, of course you can, if you want.

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But again, it's not going to make any kind of difference.

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The difference here is going to be if you have some kind of more specific data, but you want to go

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by.

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So again, imagine I don't know a reviews and you want to group by the a review rating.

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So that's the case where not only you're getting the list price, you want to group them by the rating.

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Hopefully, that's clear.

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And if not, then please utilize the box and you'll see that again.

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In this case, we have two options either I can just pass on your null since I'm looking for the entire

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list to begin with, or if you want to be really specific and you can type out the product here, but

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it's not going to make much of a difference.

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So next, we want to create some fields, correct, and we're looking for two things.

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We're looking for the average rating.

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And I also want to get the number of reviews.

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So first, if I just remove this field name and as a side note, again, this is something that we are

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creating.

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So I'm saying that there's going to be an I.D. property there now for the time being, the value will

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be now.

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And there's also going to be some other fields.

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So if I remove this moment, this is the only thing that I get back.

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Now what I also want is to get average rating, and that will be equal to.

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So this index is following where we need to set up here to curlies and then we're looking for another

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operator.

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And in this case, I'm looking for the average one.

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And then I want to set it equal to whatever property I'm looking for.

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So I want to get the average on what?

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Well, I want to get the average on the rating, correct, so rating is the one that's changing.

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In one case, it's five and the other one, it's one.

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Now how we can set that average while we go here for the property, but we do need to add this.

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I'm sorry to say here a rating and run rate should return.

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Three.

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Why?

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Well, because they have five and one.

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You can see it is getting Colquitt.

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And then lastly, I want to get the number of reviews again of these properties.

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The only reason why I'm naming this way, because that's how we have them in the product.

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But remember, whatever we're getting back here, this is what we're setting up ourselves.

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Correct.

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So and here we just use the operators.

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But as far as the keys, I'm setting them up myself.

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Let's go here with number of reviews viewers allowed is equal to you.

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We'll set up the curlies now.

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Use another operator.

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We'll go with some index if you want to just some of them up.

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If so, that equal to your one.

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And now check it out.

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I have an average rating a number of years and I get the values.

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I fully understand that probably the idea is the most confusing one.

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Again, I know I said this before, but the reason why I can add here now is because I already look

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for the entire list.

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If you're going to have some kind of property that the value is actually changing because keep in mind

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that for a product, the value is not changing.

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Therefore, I can either go with it now or I can actually set it equal to product.

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It doesn't really matter.

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Just keep in mind that the syntax would be following where you are looking for a product and then notice

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them.

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My value did not change because you need to keep in mind that I'm grouping them by that ID value.

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And since the add value is exactly the same, therefore the result is exactly the same.

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But if you want to group them by something that is changing around, you'll get multiple values.

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And again, this is something that you can clearly see in a box.

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That's why I don't want to go out of the way and start setting up some kind of wannabe example because

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you can clearly read this option in a box and once we have all of this in place.

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Now let me go back to now.

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So I'm going to go here with, no, I run if we want to get the code.

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Essentially, if we want to just get the code snippet that we can use in our code base and we can simply

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go to export pipeline.

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We're not looking for a python for the node.

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And then let's also add both of these like so.

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And what you're looking for here is not the MongoDB, not the driver and all that what you want or here

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is this one, the aggregation.

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Now, in my case, like I said, we'll start everything from scratch regardless because there's more

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functionality that you run on.

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So I suggest pretty much just either taking this whole thing.

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Maybe let's do it this way and then let's navigate back to our project and let's set up a temp file

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where we have the models.

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So on here, I would just say temp and jazz, and let's copy and paste again.

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We're not going to use this functionality.

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We're literally just looking for disarray.

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That's the only thing we want over here.

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So for the time being, we'll just save it.

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So that's how we can set up aggregation pipeline in the glory, in the graphical interface.