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Let's run our first geo query. For that I'll work with my places and I want to find places that are near

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my current location.

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Now what is my location? Now

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always keep in mind

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that of course rarely we'll work with the shell as we do, most of the time,

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you'll write an application that does what we are now doing with the shell or then it will do that with

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its driver of course.

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So therefore you might have a web application where users can locate themselves,

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you can do that through some web APIs or you have a mobile app where users can locate themselves. Such

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location APIs will always return coordinates in the form of latitude and longitude,

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this is the standard format.

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So your application will give you some latitude and longitude data for whatever your user did,

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for example locate himself.

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Now let's fake that part,

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so let's simply click somewhere, here for example and now I marked a place where we also see the coordinates.

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If I click on that, I can also copy them from there. Again,

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the second coordinate is the longitude, first one is the latitude. So this is the location we assume

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we're getting from our app,

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so how can we now use that location to find out if this place here is near our location and what does

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near define?

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Well let's see that step by step. In find,

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I definitely want to have a look at my location key and if you named that differently, you need to name it

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differently here,

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this is not a reserved keyword,

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this is simply referring to our key here

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and then here, the value is a document where I use $near, 

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$near is one of the operators provided by mongodb for working with

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geospatial data.

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$near requires another document as a value and there,

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you can now define a geometry for which you want to check if it's near,

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so $geometry. That again is a document

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and this now again describes a geo json object, so we could check here if a point we add here is close

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to our point and that's exactly what I'll do.

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So since we have to pass in some geo json here, I can add a type and that type will also be a point,

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we'll work with different types later by the way and I will pass my coordinates, just as before because

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this has to be geo json,

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we have to have a type here which is one of the valid types and we have to have coordinates here.

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And you therefore of course also know which format coordinates should be in, correct

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it should be an array where the first value is the longitude,

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second value is the latitude.

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So let's paste in that longitude we grab from Google Maps and let's then also grab the latitude

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and let's paste this as a second value.

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Now if I hit enter, I get an error and the error is telling me that it's unable to find an index for

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the geoNear query and geoNear is simply the behind the scenes name of our near query.

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So for this, we will need a geospatial index for this query to run.

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Not all geospatial queries require index but they all just as with other indexes will most likely

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benefit from having such an index,

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so let's add a geospatial index in the next lecture.