1
00:00:02,130 --> 00:00:08,240
Now our query failed because we had no geospatial index. We need one for the near query here,

2
00:00:08,400 --> 00:00:11,070
so how can we add such an index,

3
00:00:11,070 --> 00:00:12,620
it's pretty straightforward.

4
00:00:12,660 --> 00:00:19,920
Just as with other indexes, we use create index to add such index and then, we add the index on the location

5
00:00:19,920 --> 00:00:23,080
field because that is where we store our geo data

6
00:00:23,100 --> 00:00:27,040
in this example, again if you named that field differently,

7
00:00:27,090 --> 00:00:28,560
definitely use your name here,

8
00:00:28,560 --> 00:00:29,540
you have to.

9
00:00:30,000 --> 00:00:33,630
And then the type of the index is now not 1 or -1,

10
00:00:33,630 --> 00:00:35,970
we don't sort it ascending or descending,

11
00:00:36,090 --> 00:00:39,150
it's also not text because it's not a text index,

12
00:00:39,150 --> 00:00:43,870
it's a special 2D sphere index, written like this,

13
00:00:43,870 --> 00:00:49,020
whoops, not like this, like this, 2d sphere in quotation marks.

14
00:00:49,020 --> 00:00:53,180
With this, we created a geospatial index on the location field

15
00:00:53,190 --> 00:00:59,430
and now if we repeat that query from before, it does succeed and we can also pretty print that and we

16
00:00:59,430 --> 00:01:02,520
see that it found this one point.

17
00:01:02,650 --> 00:01:06,630
Now it found this one point but that doesn't really tell us too much,

18
00:01:06,630 --> 00:01:08,840
it's near the location we added

19
00:01:08,970 --> 00:01:11,210
but how is near defined?

20
00:01:11,670 --> 00:01:14,740
Well near doesn't make much sense unless we restrict it,

21
00:01:15,000 --> 00:01:21,990
so typically what you would do is you would not just pass a geometry to near as we're doing it here but

22
00:01:21,990 --> 00:01:28,620
you would also pass another argument and define a max and maybe also a min distance.

23
00:01:28,620 --> 00:01:32,070
Now max distance is simply a value in meters here,

24
00:01:32,070 --> 00:01:36,810
so if I define like 30 meters, I should actually not find anything,

25
00:01:36,870 --> 00:01:41,660
we can also add the min distance and say it should at least be 10 meters away.

26
00:01:42,030 --> 00:01:47,850
So if I add this, I actually don't find anything and that makes sense because if we have a look at Google

27
00:01:47,850 --> 00:01:52,520
Maps, this is the place, the California Academy of Sciences

28
00:01:52,540 --> 00:01:53,780
and this is where we are

29
00:01:54,050 --> 00:01:56,390
and that seems to be a bit further away,

30
00:01:56,570 --> 00:02:01,430
we can actually measure the distance by right clicking onto the map and measuring a distance and then

31
00:02:01,430 --> 00:02:08,640
if I click here, I can measure the distance to the California Academy of Sciences and it seems to be

32
00:02:08,640 --> 00:02:13,030
around 435,36 meters.

33
00:02:13,260 --> 00:02:18,310
Let's validate this by repeating the query and I'll set the max distance to 400,

34
00:02:18,360 --> 00:02:26,750
so this still should not suffice and it does not. Now if I set it to 440, looks like a little

35
00:02:26,750 --> 00:02:30,230
bit off of my place, so let's set it to 500

36
00:02:30,380 --> 00:02:32,070
and now we find the place,

37
00:02:32,090 --> 00:02:37,440
so now we are within 10 and 500 meters and therefore, we find our favorite place.

38
00:02:37,520 --> 00:02:44,750
And this of course is a great query because it allows us to find out which places are near us in a certain

39
00:02:44,750 --> 00:02:50,070
radius which of course is off my question you want to answer in an application.