1 00:00:00,940 --> 00:00:02,720 ‫So we learned about Document 2 00:00:02,720 --> 00:00:05,860 ‫and query middleware, and now the last middleware 3 00:00:05,860 --> 00:00:09,033 ‫that we're gonna talk about is aggregation middleware, 4 00:00:10,560 --> 00:00:12,253 ‫and as you can probably guess, 5 00:00:13,168 --> 00:00:14,930 ‫aggregation middleware allows us to add hooks 6 00:00:14,930 --> 00:00:18,350 ‫before or after an aggregation happens, 7 00:00:18,350 --> 00:00:19,970 ‫and so let's now actually continue with 8 00:00:19,970 --> 00:00:23,830 ‫our previous example where we did hide the secret tours 9 00:00:23,830 --> 00:00:27,540 ‫from the queries, now in an aggregation the secret tours 10 00:00:27,540 --> 00:00:30,270 ‫are still being used, right? 11 00:00:30,270 --> 00:00:32,220 ‫So let's quickly confirm that actually, 12 00:00:33,840 --> 00:00:37,290 ‫for example here in our gets tour stats, 13 00:00:37,290 --> 00:00:39,940 ‫so that's where we used the first aggregation 14 00:00:39,940 --> 00:00:42,700 ‫and so you see we have four tours here, 15 00:00:42,700 --> 00:00:45,500 ‫four in easy, and three in medium 16 00:00:45,500 --> 00:00:49,060 ‫and so that makes 11 but we already know 17 00:00:49,060 --> 00:00:52,480 ‫that we actually only want 10 tours. 18 00:00:52,480 --> 00:00:55,380 ‫So there are 10 tours that are not secret, 19 00:00:55,380 --> 00:00:58,900 ‫and one that is secret, and so now we get all these 20 00:00:58,900 --> 00:01:01,880 ‫11 tours here and so basically we also want 21 00:01:01,880 --> 00:01:05,000 ‫to exclude the secret tour in the aggregation. 22 00:01:05,000 --> 00:01:06,373 ‫So how could we do that? 23 00:01:07,430 --> 00:01:09,680 ‫Well let's take a look at where our aggregation 24 00:01:09,680 --> 00:01:14,680 ‫is actually happening so it's down here in yeah, 25 00:01:14,900 --> 00:01:19,270 ‫so in get tour steps, and so what we could do is to here 26 00:01:19,270 --> 00:01:22,640 ‫in this match state simply exclude the secret tours 27 00:01:22,640 --> 00:01:24,520 ‫that are true right? 28 00:01:24,520 --> 00:01:26,740 ‫So that would be quite easy to add here, 29 00:01:26,740 --> 00:01:29,080 ‫but then we would have to add the same thing 30 00:01:29,080 --> 00:01:32,080 ‫down here in the other aggregation that we have, 31 00:01:32,080 --> 00:01:34,680 ‫and if we had even more aggregations we would then 32 00:01:34,680 --> 00:01:37,860 ‫have to add that in all of them and that's of course 33 00:01:37,860 --> 00:01:40,560 ‫not a good idea, because for example we could forget 34 00:01:40,560 --> 00:01:44,010 ‫to do it and it's also just repetitive code 35 00:01:44,010 --> 00:01:48,820 ‫and so let's simply exclude it right at the model level, 36 00:01:48,820 --> 00:01:53,280 ‫alright so let's add aggregation middleware here 37 00:01:54,470 --> 00:01:55,893 ‫starting with a comment. 38 00:01:59,450 --> 00:02:03,970 ‫So aggregation middleware and so just like before 39 00:02:05,070 --> 00:02:10,040 ‫we have tourSchema.pre so we want this to happen before 40 00:02:10,040 --> 00:02:12,110 ‫the aggregation is actually executed 41 00:02:13,060 --> 00:02:16,573 ‫and so here we use the aggregate hook. 42 00:02:18,230 --> 00:02:22,047 ‫Alright and then our function which again accepts 43 00:02:22,047 --> 00:02:26,332 ‫the next function so calling the next middleware. 44 00:02:26,332 --> 00:02:31,332 ‫Alright, so let's start by taking a look 45 00:02:32,530 --> 00:02:37,113 ‫at this, so remember that up here in query middleware 46 00:02:37,113 --> 00:02:40,283 ‫that this object points to the current query. 47 00:02:41,130 --> 00:02:44,590 ‫Then here in document middleware the this object 48 00:02:44,590 --> 00:02:46,850 ‫points to the current document, 49 00:02:46,850 --> 00:02:50,330 ‫and so down here in aggregation middleware 50 00:02:50,330 --> 00:02:53,880 ‫this is going to point to the current aggregation object. 51 00:02:53,880 --> 00:02:56,764 ‫Okay and so let's take a look at that in the console 52 00:02:56,764 --> 00:03:00,113 ‫but before that let me just remove this log here. 53 00:03:01,590 --> 00:03:05,890 ‫Alright give it a save, run this aggregation here 54 00:03:08,520 --> 00:03:12,520 ‫and that's taking a lot of time and so let's cancel it 55 00:03:13,750 --> 00:03:16,580 ‫and go back and that's probably because 56 00:03:16,580 --> 00:03:21,460 ‫we're not calling next here, and so like we already know 57 00:03:21,460 --> 00:03:23,580 ‫we get stuck in the middleware function 58 00:03:23,580 --> 00:03:26,340 ‫and so that's not good. 59 00:03:26,340 --> 00:03:29,063 ‫So let's try that again now send, 60 00:03:30,120 --> 00:03:33,490 ‫and yeah so now we're back and now let's take a look 61 00:03:33,490 --> 00:03:35,470 ‫at the aggregation object. 62 00:03:35,470 --> 00:03:37,700 ‫Okay so there's a lot of stuff in here 63 00:03:39,980 --> 00:03:43,800 ‫so it's not really interesting here 64 00:03:44,950 --> 00:03:48,330 ‫and I cannot really find what I'm trying to show you here 65 00:03:48,330 --> 00:03:53,330 ‫and so let's simply add this.pipeline okay because what 66 00:03:53,450 --> 00:03:57,140 ‫I really wanted to show you is just the pipeline object. 67 00:03:57,140 --> 00:04:00,620 ‫Okay, and actually it's pipeline like this 68 00:04:00,620 --> 00:04:03,053 ‫so it's actually a function, a method. 69 00:04:04,970 --> 00:04:06,593 ‫So let's clear the console here. 70 00:04:07,820 --> 00:04:12,820 ‫Try this again, and so here we get the aggregation pipeline, 71 00:04:14,350 --> 00:04:17,620 ‫and so that's simply the array that we passed into 72 00:04:17,620 --> 00:04:19,770 ‫the aggregate function before. 73 00:04:19,770 --> 00:04:23,040 ‫Right, so let's take a look and so here we have 74 00:04:23,040 --> 00:04:26,400 ‫that array, this one not this one. 75 00:04:26,400 --> 00:04:28,200 ‫So we have the match to group 76 00:04:28,200 --> 00:04:30,910 ‫and then the sort so if we take a look here 77 00:04:30,910 --> 00:04:34,470 ‫at the console we have indeed our match with the ratings 78 00:04:34,470 --> 00:04:37,320 ‫average we have group and then sort. 79 00:04:37,320 --> 00:04:41,020 ‫So that is exactly the pipeline we specified before, 80 00:04:41,020 --> 00:04:44,570 ‫and so now in order to filter out the secret tours 81 00:04:44,570 --> 00:04:47,970 ‫all we have to do is to add another match stage 82 00:04:47,970 --> 00:04:50,700 ‫right at the beginning of this pipeline array, 83 00:04:50,700 --> 00:04:53,713 ‫right and so let's do just that. 84 00:04:55,029 --> 00:04:58,040 ‫So let's do that here before this log, 85 00:04:58,040 --> 00:05:03,040 ‫so this.pipeline and remember that this is an array 86 00:05:03,890 --> 00:05:06,130 ‫and how do we add an element at the beginning 87 00:05:06,130 --> 00:05:06,963 ‫of an array? 88 00:05:08,262 --> 00:05:11,510 ‫We use unshift and so that is a standard JavaScript 89 00:05:11,510 --> 00:05:15,340 ‫method for arrays okay, we have also shift to add 90 00:05:15,340 --> 00:05:18,470 ‫at the end of the array and unshift at the beginning 91 00:05:18,470 --> 00:05:21,690 ‫of the array, and so again what we want to add here now 92 00:05:21,690 --> 00:05:25,490 ‫is to add just another stage, so very similar 93 00:05:25,490 --> 00:05:26,803 ‫to what we have down here. 94 00:05:29,690 --> 00:05:34,690 ‫So match and then secretTour, not equal to true. 95 00:05:40,460 --> 00:05:45,340 ‫Give it a save, and so this piece of code here basically 96 00:05:45,340 --> 00:05:48,330 ‫is exactly what we have up here right? 97 00:05:48,330 --> 00:05:51,220 ‫Basically removing from the output all the documents 98 00:05:51,220 --> 00:05:55,260 ‫that have secretTour set to true, right? 99 00:05:55,260 --> 00:06:00,160 ‫So if you give it a save now, then let's check this out, 100 00:06:00,160 --> 00:06:03,250 ‫and remember we have now 11 tours, four, four, 101 00:06:03,250 --> 00:06:06,780 ‫and three so let's check the result afterwards 102 00:06:06,780 --> 00:06:10,340 ‫and so now indeed one of the difficult yours is gone 103 00:06:10,340 --> 00:06:13,460 ‫so we only now have three difficult tours meaning 104 00:06:13,460 --> 00:06:15,930 ‫that we are back to just having 10. 105 00:06:15,930 --> 00:06:20,260 ‫Okay and actually we can confirm that our super secret tour 106 00:06:20,260 --> 00:06:24,630 ‫was a difficult tour, alright and so that is now gone 107 00:06:24,630 --> 00:06:27,700 ‫and so our results are now only about the regular 108 00:06:27,700 --> 00:06:30,800 ‫non-secret tours alright? 109 00:06:30,800 --> 00:06:34,670 ‫And we can again take a look at our aggregation pipeline now 110 00:06:34,670 --> 00:06:38,640 ‫and here you see that now we have these two matched stages. 111 00:06:38,640 --> 00:06:41,150 ‫Great and as I mentioned before it's no problem 112 00:06:41,150 --> 00:06:45,050 ‫to repeat these stages, we can have as many match stages 113 00:06:45,050 --> 00:06:49,920 ‫as we want, okay and that's it for aggregation middleware. 114 00:06:49,920 --> 00:06:53,740 ‫I'm not gonna include any post code here for middleware 115 00:06:53,740 --> 00:06:56,290 ‫that's not really necessary alright, 116 00:06:56,290 --> 00:06:59,050 ‫and I'm also not gonna talk about model middleware here 117 00:06:59,050 --> 00:07:01,570 ‫because it's really not that important. 118 00:07:01,570 --> 00:07:04,750 ‫Alright, so middleware is some really cool 119 00:07:04,750 --> 00:07:08,180 ‫and important stuff that we can add to our models, 120 00:07:08,180 --> 00:07:10,560 ‫and there is indeed other cool stuff 121 00:07:10,560 --> 00:07:13,430 ‫that we can do with models, for example implementing 122 00:07:13,430 --> 00:07:16,690 ‫instance methods which are methods that will be available 123 00:07:16,690 --> 00:07:19,220 ‫on ever document after being queried, 124 00:07:19,220 --> 00:07:21,410 ‫and that again can be quite handy, 125 00:07:21,410 --> 00:07:23,402 ‫and we will do that later 126 00:07:23,402 --> 00:07:25,570 ‫in the authentication section as well okay. 127 00:07:25,570 --> 00:07:27,940 ‫So I'm gonna leave that for a bit later, 128 00:07:27,940 --> 00:07:30,110 ‫now what we are gonna do in this section 129 00:07:30,110 --> 00:07:34,170 ‫just to finish is to actually add some validation, alright 130 00:07:34,170 --> 00:07:37,070 ‫and so in the next two videos we're gonna talk about that.