You pass a number It will reduce the number of partitions You can resize it because you have to calculate this But in this example assume you know that See now if you look at the later second partition is empty The partition has only one line That’s also not so So I’m assuming that I want only to so I can help spar Take this really applies Coil is kept order later but really to partition on TV I want a little so it will just bring it into partitions now So you have to do tests so normally What you Is that your sample it for example just examined If you’re having one terabyte of data right and you take a good sample of that data let’s say NGV 400 GB and you’ll run it once So then you can understand you know after the filter.
Okay you can call a collect action So let’s say after the first that I want to see that if I can do it So I know that orders only I’ll order Let’s say I don’t know one GB rate or 10 GB later After the filter When I get the date it’s only five That means half is reduced so I can calculate Okay if I’m loading one terabyte off later I don’t have to manage this many Jae beam So after this step I should call the qualities I can go So there are two are transformations coyly Sandri partition coy Little always decrease There is no way you can increase if you want to increase You cancel the partition from four Probably you want to go to eight Maybe you want to increase the processing power No let’s say I want to divide it for their I have probably some J b m three.
Okay So I can increase the repartition of the data so I can say from four I want eight so I consider leave partition in the bracket I can see it So even though if a partition is empty the baby and we’ll keep it there’ll be no daytime the partition But it will remember that I have a partition Corp Even there is nothing So so the envelope deleted Yonville thing There is something inside it Young cannot actually go inside and see whether you have something there I told you that initially when you’re creating the artery right So I say you mentioned in partition Okay You asked what went big on Dana Only then will be created Tony will be ideally idea Nothing will be there Then it’ll be live here You have to manage it What qualities To reduce us actually Okay so now you have two partitions actually because we just wanted to optimize the court.
So now you have four I set the partition eight Okay well read the whole later Do a full shuffle and just give them on eight partitions Now since you have asked this much re partition can also be used to decrease the number of partition Coil is actually intelligent because if you’re doing police okay what will happen is that this message might go here This message might go here or there and we just delete these two If I’m doing a coil is there is very minimum data movement If I don’t re partition to go for a chauffeur meaning from here I can say re partition too It will do it for me But before doing that read all this data onto the ram and go for his suffering their little radio So that is maximum data moment and re partition So I really to reduce your number of partition you squeeze to increase There’s only one way that is re partition There is no other way you can use now The most important point surprising to is that let’s say you wrote a spark or in which you wrote these three lines create an rdd filter the rdd you said oil lease and you say learn nothing will happen This is the surprise.
Actually, you wrote a spark or where you wrote all these three lines okay Read from a CIA first filter error message Then you set oil lease and you submit the job That list of nothing will happen in the cluster because all of this is lazy There is something or lazy execution Meaning spark will not start execution unless you call something called an action These are transformations Meaning you’re changing the later But you are never saying that Show me the output right You are saying repartition that it filters the data Okay So what Where are you saying Show me the output You’re not doing that So unless you call something called an action where you say that Jew me thou put nothing will work to do that you can call an action call Collect Collect is a most common action inspired.
The new call collect Okay You’re telling spark that I want to see the final outward That’s it So collect will look at this cleaned our duty So you are asking to Give me the output of this plane Daddy and Spark will understand if I want cleanly hearted I should have another side Really The 500 started I should read first It’ll go to your hard disk reader data Do all this stuff on Then show this is the output I show this on your screen on then the entire pipeline is empty Spot never keeps your date a memory once the processing is over Okay You got the results on his screen like this.
You’re so everything is gonna know our duty Nothing Is there no card In a nonpartisan nothing will be there Everything is going So only for that split second all these things happen So if you call it collect here you will see this output Okay Now if I want to know whether I should read honoree partition what I should do is that I should go back here Okay I will do uh save off the Sarah you can all sort of a sale Mr. Oren are really when you say stable to save us a file our next fight So I will say save as an action on this field that rdd and then I particularly the size like my orders in our latest n j B After the filter it is fig b So the process fi G b I am launching this many things so I can be right My court in that so collect will simply display output on the screen That is also an action called Save as text File.
Okay, I’m not uh just talking I’m showing stuff So if it is tech state-aligned by Landel partition that’s what’s on The same logic is applied because if there is a line which is divided between two partitions little calculating port split saying logic off-map it is applied here Now his question was What if I don’t want to do it So he had a very good question So he’s asking So the problem with this is if I run the spark or in a split second everything will happen And then I see the output on my screen No are really nothing is there in the memory Because the this is scored bag director A cycling graph sparkle creator Dad a graph of execution and perform Stefan’s to post a priest a four-hour result And then everything is gone again You’re on against Lord that’s a different.
So collectors in action where you return all the elements in the driver program meaning you see that you can also say save aspects trial There is an action Uh that will save See Save aspects trial If I say save as text file for an r Really whatever data is there and rd it’ll save us a text file so I can see that in our group or wherever you’re starting it right now Is this the only action available No I have to save Aska Sandra Able or many other ways to save the data Ideally X file save you go to just to see the later Okay So in the initial face-off reading their data even my producers park Everything will be saying because it is blocking you are reading nor difference it makes once the data is available in memory Then their difference comes. After all, here you see view dinner filter then words that oil lease on.
Then let’s say something else or severely for doing all this The data is still in the memory You’re not writing anything but there is no intermediate yourself You’re pushing too hard This once you call to collect you can write 100 functions and then call collect or that manipulation will happen Final the collective level this place that is a speed So there are many actions or let’s say collect and say what’s next will collect these one actions I cannot say collect on safe sex No So first is collecting will run again If I say a mass text file again the whole operation has to start So you will be wondering is that way I can improve it I will show you OK so probably that is his question So um here I will show you this So once you execute executor the Dag bag is nothing but a director As I click graph it is a fancy way of saying spark creates all the steps to be executed in a graph for men And I will practically show you the bag in the wrong spot Job.