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about 90 of smart Madrid's distributed


database and distributed in a weird way


it stores the same data on all computers


and the good thing about aetherium is


that you it's not a database for data


but it's also a database for code you


can create you can write a code and


store in a theorem the code is called


smart contract and a smart contract is


basically a number of functions and some


place to store some data but you you


can't randomly change this data once


you're already uploaded it to etherium


you can only change this data according


to functions you wrote when you uploaded


this code to ethereal so when you need


to change your your smart contract data


you just create a transaction which do


changes according to function and it's


simply like : this function one good


thing about smart contracts is is well


people imagination and people just


invite very very funny way to use smart


contracts they they decided that we can


use smart contracts to kind of create


our own currency and how it works


basically we create a smart contract


which has some mapping it data mapping


from addresses to value and it says that


some address have some some some amount


of tokens or some amount of this


currency and yes then everybody can


create a transactions which change this


mapping


into our functions and we can write very


interesting things we can write basic


things like for example if I create a


transaction to a theorem which works


according to a mid function it well this


function basically adds adds some value


to my balance and we can transfer this


tokens or we can like do other stuff if


you want to learn more about this you


can go to a theorem work they have a


good tutorials and yeah you will end up


you will end up written your own talking


your own currency and you even can


launch a saw and if you launch I saw


come to Belarus because it's actually


legal legal to do it in Belarus thank


you thank you so hi some months ago I


had an idea which actually uses the


project and just wanted to quickly


present it so it's not a jam or anything


it's just technique I used to do some


stuff so I have this had this bus and I


wanted to drive it I'm just kidding so


essentially what it is in my previous


talk I talked about commands and events


but I haven't talked there is a funny


way to decouple things but do I mean


well this is just a small code example


which says ok this is how do we register


things or command handlers to come


handle commands so you just built


something like this it's very simple you


add stuff to the registry and you can


fetch stuff from registry for events


it's the same except events can be


handled by multiple handlers as opposed


to commands which can be handled by just


a single one so it's a tread same thing


so how we have a registration phase


which happens at boot time


so before we boot our application we


register all of our command handlers


like this


and all of our event handlers like this


this is just as an example and then we


have execution phase so in order to


handle command we just said ok bus come


on please handle my command or we want


to handle an event and it's the same


thing


bus event please handle my event why


because coupling handlers are registered


in boot time publisher needs not know


what if anything will handle the message


just tell the bus to handle it


handlers do not care where messages


coming from and interacting parties are


completely decoupled is this a good idea


I don't know it's a pattern it's used


sometimes but if you have an opinion


please tell me here thank you very much


so I was talking about refinements and I


started to show some use cases when he


might be willing to use it so I already


told about the balance reduction


examples so the next thing I was started


talking about but I was stopped so it's


kind of modernization so if we want to


use some features they're not available


and older rubies or maybe in older


versions of frameworks you want to


integrate with you can do this simple


trick but let's go further next example


is a kind of perfect privacy so in Ruby


we private keyword actually doesn't make


your code private so safe from invoking


from other places so we you always can


do something like send and that's it


but with refinement you can actually do


that I don't know when you need it but


that's a kind of feature of Finance Oh


the most common use case is to build


their cells using refinements to pollute


our global namespace but just within


this one file that's an example from gem


called


but earn much think so it's a trying


people try always try to build Alex


Ephraim Ruby one more example from one


of mine gems so it's just a synthetic


sugar to convert our lambdas to brats


and everyone knows that lambent process


broke sorry


two different things yeah and there's


very subtle differences and sometimes we


don't want to care about it and use only


perks and of course a lot of syntax


sugar could be possible with refinements


and actually just kind of broad tip you


can use information about activated


models with refinements it is the models


which I included with using kooky word I


don't know where you need it


but that's a feature of the language we


have almost no one you know about it and


just as a quick bonus I guess most of


you heard about Rafa will be yet another


promising implementation and it supports


refinements already so that's a sign


that refinements will be in the language


for a long time I think because


otherwise I don't see what why they


decided to waste time on it and of


course refinements had some problems


well let me show just a few of them well


there are a lot of kind of tickets and


the Ruby issue tracker which and not


exactly bugs but strange behaviors when


some conditions requirements do not


behave as people expect and there are


some interesting API problems so that's


example that refinement is activated


when you use send but it's not activated


when you use public send that's kind of


weird things so do know that and if you


use their finance and there of course


promise without implementations for


example with JRuby the behaviors


sometimes you need to you know look for


workarounds if you want to use your


fireman's but overall they works


let's all at the end of my talk I know I


got it mean it's okay


and I want to tell you about as a


project of mine which is called Jam


check and actually all this stuff about


refinements it's a part of this broader


project that's a collection of kind of


tips for first of all for Jam offers so


including this tip with my monkey


patching I don't know how to open


browser there so sorry please go to that


page finance I'll share a link later so


it's kind of checklist which I built


going to my own experience which helps


me to you know write better software for


developers so it's not for writing


commercial applications but for writing


gems for other developers make it easy


to use this and gems to extend them and


whatever there are some crucial


properties that I think every time she'd


have almost no gems that help all of


them even my gems of course I don't


follow all these rules but that's my


attempt to you know to help others to


build better software there are a lot of


useful links to useful tools which helps


you to do better documentation you know


better linting tools and etc so that's


it and since I have one second thank you


and goodbye


okay please raise your hand if you feel


like you're being distracted from your


real work too often okay okay and please


now raise your hand if you you're the


person who distracts yourself by


browsing Twitter doing girl and stuff


okay great have you heard that


distractions make actually dumber than


being stoned no now you know okay so I


want to tell you how to become smart


again so I try to eliminate distractions


but I couldn't so I found a way to come


tain them and here's how so can I have


my sandwich it does one think you


remember from the stock this is sandwich


okay


offline sandwich offline sandwich now we


can go or stay and remember this


workflow okay so first offline then


online and third step of topic so it's a


way to organize your workday


then repeat it's like let's say around


you'd have like four rounds let's say a


day where first you work on your real


job you put your you turn off your slack


you turn off your phone


your boss cannot call you you do the


real job like let's say one hour or 90


minutes this is the time where you can


code where you can actually investigate


some stuff then when you're done you


enter the online face or around where


you can actually communicate with your


colleagues you can check what they wrote


to you you can write them what you are


doing and you actually should do it so


this is the focus face and this is the D


focus face because sometimes the problem


is your focus too much and you only see


this formatting problem and you can be a


little deluded sometimes then of topic


face the best face you can browse


Twitter you can go for a coffee


I suggest like let's say 30 minutes for


online face and whatever you think is


right for off-topic face and then repeat


so you can already see the sandwich


somewhere ok so does it make sense a


little bit and I can actually say that


it brought my brain


back to face where I felt it has some


more capacity because like when you're


being disrupted all the time you'll you


actually feel Dumber at least this was


my this was my feeling oh there's still


two minutes so let's continue okay


another way to to call it would be like


immersion driven workflow so you


actually immerse yourself in such


offline face no one can see you


immerse like going underwater or you can


call it like put yourself into a little


jail for some time


yeah and now you do the work you cannot


escape and the goal would be at the


beginning of the offline face to know


what you want to do establish the plan


yeah


put it in paper or whatever and try to


accomplish something during the face so


a comet or a write-up why you don't want


to do it or like the result of the


investigation so don't just quit when


the time is over just try to accomplish


something and then you get the instant


gratification which is the primary


reason that we look for distractions


still one minute okay but it might not


work in your workflow work environment


it works best if you got remote work


environment it works even better if your


eyes asynchronous and it works best if


you got remote asynchronous and autonomy


when it comes to your work so you might


go to your boss and convince convince


him to do all of that so that's it thank


you


so in this lightning talk I want to take


a little step back and talk about Ruby


standard library and I decided to go


through it and find and see what and


what I can find there and here are some


of my findings so for example you have a


brief class which lets you to find


abbreviations for a bunch of strings


that are not ambiguous this is obviously


very useful thing and you have it with


every Ruby distribution out there next


thing is matrix this might be a bit more


useful so just for regular operation on


matrices just like you would expect to


every language to have maybe not in


standard library but Ruby has it then


primes again some math and you can find


like some prime and in sequence or you


can make prime divisions


that's all also I think you you got


right away with with your rube


distribution okay but let's talk about


some more interesting things so there is


three actually classes DBMS DB M and G


DBM they are differ by internal


implementation only so you need to get


to the docks and find out what are the


differences but in general it's embedded


keys key value store for Strings so for


example if you have huge hash of strings


as keys as values you can upload it to


disk and forget about it let's garbage


collector handle it free up some memory


and when you're ready to work on it


again you can load it and for example


print print what's in there so this is


what you would expect because this is


exactly what you you written in in the


beginning so this is also for free


next thing is P store this is a bit more


complex stuff because be store lets you


save


a keyaki of objects with their states


etc so I didn't include an


implementation of state class but you


can imagine the system states with a


name connected to other states via some


named labels and you can you can create


all this world and then open MP store


and under that key start because why not


write the entry point that the first


state the starting state and again you


can for example stop stop the script and


come back later at some point and just


read it and everything you did was there


and you can you can still have all this


hierarchy up and running of course it


does not work for literally everything


but everything that can be marshaled


using using Ruby standard marshalling


and can be saved and retrieved


another thing is distributed through B


this is this is a bit more complicated


but really cool you actually create an a


class an object and expose it via the


Ruby protocol to the outside world so in


a separate process you can connect to it


and just change its instant variables


called methods whatever you want there


is option parser which is for parsing


options from CL layer CLI and this is


quite quite convenient more than


environment variables and of course


there's much more


for example topological sorting of


directed graphs and finding strongly


connected components that's also Ruby


standard library so if you have some


time go there read it maybe you will


find some use case for them I don't know


I haven't thanks alright so I wanted to


show you how I play games with Ruby so


first show of hands how many of you


actually own a desktop computer ok how


many of you play games not on this


computer but you know


okay cool so it all started with the I


wanted to play black and white too on my


desktop computer and it was running


Windows 10 and it nothing worked so


first I try to just install the game in


Windows 10 didn't work because it needed


an emulation layer to combat piracy and


that has been removed in Windows 10 so


it needed Windows 8 and at the months to


install that on my computer so then I


try to install the game inside VMware


Workstation because it can emulate the


GPU didn't work either because it lacked


and it's an emulation layer so that was


probably why so then I complicated the


whole setup I installed a human EMU and


I used two different graphics cards I


used two networks cards and two screens


and that worked so in Linux does


something called PS I pass through PCI


pass through and using the beefy our


driver and that basically says these


graphics cuts I want to put this driver


into it and that tells the operating


system to leave it alone that means that


when you actually plug that in Linux


won't try to display anything on them


and it tells it maybe I want to use this


formulation so basically what you can do


is that you can have a lot of different


graphics cards so some of the CPUs


actually come with a little graphic card


in it you can run Linux and that I


didn't have then you can actually have


two keyboards or three keyboards 3


Mouse's and you actually start playing


games inside of multiple guest operating


systems but you can still use the same


mainboard so this is the how I run my my


stuff I that's a lot of stuff here so


basically you want to do the clock


apparently in in virtual machines that


makes the compute


so you want to like use the real cloud


for the app you want to put in all the


USB devices you want to tell you can see


the device vio PCI you want to tell them


with graphic cards to use and in the end


you want to just say use this steam disk


down here and that's why I have all my


games on and this becomes very


unmanageable very quickly because you're


kind of like oh I need a new virtual


machine so what do you do oh you just


cook the best file and then you run it


somewhere else and then at some point


when you buy a new USB device like this


I use all of this all of them have the


the keyboard but sometimes I want to use


my headset sometimes and you want to use


my goggles sometimes I want to record


something so I have to attending a


meeting so once you use my microphone


sometimes I want to talk in my control


for my for my drone and so I want to


have a standard way of doing this


so I was thinking hmmm this is not


that's not enough I don't want to just


use like boots and gets into the rubic


command line because I want to try


something new new it's 30 years old I


use curses and I thought ok it's good


enough for the standard librarian rupee


so it's good enough for me


and then I can use something cool like


easy but now it was removed from the


standard library so to go in and like


find the gem and put that in but it


actually worked so you can do like like


this you can like start the curses Chris


interface you can like do all this kind


of stuff you can see I'll put the cursor


here and I write this stuff and it works


but it's very annoying to work with 30


years old like uses YX and even in the


documentation here it says X Y here you


have the window the windows uses x and y


four columns and lines but the whole


thing but you actually ask how much this


is available in your terminal it uses


columns Alliance what come on just maybe


make a rap or something like that but


now if this is what you have to deal


with attribute off says that it turns an


attribute turns on an attribute


and attribute on sets it turns it off


what and it actually works as you expect


so I don't know who wrote this so


yesterday we had an example of heavy


heavy application in rails so I


replicated that so we have like lists of


hundred products and with some ratings


so actually we can see that the page


loads like thirty hundred three 300


milliseconds so it's heavy right


so what we have here so we have a


standard products controller with a


limit of 100 products we have a template


we display a product name product and


fancy stars from product rating I mean


in product rating we have in product we


have this this method that calculates


the average rating for for each product


so looks like a legit recode so what's


wrong with that so let's take a peek


under the hood so i refresh the page and


whoa what's going on yeah and that's the


reason of the slowness so so first we


load somewhere here I hope you see


everything clearly so we select 100


products and then on the view we for


each row on the table we execute two


queries so first we check if there are


any product reviews if there are then we


calculate the average so Wow so what we


can do about about this so let's let's


take a look at some SQL I hope you like


it


so the classic approach is to oxo a


product name and then under round of


average of product reviews


and that writing casted to integer from


product joins product reviews on the ID


columns group by product ID order by in


the average rating and living 10 so so


so what this this query returns is the


top 10 top rated products from the from


the table so I have a data set of you


have here some stats so I have two


thousand products two thousand users and


generated some random reviews we have


three hundred thousand reviews in the


database so this query


works fine execute 140 milliseconds so


we can go where so we can use a common


table expression which is available from


Posterous eighty five point four and


from and and on I don't know if any


older version supports it so first we


calculate at like virtual table of the


average ratings then we create this join


and with the limit so the time is a bit


better


99 milliseconds so it's like two-thirds


of the first query but we can use


another technique which is available


from Posterous in nine point three and


on which is what are all join so here we


have we select from products table and


we write a lot of lateral call in which


we like simulated the join so so we


select the product ID and approach


writing from product reviews where


there's the earliest so PR is product


reviews where the product idea on


product reviews equals the product ID


which refers to the outer table


and we then we order but in the rating


and limit the time is similar to the to


the previous query but that's not at the


end of the story so because we don't use


any filtering on oh my god so when we


use a filtering so classic approach we


are better 47 milliseconds with the


common table expression there is no no


difference because the the calculation


of averages is made up front so so it


takes the whole time but with lateral we


dropped into five milliseconds so the


conclusion is that after the the


optimization the page load is 37


milliseconds thank you