Author: admin yep

http://img.youtube.com/vi/lRi1-RYnQ7A/0.jpgQuite a regular task, but not a simple solution: how to order query results by a belongsTo relation column? I will show you one "bad" way, and two good ways to do it.Laravel News Links

https://theawesomer.com/photos/2021/07/giant_plasma_cannon_t.jpg

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If you’ve never seen one, a plasma popper is an awesome-looking device that directs a ball of propane gas through a series of twisted tubes. Charles over at Hacksmith Industries was asked to build a plasma popper, then leveled up the challenge with bigger and bigger versions, culminating with a massive fireball maker.

The Awesomer

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Python is a powerful programming language that is very popular and widely used. It has various real-world applications in data science, web development, artificial intelligence, data analytics, and much more.With so many available resources, knowing where to begin is sometimes overwhelming.

Learning Python can become even more confusing if you do not understand its basic building blocks. Without these fundamentals, you cannot build anything interesting. Luckily for you, though, we’ve compiled a list of free Python courses and apps that you can utilize to kickstart your Python career.

Keep reading to find out where you can learn Python free.

Where Can I Find a Free Python Course?

If you are someone who’s just started learning to code or are thinking about coding for the first time, then you’re going to need to start with the fundamentals. Perhaps you want to learn Python to start working as a freelancer, or maybe you’re thinking about a career change; whatever your reasons, maybe Python is a brilliant and versatile programming language that can help you achieve your personal goals.

For beginners looking for a free Python course, we recommend starting with the basic syntax and programming structure. Once you have acquainted yourself with the syntax, you can learn Python for a specific chosen area of interest.

Related: Coding Apps That Make Programming Easier

You do necessarily need to master Python syntax; this is something that you will learn while working on different projects. We recommend learning Python 3, since Python 2 is an outdated version that is no longer supported.

Here are some courses and apps you can use to learn the basics of Python for free:

• Introduction to Python Programming on Udemy.
• LearnPython.org.
• Learn Python on codecademy.
• Python for Absolute Beginners! on Udemy.

Be careful not to spend too much time learning the syntax, because this is something that you can always come back to. A few weeks of practicing the basic Python syntax should be more than enough. After getting the hang of the fundamentals, you can go ahead and start working on Python projects in an area that interests you.

Learn Python For Data Science

Python is the most popular programming language in data science and machine learning (ML); it can solve complex problems efficiently with the aid of dedicated data analysis libraries. The demand for data scientists keeps increasing exponentially. If you learn Python for data science, artificial intelligence (AI), or machine learning, it will help open many career opportunities for you.

Bear in mind that data science is a vast field, and you need to learn many different skills to have a successful career in this area. These skills can include machine learning, text analysis, social network analysis techniques, information visualization, standard Python libraries such as Pandas, NumPy, and more.

Related: The Beginner’s Guide to Regular Expressions With Python

Here are some free data science-related python courses that you can use to kickstart your career as a data scientist:

• Applied Data Science with Python Specialization: This course specialization is offered by the University of Michigan on Coursera, and will teach you data analysis skills and apply data science methods and techniques. The specialization includes five different courses that cover a range of different data science techniques.
• Python Basics for Data Science: Offered by IBM on edX, this course will teach beginners the basics of Data Science and enable them to work on independent projects.
• Python for Data Science, AI & Development: This course specialization is offered by IBM on Coursera and is comprehensive. It will cover Python basics, data structures, Python libraries, and APIs, and data collection.
• Introduction to Computational Thinking and Data Science: This course is available for free on MIT OpenCourseWare and is a good place for students to understand the basics of Data Science and its application.

Please note that on Coursera, some courses are free and will provide you with a completion certificate at the end of the course. Other courses are paid, but you can still learn for free if you choose to audit the course. If you choose to audit a course, Coursera will not provide you with a completion certificate—but you will have access to the entire course content.

Learn Python for Web Development

Python’s sheer power and versatility make it an incredible platform for web development. You can use Python to create web-based applications in combination with JavaScript. Django (pronounced "jango") is a popular framework for web development and is used to create high-level websites. It is essentially a backend framework for Python and is very secure and easy to use.

Here are some free courses you can use to learn web development in Django:

• Django for Everybody: This specialization is offered by the University of Michigan on Coursera and introduces Python programmers to building websites on the Django framework. The four courses included in this specialization will teach you to build web applications, use JavaScript and JQuery/JSON in Django, and much more.
• Web Programming with Python and JavaScript: This course is offered by Harvard University and dives into designing and implementing web applications with Python, Javascript, and SQL.
• A Beginners Guide to Django at Udemy: This free course on Udemy will take you through the basics of Django and get you started with building websites.

Learn Python Free for Hardware and Robotics

Python is very popular in applications for robotics and hardware engineering. You can utilize platforms such as Raspberry Pi and Arduino for coding with Python.

Here are some courses that can help learn Python for Robotics and Hardware:

• Getting Started With Python on Arduino
• Building Projects With Python on Raspberry Pi
• Raspberry Pi Platform and Python Programming: Coursera

Your Next Free Python Course Is Just a Few Clicks Away

Learning Python is never a bad idea, regardless of your reasons. Coding is a vital skill in the fast-growing technology world of today, and Python is at the center of it.

It is best to start with the basic syntax and then dive into small Python projects. Once you are comfortable with the fundamentals of Python, you should start looking into courses and projects of your interest. Hands-on practice with projects will allow you to master your skills and be a valuable addition to your resume.

MUO – Feed

The FizzBuzz challenge is a classic challenge that’s used as an interview screening device for computer programmers. It’s a very simple programming task but it’s used to determine whether the job candidate can actually write code.

Sound fun and exciting? Let’s get started. In this article, you’ll learn how to solve the FizzBuzz challenge with implementations in 5 programming languages.

Problem Statement

You need to write a program that prints the numbers from 1 to 100 such that:

1. If the number is a multiple of 3, you need to print "Fizz" instead of that number.
2. If the number is a multiple of 5, you need to print "Buzz" instead of that number.
3. If the number is a multiple of both 3 and 5, you need to print "FizzBuzz" instead of that number.

Try to think of a solution to solve this challenge with the help of loops and conditional statements before moving to the solution.

Approach to Solve the FizzBuzz Challenge

You need to follow the approach below to solve this challenge:

1. Run a loop from 1 to 100.
2. Numbers that are divisible by 3 and 5 are always divisible by 15. Therefore check the condition if a number is divisible by 15. If the number is divisible by 15, print "FizzBuzz".
3. Check the condition if a number is divisible by 3. If the number is divisible by 3, print "Fizz".
4. Check the condition if a number is divisible by 5. If the number is divisible by 5, print "Buzz".

Note: You can check if a number is divisible by another number using the modulo operator (%).  For example: 25 % 5 == 0, therefore 25 is divisible by 5.

Pseudocode for the FizzBuzz Challenge

Below is the pseudocode for the FizzBuzz challenge:

for number from 1 to 100:
  if (number is divisible by 3 and 5) then:
    print("FizzBuzz")
  if (number is divisible by 3) then:
    print("Fizz")
  if (number is divisible by 5) then:
    print("Buzz")

Related: What Is Coding and How Does It Work?

C++ Program to Solve the FizzBuzz Challenge

Below is the C++ program to solve the FizzBuzz challenge:

// C++ program to implement the FizzBuzz problem
#include <iostream>
using namespace std;
int main()
{
 for (int i=1; i<=100; i++)
 {
 // Numbers that are divisible by 3 and 5
 // are always divisible by 15
 // Therefore, "FizzBuzz" is printed in place of that number
 if (i%15 == 0)
 {
 cout << "FizzBuzz" << " ";
 }
 // "Fizz" is printed in place of numbers
 // that are divisible by 3
 else if ((i%3) == 0)
 {
 cout << "Fizz" << " ";
 }
 // "Buzz" is printed in place of numbers
 // that are divisible by 5
 else if ((i%5) == 0)
 {
 cout << "Buzz" << " ";
 }
 // If none of the above conditions are satisfied,
 // the number is printed
 else
 {
 cout << i << " ";
 }
 }
return 0;
}

Output:

1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz 22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz 31 32 Fizz 34 Buzz Fizz 37 38 Fizz Buzz 41 Fizz 43 44 FizzBuzz 46 47 Fizz 49 Buzz Fizz 52 53 Fizz Buzz 56 Fizz 58 59 FizzBuzz 61 62 Fizz 64 Buzz Fizz 67 68 Fizz Buzz 71 Fizz 73 74 FizzBuzz 76 77 Fizz 79 Buzz Fizz 82 83 Fizz Buzz 86 Fizz 88 89 FizzBuzz 91 92 Fizz 94 Buzz Fizz 97 98 Fizz Buzz

Related: How to Learn C++ Programming: Best Sites to Get Started

Python Program to Solve the FizzBuzz Challenge

Below is the Python program to solve the FizzBuzz challenge:

# Python program to implement the FizzBuzz problem
for i in range(1, 101):
    # Numbers that are divisible by 3 and 5
    # are always divisible by 15
    # Therefore, "FizzBuzz" is printed in place of that number
    if (i%15 == 0):
        print("FizzBuzz", end="  ")
    # "Fizz" is printed in place of numbers
    # that are divisible by 3
    elif (i%3 == 0):
        print("Fizz", end="  ")
    # "Buzz" is printed in place of numbers
    # that are divisible by 5
    elif(i%5 == 0):
        print("Buzz", end="  ")
    # If none of the above conditions are satisfied,
    # the number is printed
    else:
        print(i, end="  ")

Output:

1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz 22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz 31 32 Fizz 34 Buzz Fizz 37 38 Fizz Buzz 41 Fizz 43 44 FizzBuzz 46 47 Fizz 49 Buzz Fizz 52 53 Fizz Buzz 56 Fizz 58 59 FizzBuzz 61 62 Fizz 64 Buzz Fizz 67 68 Fizz Buzz 71 Fizz 73 74 FizzBuzz 76 77 Fizz 79 Buzz Fizz 82 83 Fizz Buzz 86 Fizz 88 89 FizzBuzz 91 92 Fizz 94 Buzz Fizz 97 98 Fizz Buzz

Related: How to Get Started With Python Using a "Hello World" Script

JavaScript Program to Solve the FizzBuzz Challenge

Below is the JavaScript program to solve the FizzBuzz challenge:

// JavaScript program to implement the FizzBuzz problem
for (let i=1; i<=100; i++) {
// Numbers that are divisible by 3 and 5
 // are always divisible by 15
 // Therefore, "FizzBuzz" is printed in place of that number
 if (i%15 == 0) {
 document.write("FizzBuzz" + " ");
 }
// "Fizz" is printed in place of numbers
 // that are divisible by 3
 else if ((i%3) == 0) {
 document.write("Fizz" + " ");
 }
// "Buzz" is printed in place of numbers
 // that are divisible by 5
 else if ((i%5) == 0) {
 document.write("Buzz" + " ");
 }
// If none of the above conditions are satisfied,
 // the number is printed
 else {
 document.write(i + " ");
 }
}

Output:

1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz 22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz 31 32 Fizz 34 Buzz Fizz 37 38 Fizz Buzz 41 Fizz 43 44 FizzBuzz 46 47 Fizz 49 Buzz Fizz 52 53 Fizz Buzz 56 Fizz 58 59 FizzBuzz 61 62 Fizz 64 Buzz Fizz 67 68 Fizz Buzz 71 Fizz 73 74 FizzBuzz 76 77 Fizz 79 Buzz Fizz 82 83 Fizz Buzz 86 Fizz 88 89 FizzBuzz 91 92 Fizz 94 Buzz Fizz 97 98 Fizz Buzz

Related: The Best Beginner Projects for New Programmers

Java Program to Solve the FizzBuzz Challenge

Below is the Java program to solve the FizzBuzz challenge:

// Java program to implement the FizzBuzz problem
public class Main
{
 public static void main(String args[])
 {
 for (int i=1; i<=100; i++)
 {
 // Numbers that are divisible by 3 and 5
 // are always divisible by 15
 // Therefore, "FizzBuzz" is printed in place of that number
 if (i%15==0)
 {
 System.out.print("FizzBuzz"+" ");
 }
// "Fizz" is printed in place of numbers
 // that are divisible by 3
 else if (i%3==0)
 {
 System.out.print("Fizz"+" ");
 }
// "Buzz" is printed in place of numbers
 // that are divisible by 5
 else if (i%5==0)
 {
 System.out.print("Buzz"+" ");
 }
// If none of the above conditions are satisfied,
 // the number is printed
 else
 {
 System.out.print(i+" ");
 }
}
 }
}

Output:

1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz 22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz 31 32 Fizz 34 Buzz Fizz 37 38 Fizz Buzz 41 Fizz 43 44 FizzBuzz 46 47 Fizz 49 Buzz Fizz 52 53 Fizz Buzz 56 Fizz 58 59 FizzBuzz 61 62 Fizz 64 Buzz Fizz 67 68 Fizz Buzz 71 Fizz 73 74 FizzBuzz 76 77 Fizz 79 Buzz Fizz 82 83 Fizz Buzz 86 Fizz 88 89 FizzBuzz 91 92 Fizz 94 Buzz Fizz 97 98 Fizz Buzz

C Program to Solve the FizzBuzz Challenge

Below is the C program to solve the FizzBuzz challenge:

// C program to implement the FizzBuzz problem
#include <stdio.h>
int main()
{
 for (int i=1; i<=100; i++)
 {
 // Numbers that are divisible by 3 and 5
 // are always divisible by 15
 // Therefore, "FizzBuzz" is printed in place of that number
 if (i%15 == 0)
 {
 printf("FizzBuzz ");
 }
 // "Fizz" is printed in place of numbers
 // that are divisible by 3
 else if ((i%3) == 0)
 {
 printf("Fizz ");
 }
 // "Buzz" is printed in place of numbers
 // that are divisible by 5
 else if ((i%5) == 0)
 {
 printf("Buzz ");
 }
 // If none of the above conditions are satisfied,
 // the number is printed
 else
 {
 printf("%d ", i);
 }
 }
return 0;
}

Output:

1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz 22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz 31 32 Fizz 34 Buzz Fizz 37 38 Fizz Buzz 41 Fizz 43 44 FizzBuzz 46 47 Fizz 49 Buzz Fizz 52 53 Fizz Buzz 56 Fizz 58 59 FizzBuzz 61 62 Fizz 64 Buzz Fizz 67 68 Fizz Buzz 71 Fizz 73 74 FizzBuzz 76 77 Fizz 79 Buzz Fizz 82 83 Fizz Buzz 86 Fizz 88 89 FizzBuzz 91 92 Fizz 94 Buzz Fizz 97 98 Fizz Buzz

Start Your Coding Journey With a "Hello, World!" Program

The "Hello, World!" program is the first step for programmers to become acquainted with a new programming language. It’s considered to be one of the simplest programs possible in almost all languages.

If you’re a newbie to the programming world and exploring different languages, the "Hello, World!" program is the best choice to get started with a new programming language.

MUO – Feed

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MySQL, an open source database developed by Oracle, powers some of Facebook’s most important workloads. We actively develop new features in MySQL to support our evolving requirements. These features change many different areas of MySQL, including client connectors, storage engine, optimizer, and replication. Each new major version of MySQL requires significant time and effort to migrate our workloads. The challenges  include:

• Porting our custom features to the new version
• Ensuring replication is compatible between the major versions
• Minimizing changes needed for existing application queries
• Fixing performance regressions that prevent the server from supporting our workloads

Our last major version upgrade, to MySQL 5.6, took more than a year to roll out. When version 5.7 was released, we were still in the midst of developing our LSM-Tree storage engine, MyRocks, on version 5.6. Since upgrading to 5.7 while simultaneously building a new storage engine would have significantly slowed the progress on MyRocks, we opted to stay with 5.6 until MyRocks was complete. MySQL 8.0 was announced as we were finishing the rollout of MyRocks to our user database (UDB) service tier. 

That version included compelling features like writeset-based parallel replication and a transactional data dictionary that provided atomic DDL support. For us, moving to 8.0 would also bring in the 5.7 features we had missed, including Document Store. Version 5.6 was approaching end of life, and we wanted to stay active within the MySQL community, especially with our work on the MyRocks storage engine. Enhancements in 8.0, like instant DDL, could speed up MyRocks schema changes, but we needed to be on the 8.0 codebase to use it. Given the benefits of the code update, we decided to migrate to 8.0. We’re sharing how we tackled our 8.0 migration project — and some of the surprises we discovered in the process. When we initially scoped out the project, it was clear that moving to 8.0 would be even more difficult than migrating to 5.6 or MyRocks.

• At the time, our customized 5.6 branch had over 1,700 code patches to port to 8.0. As we were porting those changes, new Facebook MySQL features and fixes were added to the 5.6 codebase that moved the goalpost further away.
• We have many MySQL servers running in production, serving a large number of disparate applications. We also have extensive software infrastructure for managing MySQL instances. These applications perform operations like gathering statistics and managing server backups.
• Upgrading from 5.6 to 8.0 skipped over 5.7 entirely. APIs that were active in 5.6 would have been deprecated in 5.7 and possibly removed in 8.0, requiring us to update any application using the now-removed APIs.
• A number of Facebook features were not forward-compatible with similar ones in 8.0 and required a deprecation and migration path forward.
• MyRocks enhancements were needed to run in 8.0, including native partitioning and crash recovery.

Code patches

We first set up the 8.0 branch for building and testing in our development environments. We then began the long journey to port the patches from our 5.6 branch. There were more than 1,700 patches when we started, but we were able to organize them into a few major categories. Most of our custom code had good comments and descriptions so we could easily determine whether it was still needed by the applications or if it could be dropped. Features that were enabled by special keywords or unique variable names also made it easy to determine relevance because we could search through our application codebases to find their use cases. A few patches were very obscure and required detective work — digging through old design documents, posts, and/or code review comments — to understand their history.

We sorted each patch into one of four buckets:

1. Drop: Features that were no longer used, or had equivalent functionality in 8.0, did not need to be ported.
2. Build/Client: Non-server features that supported our build environment and modified MySQL tools like mysqlbinlog, or added functionality like the async client API, were ported.
3. Non-MyRocks Server: Features in the mysqld server that were not related to our MyRocks storage engine were ported.
4. MyRocks Server: Features that supported the MyRocks storage engine were ported.

We tracked the status and relevant historical information of each patch using spreadsheets, and recorded our reasoning when dropping a patch. Multiple patches that updated the same feature were grouped together for porting. Patches ported and committed to the 8.0 branch were annotated with the 5.6 commit information. Discrepancies on porting status would inevitably arise due to the large number of patches we needed to sift through and these notes helped us resolve them.

Each of the client and server categories naturally became a software release milestone. With all client-related changes ported, we were able to update our client tooling and connector code to 8.0. Once all of the non-MyRocks server features were ported, we were able to deploy 8.0 mysqld for InnoDB servers. Finishing up the MyRocks server features enabled us to update MyRocks installations.

Some of the most complex features required significant changes for 8.0, and a few areas had major compatibility problems. For example, upstream 8.0 binlog event formats were incompatible with some of our custom 5.6 modifications. Error codes used by Facebook 5.6 features conflicted with those assigned to new features by upstream 8.0. We ultimately needed to patch our 5.6 server to be forward-compatible with 8.0.

It took a couple of years to complete porting all of these features. By the time we got to the end, we had evaluated more than 2,300 patches and ported 1,500 of those to 8.0.

The migration path

We group together multiple mysqld instances into a single MySQL replica set. Each instance in a replica set contains the same data but is geographically distributed to a different data center to provide data availability and failover support. Each replica set has one primary instance. The remaining instances are all secondaries. The primary handles all write traffic and replicates the data asynchronously to all secondaries.

We started with replica sets consisting of 5.6 primary/5.6 secondaries and the end goal was replica sets with 8.0 primary/8.0 secondaries. We followed a plan similar to the UDB MyRocks migration plan.

1. For each replica set, create and add 8.0 secondaries via a logical copy using mysqldump. These secondaries do not serve any application read traffic.
2. Enable read traffic on the 8.0 secondaries.
3. Allow the 8.0 instance to be promoted to primary.
4. Disable the 5.6 instances for read traffic.
5. Remove all the 5.6 instances.

Each replica set could transition through each of the steps above independently and stay on a step as long as needed. We separated replica sets into much smaller groups, which we shepherded through each transition. If we found problems, we could rollback to the previous step. In some cases, replica sets were able to reach the last step before others started.

To automate the transition of a large number of replica sets, we needed to build new software infrastructure. We could group replica sets together and move them through each stage by simply changing a line in a configuration file. Any replica set that encountered problems could then be individually rolled back.

Row-based replication

As part of the 8.0 migration effort, we decided to standardize on using row-based replication (RBR). Some 8.0 features required RBR, and it simplified our MyRocks porting efforts. While most of our MySQL replica sets were already using RBR, those still running statement-based replication (SBR) could not be easily converted. These replica sets usually had tables without any high cardinality keys. Switching completely to RBR had been a goal, but the long tail of work needed to add primary keys was often prioritized lower than other projects.

Hence, we made RBR a requirement for 8.0. After evaluating and adding primary keys to every table, we switched over the last SBR replica set this year. Using RBR also gave us an alternative solution for resolving an application issue that we encountered when we moved some replica sets to 8.0 primaries, which will be discussed later.

Automation validation

Most of the 8.0 migration process involved testing and verifying the mysqld server with our automation infrastructure and application queries.

As our MySQL fleet grew, so did the automation infrastructure we use to manage the servers. In order to ensure all of our MySQL automation was compatible with the 8.0 version, we invested in building a test environment, which leveraged test replica sets with virtual machines to verify the behaviors. We wrote integration tests to canary each piece of automation to run on both the 5.6 version and the 8.0 version and verified their correctness. We found several bugs and behavior differences as we went through this exercise.

As each piece of MySQL infrastructure was validated against our 8.0 server, we found and fixed (or worked around) a number of interesting issues:

1. Software that parsed text output from error log, mysqldump output, or server show commands easily broke. Slight changes in the server output often revealed bugs in a tool’s parsing logic.
2. The 8.0’s default utf8mb4 collation settings resulted in collation mismatches between our 5.6 and 8.0 instances. 8.0 tables may use the new utf8mb4_0900 collations even for create statements generated by 5.6’s show create table because the 5.6 schemas using utf8mb4_general_ci do not explicitly specify collation. These table differences often caused problems with replication and schema verification tools.
3. The error codes for certain replication failures changed and we had to fix our automation to handle them correctly.
4. The 8.0 version’s data dictionary obsoleted table .frm files, but some of our automation used them to detect table schema modifications.
5. We had to update our automation to support the dynamic privs introduced in 8.0.

Application validation

We wanted the transition for applications to be as transparent as possible, but some application queries hit performance regressions or would fail on 8.0.

For the MyRocks migration, we built a MySQL shadow testing framework that captured production traffic and replayed them to test instances. For each application workload, we constructed test instances on 8.0 and replayed shadow traffic queries to them. We captured and logged the errors returning from the 8.0 server and found some interesting problems. Unfortunately, not all of these problems were found during testing. For example, the transaction deadlock was discovered by applications during the migration. We were able to roll back these applications to 5.6 temporarily while we researched different solutions.

• New reserved keywords were introduced in 8.0 and a few, such as groups and rank, conflicted with popular table column names and aliases used in application queries. These queries did not escape the names via backquotes, leading to parsing errors. Applications using software libraries that automatically escaped the column names in queries did not hit these issues, but not all applications used them. Fixing the problem was simple, but it took time to track down application owners and codebases generating these queries.
• A few REGEXP incompatibilities were also found between 5.6 and 8.0.
• A few applications hit repeatable-read transaction deadlocks involving insert … on duplicate key queries on InnoDB. 5.6 had a bug which was corrected in 8.0, but the fix increased the likelihood of transaction deadlocks. After analyzing our queries, we were able to resolve them by lowering the isolation level. This option was available to us since we had made the switch to row-based replication.
• Our custom 5.6 Document Store and JSON functions were not compatible with 8.0’s. Applications using Document Store needed to convert the document type to text for the migration. For the JSON functions, we added 5.6-compatible versions to the 8.0 server so that applications could migrate to the 8.0 API at a later time.

Our query and performance testing of the 8.0 server uncovered a few problems that needed to be addressed almost immediately.

• We found new mutex contention hotspots around the ACL cache. When a large number of connections were opened simultaneously, they could all block on checking ACLs.
• Similar contention was found with binlog index access when many binlog files are present and high binlog write rates rotate files frequently.
• Several queries involving temp tables were broken. The queries would return unexpected errors or take so long to run that they would time out.

Memory usage compared with 5.6 had increased, especially for our MyRocks instances, because InnoDB in 8.0 must be loaded. The default performance_schema settings enabled all instruments and consumed significant memory. We limited the memory usage by only enabling a small number of instruments and making code changes to disable tables that could not be manually turned off. However, not all the increased memory was being allocated by performance_schema. We needed to examine and modify various InnoDB internal data structures to reduce the memory footprint further. This effort brought 8.0’s memory usage down to acceptable levels. 

What’s next

The 8.0 migration has taken a few years so far. We have converted many of our InnoDB replica sets to running entirely on 8.0. Most of the remaining ones are at various stages along the migration path. Now that most of our custom features have been ported to 8.0, updating to Oracle’s minor releases has been comparatively easier and we plan to keep pace with the latest versions.

Skipping a major version like 5.7 introduced problems, which our migration needed to solve.

First, we could not upgrade servers in place and needed to use logical dump and restore to build a new server. However, for very large mysqld instances, this can take many days on a live production server and this fragile process will likely be interrupted before it can complete. For these large instances, we had to modify our backup and restore systems to handle the rebuild.

Second, it is much harder to detect API changes because 5.7 could have provided deprecation warnings to our application clients to fix potential issues. Instead, we needed to run additional shadow tests to find failures before we could migrate the production workloads. Using mysql client software that automatically escaped schema object names helps reduce the number of compatibility issues.

Supporting two major versions within a replica set is hard. Once a replica set promotes its primary to be an 8.0 instance, it is best to disable and remove the 5.6 ones as soon as possible. Application users tend to discover new features that are supported only by 8.0, like utf8mb4_0900 collations, and using these can break the replication stream between 8.0 and 5.6 instances.

Despite all the hurdles in our migration path, we have already seen the benefits of running 8.0. Some applications have opted for early conversion to 8.0 to utilize features like Document Store and improved datetime support. We have been considering how to support storage engine features like Instant DDL on MyRocks. Overall, the new version greatly expands on what we can do with MySQL @ Facebook.

The post Migrating Facebook to MySQL 8.0 appeared first on Facebook Engineering.

Planet MySQL

https://theawesomer.com/photos/2021/07/power_generating_magnetic_flywheel_t.jpg

Link

Aerospace engineer Tom Stanton has a thing for flywheels. Here, he first shows us how to build a flywheel that spins smoothly thanks to magnetic levitation, then how that spinning action can be used to generate a small amount of electricity and capture it via copper induction coils.

The Awesomer

https://i.kinja-img.com/gawker-media/image/upload/c_fill,f_auto,fl_progressive,g_center,h_675,pg_1,q_80,w_1200/4394cd19b73d0ab93262913c12e071f3.jpg

Gizmodo

Let’s expand upon the code we wrote in the previous video and clean it up using custom…Laracasts

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There’s one in every crowd. A deranged SJW interrupts Steven during a civil Change My Mind. Watch what happens next.

Steven VS. Deranged SJW! | Louder With Crowder

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http://img.youtube.com/vi/n2WOag1G7Zg/0.jpgA demo project to show how Import works with Laravel Excel, and how to handle relationships rows.Laravel News Links