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As you might know, mysqldump is single-threaded and STDOUT is its default output. As MyDumper is multithreaded, it has to write on different files. Since version 0.11.3 was released in Nov 2021, we have the possibility to stream our backup in MyDumper. We thought for several months until we decided what was the simplest way to implement it and we also had to add support for compression. So, after fixing several bugs, and we now consider it is stable enough, we can explain how it works.

How Can You Stream if MyDumper is Multithreaded?

Receiving a stream is not a problem for myloader, it receives a file at a time and sends it to a thread to process it. However, each worker thread in mydumper is connected to the database, and as soon as it reads data, it should be sent to the stream, which might cause collisions with other worker threads that are reading data from the database. In order to avoid this issue, we ended up with the simplest solution: mydumper is going to take a backup and store it in the local file system that you configured, and the filename will be enqueued to be processed by the Stream Thread which pops one file at a time and pipes to stdout. We study the alternative to send chunks of the file while it is being dumped, but the way that we implemented is simpler and improves the overall performance.

Implementation Details

Here is a high-level diagram of how we implemented it:

When a mydumper Worker Thread processes a job, it connects to the database and stores the output into a file. That didn’t change, but with stream, we are pushing the filename into the mydumper stream_queue.

The mydumper Stream Thread is popping filenames from the mydumper stream_queue, it is going to send the header of the file to stdout and then open the file and send its content.

Then, myloader Stream Thread is going to receive and detect the header, it will create the new file with the filename from the header and store the content in it.

After closing the file, it will enqueue the filename in the myloader stream_queue. A myloader Worker Thread is going to take that file and process it according to the kind of file it is.

By default, the files are deleted, but if you want to keep them, you can use the –no-delete option. 

The header is simply adding — to the filename so you can use myloader or mysql client to import your database. Here is an example:

-- sbtest-schema-create.sql
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `sbtest` /*!40100 DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci */ /*!80016 DEFAULT ENCRYPTION='N' */;

-- sbtest.sbtest1-schema.sql
/*!40101 SET NAMES binary*/;
/*!40014 SET FOREIGN_KEY_CHECKS=0*/;

/*!40103 SET TIME_ZONE='+00:00' */;
CREATE TABLE `sbtest1` (
  `id` int NOT NULL AUTO_INCREMENT,
  `k` int NOT NULL DEFAULT '0',
  `c` char(120) NOT NULL DEFAULT '',
  `pad` char(60) NOT NULL DEFAULT '',
  `pad2` char(60) NOT NULL DEFAULT '',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=100010 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

-- sbtest.sbtest1.00000.sql
/*!40101 SET NAMES binary*/;
/*!40014 SET FOREIGN_KEY_CHECKS=0*/;
/*!40103 SET TIME_ZONE='+00:00' */;
INSERT INTO `sbtest1` VALUES(1,49929,"83868641912-28773972837-60736120486-75162659906-27563526494-20381887404-41576422241-93426793964-56405065102-33518432330","67847967377-48000963322-62604785301-91415491898-96926520291","")
…

Simple Use Cases

A thread writes to a single file to avoid a collision, which improves the performance. However, having thousands of files for a backup of a couple of tables is not manageable. So, the simplest use case is to send everything to a single file:

mydumper -B <SCHEMA_NAME> -h <FROM> > filename.sql

Then you can just simply import it using:

myloader --stream -o -h <TO_SERVER> < filename.sql

Now that you can pipe from a mydumper process to myloader, this execution is possible:

mydumper -B <SCHEMA_NAME> -h <FROM> | myloader --stream -o -h <TO>

Or you can send the stream through the network using nc: 

mydumper -B <SCHEMA_NAME> -h <FROM_SERVER> | nc <MYDUMPER_SERVER> <ANY_PORT>
nc -l <MYDUMPER_SERVER> <ANY_PORT> | myloader --stream -o -h <TO_SERVER>

 

This implementation is using the backup directory on mydumper and myloader as Buffers, you must take this into account, as by default it is going to create a directory where you run it.

Another thing that you need to take into account is that mydumper and myloader will be writing on disk, the whole backup will be written on both File Systems while it is being processed, and use a file system with enough disk space.

Finally, you can keep myloader running and send several mydumper backups. First, you need to run:

nc -k -l <MYDUMPER_SERVER> <ANY_PORT> | myloader --stream -o -h <TO_SERVER>

And then execute:

mydumper -B <SCHEMA_NAME_1> -h <FROM_SERVER> | nc <MYDUMPER_SERVER> <ANY_PORT>
mydumper -B <SCHEMA_NAME_2> -h <FROM_SERVER> | nc <MYDUMPER_SERVER> <ANY_PORT>
mydumper -B <SCHEMA_NAME_3> -h <FROM_SERVER> | nc <MYDUMPER_SERVER> <ANY_PORT>
mydumper -B <SCHEMA_NAME_4> -h <FROM_SERVER> | nc -N <MYDUMPER_SERVER> <ANY_PORT>

Some versions of nc have these two options:

      -k      When a connection is completed, listen for another one.  Requires -l.

     -N      shutdown(2) the network socket after EOF on the input.  Some servers require this to finish their work.

This is very useful if you are refreshing some testing environment and you only need a couple of tables on different databases or if you are using a where clause that only applies to some tables.

Considerations

Usually, when you send data to STDOUT, you are not going to have trouble with disk space usage on the dumper server. That is NOT true if you are using MyDumper. Files will be stored on the mydumper server until they are transferred to the receiving server. For instance, if you have a 10TB database, with a very low network bandwidth compared to the disk bandwidth, you might end up filling up the disk where you keep the files temporarily.

Conclusion

We focus the implementation to speed up export and import processes. Opposite to other software or implementations, we use the file system as a buffer causing a higher disk utilization.

Percona Database Performance Blog

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Today, the book I would like to recommend is Efficient MySQL Performance – Best Practices and Techniques, Daniel Nichter, O’Reilly, 2021.

I participated (just a bit) in the writing of this book as technical reviewer with Vadim and Fipar. I really enjoyed that role of carefully reading the early drafts of the chapters Daniel was writing.

Although Daniel says the book is not for the experts, I think even experts will enjoy it because several key InnoDB concepts are also covered. You can see that I refer to the book often in my A graph a day, keeps the doctor away ! series on monitoring and trending.

If you’re looking for information on transaction isolation and undo logs, fuzzy checkpointing, etc… you’ll find valuable information in the book.

The book is also enhanced with detailed illustrations that help in understanding complicated concepts (InnoDB page flushing, page 216, Source to Replica , page 235, MVCC and undo logs, page 277 are some examples).

Personally, I use this book as I used the 2nd and 3rd editions of High Performance MySQL.

From the beginning to the end of the book, Daniel focuses on the most important and measurable metric for all database consumers: query response time.

I had the chance to meet again Daniel at Percona Live and offered me a signed copy 😉

I also had the privilege of having my review published in the back of the book:

If you are looking for a book to improve your knowledge of MySQL or if you are a software engineer who needs to deal with MySQL, this is a good choice.

I also recommend reading Daniel’s blog which is a complement to the book.

Have a good read and enjoy MySQL!

Planet MySQL

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Gizmodo

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Home defense is a hot topic in the firearms community, with newbies and seasoned pros debating the merits of different platforms.

But what should you consider when setting up a home defense or bedside gun?

Well, I’m here to help. I’m going to try and dial in on some suggestions of things I would consider essential in home defense, as well as looking at the stats behind home invasions.

I will preface this by saying that everything contained in this article is meant as a general picture and in no way should be construed as an all-inclusive, gospel, or a cookie-cutter response to fit every person or scenario.

There are simply too many variables to account for in one article in dealing with a home defense scenario and what the correct tool for the job is.

But I’ve done my best to offer a broad perspective that should at least get you started. So keep reading to learn more!

Science of Home Defense

One of the common misconceptions in the firearms community is that we must prepare to fight off waves of invaders in a home defense situation.

Could that happen? Sure. Is it likely? Reading through recent home invasion stories reported to the police, no.

Local statistics in Las Vegas are that the likelihood is one or two (average was 1.5) persons will attempt to gain entry, though more are possibly outside in supporting roles.

This can vary from area to area, but lower-income locations typically see more burglaries and attempts.

Per the FBI’s Criminal Justice Information Services Division, a break-in occurs once every 26 seconds in the United States.

Of those break-ins, 61% of offenders were unarmed at the time of the offense, and only 12% of all violent break-ins involved the offender having a firearm. Often, the offenders were known to the victims, and an assault occurred in only 5% of the break-ins reported.

So, what does all that have to do with setting up your home defense? First and foremost, the best deterrent you can have to prevent a home invasion is a security system — 83% of would-be burglars check for some sort of security system before breaking in.

If you choose to defend yourself, your home, and your family with a firearm, you need to understand that you may know the person attempting to break in, they may or may not be armed, and that the likelihood is that they want to get in and get out with cash or goods, not hurt you.

In short, make sure you understand your local laws VERY well.

What’s the Best Home Defense Tool?

This is a very complicated answer, and there isn’t a blanket “this works best for everyone” response.

Instead of going into a nuanced answer, I’m going to attempt to give some information that will highlight the strengths and weaknesses of different firearms for home defense.

Ultimately you will have to decide what will work best based on your level of familiarity and comfort with a particular platform, the layout of your house, availability of defensive ammo, and many other variables.

Why does the layout of your house matter? Defending a one-bedroom apartment will be a vastly different scenario than trying to defend a 10,000-square-foot ranch house on 27 acres of land.

The key here is realizing that you are legally responsible for everything a bullet does once it exits the muzzle of your firearm after being discharged.

Sending a round through a wall into your neighboring townhouse means you are responsible for any damages or injuries it causes. Different tools will excel in different environments, so figure out what will do the best for you.

Investing in some deterrents can often prevent the need to use force.

We already saw that potential burglars check for a security system, so that is the first thing you should be investing in. (Or take a look at our article on the Best Ways to Secure Your Home for more tips!)

Beyond that, what’s the next step to deterring a burglary without escalating to force? A good-quality handheld flashlight and properly using it.

Let’s face facts; if something goes bump in the night, most of the time, there isn’t a need to point a gun at it.

The use of a flashlight to investigate what is skulking around your property allows you to make an informed decision on whether the use of force is necessary or if you simply caught your teenage kid sneaking back into the house.

If you spot a would-be burglar, the threat of being caught and detained statistically shows they are less likely to stay.

In that 5% of break-ins that turn into an assault, however, use of force may be needed, and that is where other tools are more suitable for the job.

Hands & Home Defense

I’m not getting into a debate over semi-automatic vs. revolver or a debate on which caliber is the best.

The correct answer is finding a gun that you will train to become more proficient with, that can add the features you work best with, and ensure you are confident in its use.

I will not recommend a .22 LR as a defensive handgun, but if that is all you have, you better make it work for you.

Generally, any caliber from .380 and up that offers hollow-point rounds can be suitable for a defensive gun. Each caliber will have some advantages and disadvantages.

Quality matters for defensive guns. Right now, finding quality guns can be both difficult and expensive, but you have to ask yourself what your life is worth.

Stick to brands with proven track records of success and quality like Glock, CZ, H&K, Smith & Wesson, Sig Sauer, FN, etc.

Set your gun up for dominance and success.

Let’s face it, in the middle of the night; you should have the advantage in your home over a stranger. You know the layout better, you know where obstacles typically are, and you are just generally more familiar. Why not press that advantage with your firearm?

If you find yourself in a dark house trying to defend yourself, getting positive target identification and getting sights on target are the two things with which you need to be concerned — speaking in terms of operating the gun itself, not considering things like finding and using cover, etc.

To this end, I do recommend a weapon-mounted light of good quality — Streamlight, Surefire, Modlite, etc.

Additionally, I am a huge advocate for adding an optic to your pistol. Optics allow you to be threat-focused, rather than requiring you to switch to sight focus beyond a certain distance.

Optics allow you to acquire your aiming device regardless of lighting conditions and permit faster follow-up shots with more consistency, regardless of shooting experience.

Can’t night sights/fiber optic sights do the same thing? Yes and no. They will allow you to find your sights faster, but you are still limited by lighting conditions to get sights on target, and iron sights still require sight focus vs. being target focused.

The last component is ammo. Find good quality, consistent hollow points that will get the job done.

Examples of this would include but are not limited to Speer Gold Dot, Hornady Critical Duty, or Federal HST for larger handguns like the Glock G17 and G19.

For shorter barreled guns like Glock G43x, S&W Shield, or Sig P365, Hornady Critical Defense or Federal Punch are better options.

Speaking with Chuck Haggard of Agile/Training & Consulting, he mentioned that shorter barreled handguns lead to the round not fully expanding on some of the duty grade hollow points.

His testing and experience showed that Critical Defense was a much better choice in that scenario.

Make sure your gun is rated for any +P or +P+ ammo you intend to shoot, and then shoot a magazine worth through your gun to make sure it cycles without any issue.

Pistols do have their limits, and you need to know them.

Depending on the handgun you’ve selected, you will have between six and 17 rounds to use for your defense without reloading.

Looking back at the average number of attackers, that is between three and eight shots at each adversary.

Add in adrenaline and the high stress of the situation, and you now have a scenario where you are likely reverting to your lowest proficiency and training to put hits on target.

Rifles for Home Defense

Many, myself included, choose to use a rifle or pistol version of a rifle for home defense.

Rifles offer a more stable, more forgiving firing platform than handguns due to the increased points of body contact with the gun.

Additionally, they typically offer more ammunition to feed and, in most cases, provide increased velocity over handguns.

So, when will a rifle be an advantage over a handgun? If your house is laid out in such a manner that you can create distance, a rifle is going to generally be better than a handgun.

I want to clarify this in that shot placement matters; either way, people can generally fire a rifle better than a handgun at low skill levels. At 15 to 20 yards, both can be effective; it will come down to training and comfort.

In my case, my entire family is housed on the second floor of our home. I can then use a rifle to defend against people coming upstairs and know that it will be effective.

Much like handguns, some definite upgrades are recommended.

Just like with handguns, a rifle will benefit from a weapon-mounted light. Target identification is still a priority, even more so at greater distances.

Some form of quality optic is needed as well. I prefer red dots that I can leave on like an Aimpoint CompM5 or T2 so that my gun is ready when I pick it up. I know others that run low-power variable scopes and are very effective.

I would avoid using just iron sights, as you still suffer the same limitations as handgun sights. Invest in a quality optic, stay away from knocks-offs and low-quality products, and prosper.

Lastly, a sling is a must-have for a defensive rifle. This allows the user to retain possession of the weapon if hand to hand occurs and allows for retention of the rifle if you need your hands free to pick something or someone up to help.

Rifles are not without their drawbacks, though. That sling that I just mentioned means that the gun is attached to you to some extent. A knowledgeable attacker can use that as leverage against you to control your body and/or throw you.

In closer quarters or houses with lots of turns, a longer barrel can be a hindrance in terms of maneuverability.

Ammo selection, along with good shot placement, also plays a huge role in the effectiveness of a rifle. Once again, something like Speer Gold Dot, Federal LE Tactical, or Hornady TAP FDP that are made to have a hollow or soft point allow for better defensive use than a full metal jacket round.  

TAP and other fragmenting rounds are especially worth considering if over-penetration is a concern in smaller living spaces. Please understand that fragmenting rounds are different than frangible rounds, and under no circumstances are frangible rounds a go-to for personal protection.

Going back to our average number of people in the break-in, rifles offer more rounds to put on target.

An AR-15 magazine comes in 10-round, 20-round, and 30-round magazines as the most common options. You can get larger capacity drum magazines, but many tend to be lower quality, finicky, and not reliable to consider for a self-defense scenario.

As I mentioned above, it may take more than one round to stop someone from attacking you, so having more ammunition to expend in that pursuit is a good thing.

Shotgun Setups for Home Defense

Shotguns for home defense use have become a more heated topic in the last few years.

Search any gun forum or message board, and you’ll encounter people saying…shotguns are the best defensive gun ever, you just need to rack the action to scare away every bad guy in a 3-mile radius, you don’t have to aim, etc.

The truth is that shotguns have their place in home defense, but like anything else, they aren’t a blanket answer to a problem. Sometimes shotguns will be the optimal choice and other times they won’t.

The first thing to consider is the gun itself…

Remington 870s or Mossberg 590s are the go-to pump-action shotguns.

If semi-automatic shotguns are more your thing, the Beretta 1301, Benelli M2 or M4, and the Mossberg 940 will do.

Once you have a good-quality, reliable shotgun, the next step is patterning your ammo.

This involves getting the ammo you intend to use and shooting it at various distances to see how the pellets spread and pattern on a target. 

This is important, as using different types of buckshot with different guns will get you different results. As you are responsible for everything your ammo does after it is fired, you need to know exactly where these pellets will fly, where they end up, and if you will face any unintended damage.

There are two viable shotgun rounds for defense, buckshot, and slugs. Birdshot and snakeshot are not suitable for self-defense, and their use could leave you facing an angry opponent that is still able to function.

Buckshot utilizes larger pellets that are ideally suited for home defense, but not all of them pattern the same. Depending on your barrel and if you are running a choke or not, Federal Flight Control may be an option, and generally, 8-pellet buckshot is going to be superior to 9-pellet.

Slugs are your other option for self-defense. Slugs utilize a solid projectile instead of pellets and were originally designed for use on larger game.

Think of firing a softball instead of marbles. Slugs will be a better choice for defensive rounds at longer distances, as buckshot patterns will spread out more there. Inside of 10 yards, though, buckshot will be better.

Distance is generally going to be the enemy of a shotgun beyond 30 yards or so. Inside of that range, a shotgun is a devastating tool that will very quickly end engagements.

Contrary to popular myth, you still have to aim a shotgun for it to be effective. To that end, a good quality light for target identification is worth considering. As with other platforms, mounting an optic is not a bad idea.

Additionally, a sling is a great idea for the same reason discussed earlier. Also, keep in mind that a shotgun will generally be longer and often heavier than an AR-15 or AK-47.

Shotguns do have their drawbacks, though. Like rifles, movement and mobility can be hindered by the size of the gun.

Additionally, recoil mitigation for follow-up shots is something that must be trained, as some people will find the gun awkward and uncomfortable without adjustments made.

Reloading a shotgun is also a bit more involved than slapping a fresh magazine in, so it is a skill that must be trained to be fast and proficient at it.

Applying shotguns to our two-attacker scenario, this is where things are very different.

Depending on which shotgun model you have, the tube may hold between six and eight rounds without extended tubes.

While this leaves only three or four rounds per assailant within a shotgun’s effective range, one round delivered to an attacker is devastating. The shot must still hit, but if it does, there is a very high probability that the fight is now over and your opponent’s behavior has changed.

Final Thoughts

No two scenarios are the same, and thus no answer will fit universally. Find the self-defense setup that makes sense for you, train with the tools and understand the tactics needed to win the fight.

Also, source out quality information, and do not be afraid to challenge the misconceptions you might have or might have heard.

In the end, defending yourself and those you care about is the only thing that matters, so give yourself as much advantage as possible.

The post Set Up Your Home Defense Gun: Rifle, Shotgun & Pistol [GUIDE] appeared first on Pew Pew Tactical.

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A critical skill for any rifle shooter, mounting your own scope will save you time, money, and teach a core skill for long range shooting.Recoil

There are two types of IFs in MySQL: the IF statement and the IF function. Both are different from each other.  In this article, we will explain their diversities and show usage examples. Also, we will review other MySQL functions. Contents MySQL IF statements MySQL IF-THEN statement MySQL IF-THEN-ELSE statement MySQL IF-THEN-ELSEIF-ELSE statement Examples of […]

The post MySQL IF – Function and Statement (with Examples) appeared first on Devart Blog.

Planet MySQL

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With all the recent talk about removing guns from the hands of law-abiding citizens, I think it’s a good time to revisit this video from back in 2019.

Not the Bee