General – Page 2 – Tony Showoff

Better Unicode support for MySQL (including emoji)

When it comes to character support I think the only thing that should ever be used is Unicode. That's right, I said it. However, when it comes to support in MySQL, things get a little bit murky.

I never had too much of an issue using plain ol' utf8_general_ci, however when trying to add language support for Gothic (tested because it's rare), I ran into a serious issue:

Incorrect string value: '\xF0\x90\x8C\xB0\xF0\x90...'

Son of a …

This issue is caused by the fact UTF-8 in MySQL isn't fully supported by utf8 the character set, it only supports a maximum of 3-byte characters. If you want something more realistic you're going to need to have at least MySQL 5.5.3 and you're going to have to use utf8mb4 not regular utf8. Yes, seriously.

Make sure you read through all this before trying anything, because there are edge issues, especially with indices (indexes) which you may need to consider.

Also back up your data first.

Updating Database

I'll be working under the assumption that you want your entire database to be utf8mb4, but if you don't then you'll have to adjust a bit, but seriously reconsider joining the 21st century if you're not using unicode. I'm also assuming you want case insensitive text, and if you don't, replace utf8mb4_unicode_ci with utf8mb4_bin — most people want case insensitive text in most cases.

Update the default character set and collation for your database:

ALTER DATABASE `mydatabase` CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Updating Tables

First we need to change the default character set, this way when you add new columns in the future, or whatever, you don't need to worry about adding all of the character set specification:

ALTER TABLE `mytable1` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Updating Table Columns

Now, you can convert one column at a time, and this may be what you wish to do if you require different character sets for your CHAR, VARCHAR, and TEXT columns, here's how you do that:

ALTER TABLE `mytable1` CHANGE `mycolumn` `mycolumn` VARCHAR(64) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT  '';

Now obviously you're going to want to make sure that you're converting to the same column type and length, etc, the above is for example only and if you copy/paste it, you may screw up your column schema. Essentially you're just using ALTER TABLE CHANGE on the column in order to change the character set to utf8mb4 and collation to utf8mb4_unicode_ci.

If on the other hand you just want to change the entire the entire table at once, you can do:

ALTER TABLE `mytable1` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Updating Table Indices

When changing the character type, you may run into this on InnoDB:

ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes

or this on MyISAM:

ERROR 1071 (42000): Specified key was too long; max key length is 1000 bytes

Ah, CRAP!

Oh snippy snap, snap, there are solutions:

If you're using InnoDB on MySQL 5.6.3 or higher you can enable innodb_large_prefix in your MySQL config file (more information in manual here), but if you aren't you can take a few steps to work it out the old way:

Make note of the conflicting index, it's going to likely be one which is something like VARCHAR(255) or an index across multiple columns which includes VARCHAR. Make note of the index name, type, and which column(s) it crosses.
In my own scenario, I had a lot of columns which included some sort of VARCHAR(254) and ID which was binary(20). Now it seems like 254+20 = 274, and hey that's less than 767 (or 1000) so what's the deal?Well, not so fast there, Professor.MySQL doesn't count literal bytes in VARCHAR when it comes to Unicode, rather potential Unicode bytes are themselves counted as a byte (wait, what?).So if the column is 254 and it's utf8 that means the actual potential length is literally (254 * 3) bytes, and with utf8mb4 it's (254 * 4). So really the length of the key you're trying to create is ((254 * 4) + 20).InnoDB only allows a maximum of 255 bytes for the column in an index with utf8 and 191 bytes for utf8mb4.So if you need the entire column indexed, you aren't going to want to change the character set for that column(s), and instead I recommend changing all others one by one (as seen in the Table Columns section) rather than trying to convert the entire table. However if you do not need the entire column to be index, and in certain cases I did not.Drop the index:
```
ALTER TABLE `mytable1` DROP INDEX `theindex`;
```
Then recreate it with the offending column(s) limited to 191:
```
ALTER TABLE `mytable1` ADD INDEX `theindex` (`mycolumn` (191));
```
or if across multiple columns (assuming mycolumnb is not utf8 for example):
```
ALTER TABLE `mytable1` ADD INDEX `theindex` (`mycolumn` (191),`mycolumnb`);
```

As long as the indices are the same, and in the same column order, you should receive the same benefits for the indices without worrying about redoing your queries.

Additional Notes and Considerations

If a column is not being used for search and case insensitivity isn't an issue, instead of using CHAR or VARCHAR, I suggest using BINARY and VARBINARY. Not only is comparison vastly faster, but also there's less to worry about as far as character set issues go, i.e. they don't matter. Further also VARBINARY is literal length so the UTF-8 limitations described in the index section of this post do not apply, so you can get the full width for your index.

Additionally instead of using TEXT, use BLOB, for the same reasons, but also realise the same limitations apply, such as no fulltext searching.

In summation, if you don't need case sensitivity and you don't need fulltext search, consider BINARY, VARBINARY, and BLOB over CHAR, VARCHAR, and TEXT, it'll be a lot easier to deal with when it comes to Unicode.

You can learn more about this on my MySQL performance, using case insensitive columns post.

Database Connections

Depending on your programming language, you may need to specify when connecting which chartype to use (you can also, in most cases, specify this on configuration, see that section at the bottom), this usually can be done by sending this query right after connection:

SET NAMES utf8mb4;

Configuration

You can edit your my.cnf (or my.ini on Windows) and make these changes to the appropriate sections of the configuration file (applicable to MySQL 5.6, older versions may need adjusted configuration):

[client]
default-character-set = utf8mb4

[mysql]
default-character-set = utf8mb4

[mysqld]
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci

So, what the hell is type casting anyway?

Casting is a way to take a liquid and mold it int… oh yeah

So casting is just a fancy way to refer to type conversion, that is where you change the "type" of a variable from one thing to another. For example changing a string to an integer.

How about some examples? Is that what you want?

OK, fine, you talked me into it. Here are some PHP examples:

$var = '1000';
var_dump($var); // Returns string(4) "1000"

$var = '1000';
$var = (int)$var; // Here is where we cast it
var_dump($var); // Returns int(1000)

So, who cares? What's the point?

Well, depending on what you're wanting to do, it's important to change the type, and this is especially true in languages where there is no dynamic typing (like C#) and it's still useful in languages with dynamic typing like PHP, because it allows for one to avoid potential issues with mathematics, concatenation, etc. Aside from math related things, in PHP I use (int) a lot to clean up variables for SQL queries for both safety and also so MySQL doesn't have to convert the types itself.

You can learn more about type casting in PHP specifically and why it's a great way to do certain things here: Casting int faster than intval in PHP.

Let them learn COBOL / PHP isn't evil

I received this in my inbox earlier:

What programming languages should a modern-day programmer have in his/her arsenal? (Quora)

OK, fine, now I'm forced to evangelize for PHP, this puts me in a really painful position, but since I'm apparently the only person

reading this who can think for myself instead of freebasing whatever the Valley tells me to use, here we go…

The general theme seems to be to either learn a pretty hardcore language like C or C++ which won't benefit most people right away these days, since there's almost no excuse to make classic applications anymore. I think if anything it will discourage some people from learning to program since they have to spend a lot of time learning to clean up garbage, compiling, debugging, etc. Way to ruin their fun by making them spend all that time on a language better suited for drivers than web or phone apps.

Promoting Java is also a thing for some reason, I thought we were trying to kill this language? It's still used by a lot of places, but so is COBOL. In fact there's still a ton of places that use COBOL, so why not promote it? Probably because it doesn't come with a hipster mustache and a really tall bicycle.

If it's about job security, automatically Python and Ruby were a terrible suggestion, same with Erlang. You might as well be one of those skinny guys promoting Lisp.

A huge one though is promoting Python (and sometimes Ruby), blindly suggesting it's the best way to go without consideration for how huge of a pain in the ass it is to start a project. The syntax of the language(s) is very easy and the language itself quite powerful, but also slower than other options, harder to get going, and not widely supported. Starting a project in Python is about as difficult as starting a car by putting the engine in the car first. Turnkey? Hell no. You can get used to it, take some shortcuts, etc, but really for a new person, it's a nightmare.

It's really a hipster language, and Monty Python isn't funny, I'm just saying, it really isn't, seriously.

That's unrelated to this topic, but since Python is named after it, I felt it was important for me to communicate that it's just … knights who say Ni? yeah, falling over laughing. Monty Python films had a few snicker moments here and there, but it was mostly diarrhea (or diarrheoa). I liked Flying Circus much better, why don't many people talk about that?

Yes, I've seen all of the popular films, and no I didn't laugh. I didn't go into expecting it to be about as funny as a hernia operation either. I had thought they would be funny since that's what people were saying, and after wasting about six hours of my life I realized: holy crow, I didn't laugh once. No, I mean that literally, I didn't laugh one time. A few smiles, sure, but not much else.

Anyway, where was I? Oh yeah, terrible ideas…

Some other promotions for assembly, as if it's 1977 or something.

In general though there was a lot of PHP hate spread through the entire thread, mostly that it was bad, but nobody ever saying why, it just is. That's a lot of bullshit. It's because PHP is widely used, widely available, and despite their claims PHP has made a massive amount of headway over the last few years, and is only getting better.

Much of the complaints about PHP people have are true.. if you've fallen out of a time machine from 2004. Hating PHP is like hating MySQL, it's just easier to ignore the last decade and pretend nothing ever changes, then go on to promote your slower, less widely available, much cooler alternatives of Python and PostgreSQL.

It's just the toxic runoff coming from the Valley of essentially acting like Pookie for anything cool coming out of the Valley, Bay Area, etc. And hey, I've lived in the Bay Area, so that makes me an authority on everything there.

I don't mind the C# suggestion, I don't like the platform limitations. Yeah there's mono, but yeah, who cares. C# has a lot of things like static typing that I wish PHP had, but Hack from Facebook does add a lot of those features right back into PHP and many of those will be moved into core PHP over the next couple of years.

The blinding hatred of PHP out there causes people to promote things in a manner which can slow newcomers down. PHP sure isn't perfect and there are of things I'd change about PHP, but it's faster, extremely powerful, and most importantly easy as hell to get going.

I'm of the mind though if we're going to want to stop people from learning to program, then yes, let's promote Python, Ruby, Erlang (what the heck are you promoting this for, do people making small sites really need message queues? Don't be a jackass.), and while we're at it Java. Languages which can be easy at face value, easy in syntax, but a pain in the ass to get going and deal with, not to mention slower. Except Java and Erlang, those can be pretty fast.

So reasons not to learn PHP?

It's not really cool
It's not the steam punk of languages like Python, so you don't get a stupid ass top hat with non-functioning goggles and proclaim you're awesome
It's making headway faster than most languages, some of which aren't even changing or improving at all any more.
It's widely available, i.e. essentially everywhere, so you're not held hostage by host availability
It will help you learn C-style syntax which you can more easily pass on to other languages like JavaScript (also used on the web), plus countless other languages like C, C++, Java, C#, etc

Python and Ruby aren't bad to have in your arsenal, but blindly suggesting them first, when C-style languages is king is just ridiculous. Meanwhile the most popular web language being PHP, which is a C-style language, oh no, don't use that, it's bad just because it's bad, I mean, no reasons listed here, it just is.

Anyway, now a choice, spend 10 seconds starting a PHP project or spend half an hour setting up a Python environment and prepping things just to get coding, and I mean really coding, throwing things directly to the interpreter isn't how you make real projects, it's how you demonstrate the language without making it obvious how much of a pain it is.

I'll use the language best suited for the situation, I'm not going to blindly dislike something because a broader community of self-deluded permanent man-children hate it.

My choices of languages:

PHP
JavaScript / node.js
Ruby
C#

My choice of languages in 2004:

Perl
C++
PHP

My choice of languages in 1997:

Perl
C++
Visual Basic

Nope, things never change, I'll just use Python forever and tell everyone that's all I've ever loved.

I hope you can appreciate the irony of blind hatred and ignorance of modern PHP meanwhile essentially doing the same thing with Python. That's my point, when it's turned around, it's obvious how idiotic you look.