I love Cockpit CMS

I've had a lot of fun playing with Cockpit CMS.
It's a "An API-driven CMS without forcing you to make compromises in how you implement your site."

Its a CMS without a front end. The front end is completely up to you. This tool takes care of all the back-end stuff. It provides a UI for building content types, uploading media, editing media and content, doing site backups and authentication. How the data is displayed is entierly up to you.

Built with a custom microframework called "Lime" which looks alot like slim2 and a storage system called "Mongo lite", it provides everything you need to build small sites that are a joy to work with.

The documentation includes a walk-through on how to build a simple blog.

Working with Bitfields in MySQL

Problem: You are working with an antique data model where someone thought is was a good idea to store true/false data as bits in an integer value.

Bitfields are a kind of composit column which stores many logical values in one physical column as an integer value. It allows you to store many yes/no options in a very small space. When looking at this data you'll see integers but what is really important is the bits that make up that number.

Lets say I want to store event level info in a log table.

CREATE TABLE eventlog(
level INT(11) NOT NULL,
msg varchar(32) NOT NULL
);

bit 1 (0001) = fatal error (int 1)
bit 2 (0010) = warning (int 2)
bit 3 (0100) = error (int  4)
and bit 4 (1000) = user error (int 8)

What if I have both a user error and a warning error? That's int 6.
Or all options? That's int 15.
Or all the level's with a warning logged? That's int 2,3,7 and 15

Querying or filtering on a single bit is hard. It's as difficult to work with as CSV string columns. If this data had been normalized properly, each part would have its own column in the database.

MySQL has a few built in functions for working with bitfield columns:
Check out EXPORT_SET and MAKE_SET

SELECT
msg,
EXPORT_SET(level,1,0,'',4) AS debugBits,
SUBSTRING(EXPORT_SET(level,1,0,'',4),1,1) AS hasFatal,
SUBSTRING(EXPORT_SET(level,1,0,'',4),2,1) AS hasWarning,
SUBSTRING(EXPORT_SET(level,1,0,'',4),3,1) AS hasError,
SUBSTRING(EXPORT_SET(level,1,0,'',4),4,1) AS hasUserError
FROM eventlog;

which results in:

msg debugBits hasFatal hasWarning hasError hasUserError
test1 0000 0 0 0 0
test2 1010 1 0 1 0
test3 0010 0 0 1 0

We're taking the bitfield column, turning the column into strings and pulling the string apart. Notice here that bit 1 is on the far right.
 

What happens if I want to add context to this data. That's what MAKE_SET is for.

SELECT
msg,
MAKE_SET(level,
'fatal',
'warning',
'error',
'userError') AS levelTextCsv
FROM warnings;

which will output your bitfield value as a single CSV column with text for each selected option.

Bitfields aren't ideal. Combining data into a single column is an anti-pattern in SQL. Should you encounter this in the wild, you'll know what to do.

 

Rename a MySQL database

 

Problem: You need to change the name of a mysql database without reloading it.

MySQL used to contain a "RENAME DATABASE" command but it would occasionally hose the database.

RENAME {DATABASE | SCHEMA} db_name TO new_db_name;

This statement was added in MySQL 5.1.7 but was found to be dangerous and was removed in MySQL 5.1.23. … Use of this statement could result in loss of database contents, which is why it was removed. Do not use RENAME DATABASE in earlier versions in which it is present.

So what should you do instead?

If all your tables are physically located on the same disk, you can use "create db" + "rename table" to move tables between databases without reloading them.

-- ensure the char set and collate match the existing database.
SHOW VARIABLES LIKE 'character_set_database';
SHOW VARIABLES LIKE 'collation_database';


CREATE DATABASE `database2` DEFAULT CHARACTER SET = `utf8` DEFAULT COLLATE = `utf8_general_ci`;
RENAME TABLE `database1`.`table1` TO `database2`.`table1`;
RENAME TABLE `database1`.`table2` TO `database2`.`table2`;
RENAME TABLE `database1`.`table3` TO `database2`.`table3`;

Reference: http://dev.mysql.com/doc/refman/5.7/en/rename-table.html
This answer is also posted on stackoverflow.