Migrating Gitlab from MySQL to Postgres

Recently, I migrated Apovedas Gitlab installation from using MySQL as database server to PostgreSQL. Thats because until now, I have used the manual gitlab setup guides, and I now want to change this to use the automatic setup/provided packages, which all use postgres.

Install Postgres and create the database

(Taken from the Gitlab installation manual):

sudo apt-get install -y postgresql postgresql-client libpq-dev

# Login to PostgreSQL
sudo -u postgres psql -d template1

# Create a user for GitLab.
template1=# CREATE USER git;

# Create the GitLab production database & grant all privileges on database
template1=# CREATE DATABASE gitlabhq_production OWNER git;

# Quit the database session
template1=# \q

# Try connecting to the new database with the new user
sudo -u git -H psql -d gitlabhq_production

Install PGloader

git cl https://github.com/dimitri/pgloader.git
apt-get install sbcl libsqlite3-dev make curl
cd pgloader
make pgloader
cd ~

Migrate the database

We need to create a new file containing the commands for pgloader: nano pgloader-commands, and insert the following into it:

LOAD DATABASE
 FROM    mysql://gitlab:<your-mysql-password>@localhost/gitlabhq_production
 INTO    postgresql://git@/gitlabhq_production
 WITH    create tables, create indexes, foreign keys, reset sequences;

Then, run it:

sudo service gitlab stop
sudo -u git pgloader/build/bin/pgloader pgloader-commands
rm pgloader-commands

Change Gitlab config, and restart

cd /home/git/gitlab/config
sudo mv database.yml database.yml.backup
sudo cp database.yml.postgresql database.yml
sudo chown git:git database.yml
sudo chmod 0644 database.yml

# install pg gem
cd /home/git/gitlab
sudo -u git -H bundle install --deployment --without development test mysql aws

# restart gitlab
sudo service gitlab start

# check if app runs, if not, check log
tail -f log/unicorn.stderr.log

Uninstall mysql

sudo apt-get purge mysql-client mysql-common mysql-server

Done! You are now running Postgres.

NumPy and SciPy on OSX

At ETHs D-ITET (Electrical Engineering Departement), you are more or less forced to use Matlab.

As a programmer, Matlab’s organically grown and inconsistent syntax and structure hurts my eyes. Also, one gets accustomed to an extremely expensive, closed commercial product.

Enter NumPy and SciPy: These Python libraries have most of the features needed in 2nd Year of ETH. Also, its very easy to change from Matlab, as most commands are equal or similar.

Guide to install PyLab on OSX

You can now use IPython from the CLI. Also available are a QT (Graphical) console (ipython qtconsole), and browser-based so-called notebooks similar to Mathematicas GUI (ipython notebook).

Here, you find a complete beginners guide.

An Example:

$ ipython --pylab
  Python 2.7.6 (default, Feb 28 2014, 12:18:57)
  Type "copyright", "credits" or "license" for more information.

  IPython 1.2.1 -- An enhanced Interactive Python.
  ?         -> Introduction and overview of IPython's features.
  %quickref -> Quick reference.
  help      -> Python's own help system.
  object?   -> Details about 'object', use 'object??' for extra details.
  Using matplotlib backend: MacOSX

  In [1]: plot(cumsum(random.random_integers(-1, 1, 100)))
  Out[1]: [<matplotlib.lines.Line2D at 0x107c696d0>]

  In [2]:

Which produces the following image:

Random Walk using NumPy and Matplotlib