I had a problem with a Django project that took forever to run its unit tests. The test database took an enormous amount of time to run, upwards of ten to fifteen minutes each. I didn't have a lot of ways around this, because I had to use a base Model that pulled in lots of cascading requirements and I couldn't avoid the dozens of applications it needed to build tables for. This was really hindering my ability to develop, as I rely heavily on constantly running tests in my own pathetic attempt at Continuous Integration.
service postgresql stop
mount -t tmpfs -o size=500m tmpfs /mnt/pg_data_mem/
cp -R /var/lib/postgresql/8.4/main/ /mnt/pg_data_mem/
mount --bind /var/lib/postgresql/8.4/main/pg_xlog /mnt/pg_data_mem/main/pg_xlog
chown -R postgres:postgres /mnt/pg_data_mem/
sudo -u postgres /usr/lib/postgresql/8.4/bin/pg_resetxlog -f /mnt/pg_data_mem/main/service postgresql start
I also set
data_directory = '/mnt/pg_data_mem/main'in postgresql.conf.
This works in development, where I don't need my DB to persist between reboots. If I did want to keep it around, I could just copy from /mnt/pg_data_mem/main/ to /var/lib/postgresql/8.4/main/ and keep it on disc. For now, my one-way solution works.