This document describes how to get the postgres database ready to use and maintain it (do migrations / changes to the structure).
Note
This is about a stable database, useful for longer development work or production. A super quick way to get a postgres database running with Docker is described in tut_toy_schedule
. In docker-compose
we use both postgres and redis.
We also spend a few words on coding with database transactions in mind.
Table of contents
Notes:
- We use postgres 12 at the moment, but any version starting with 9 probably works.
- We assume
flexmeasures
for your database and username here. You can use anything you like, of course. - The name
flexmeasures_test
for the test database is good to keep this way, as automated tests are looking for that database / user / password.
On Unix:
sudo apt-get install postgresql-12
pip install psycopg2-binary
On Windows:
- Download postgres here: https://www.enterprisedb.com/downloads/postgres-postgresql-downloads
- Install and remember your
postgres
user password - Add the lib and bin directories to your Windows path: http://bobbyong.com/blog/installing-postgresql-on-windoes/
conda install psycopg2
Make sure postgres represents datetimes in UTC timezone ^^^^^^^^^^^^^
(Otherwise, pandas can get confused with daylight saving time.)
Luckily, many web hosters already have timezone= 'UTC'
set correctly by default, but local postgres installations often use timezone='localtime'
.
In any case, check both your local installation and the server, like this:
Find the postgres.conf
file. Mine is at /etc/postgresql/9.6/main/postgresql.conf
. You can also type SHOW config_file;
in a postgres console session (as superuser) to find the config file.
Find the timezone
setting and set it to 'UTC'.
Then restart the postgres server.
service postgresql restart
Setup the "flexmeasures" Unix user ^^^^^^^^^^^^^
This may in fact not be needed:
sudo /usr/sbin/adduser flexmeasures
Create "flexmeasures" and "flexmeasures_test" databases and users ^^^^^^^^^^^^^
From the terminal:
Open a console (use your Windows key and type cmd
). Proceed to create a database as the postgres superuser (using your postgres user password):
sudo -i -u postgres
createdb -U postgres flexmeasures
createdb -U postgres flexmeasures_test
createuser --pwprompt -U postgres flexmeasures # enter your password
createuser --pwprompt -U postgres flexmeasures_test # enter "flexmeasures_test" as password
exit
Or, from within Postgres console:
CREATE USER flexmeasures WITH UNENCRYPTED PASSWORD 'this-is-your-secret-choice';
CREATE DATABASE flexmeasures WITH OWNER = flexmeasures;
CREATE USER flexmeasures_test WITH UNENCRYPTED PASSWORD 'flexmeasures_test';
CREATE DATABASE flexmeasures_test WITH OWNER = flexmeasures_test;
Finally, test if you can log in as the flexmeasures user:
psql -U flexmeasures --password -h 127.0.0.1 -d flexmeasures
\q
To find the nearest sensors, FlexMeasures needs some extra Postgres support. Add the following extensions while logged in as the postgres superuser:
sudo -u postgres psql
\connect flexmeasures
CREATE EXTENSION cube;
CREATE EXTENSION earthdistance;
If you have it, connect to the flexmeasures_test
database and repeat creating these extensions there. Then exit
.
Configure FlexMeasures app for that database ^^^^^^^^^^^^^
Write:
SQLALCHEMY_DATABASE_URI = "postgresql://flexmeasures:<password>@127.0.0.1/flexmeasures"
into the config file you are using, e.g. ~/flexmeasures.cfg
Get structure (and some data) into place ^^^^^^^^^^^^^
You need data to enjoy the benefits of FlexMeasures or to develop features for it. In this section, there are some ways to get started.
Here is a short recipe to import data from a FlexMeasures database (e.g. a demo database) into your local system.
On the to-be-exported database:
flexmeasures db-ops dump
Note
Only the data gets dumped here.
Then, we create the structure in our database anew, based on the data model given by the local codebase:
flexmeasures db-ops reset
Then we import the data dump we made earlier:
flexmeasures db-ops restore <DATABASE DUMP FILENAME>
A potential alembic_version
error should not prevent other data tables from being restored. You can also choose to import a complete db dump into a freshly created database, of course.
Note
To make sure passwords will be decrypted correctly when you authenticate, set the same SECURITY_PASSWORD_SALT value in your config as the one that was in use when the dumped passwords were encrypted!
First, you can get the database structure with:
flexmeasures db upgrade
Note
If you develop code (and might want to make changes to the data model), you should also check out the maintenance section about database migrations.
You can create users with the new-user
command. Check it out:
flexmeasures add user --help
You can create some pre-determined asset types and data sources with this command:
flexmeasures add initial-structure
You can also create assets in the FlexMeasures UI.
On the command line, you can add many things. Check what data you can add yourself:
flexmeasures add --help
For instance, you can create forecasts for your existing metered data with this command:
flexmeasures add forecasts --help
Check out it's --help
content to learn more. You can set which assets and which time window you want to forecast. Of course, making forecasts takes a while for a larger dataset. You can also simply queue a job with this command (and run a worker to process the redis-queue
).
Just to note, there are also commands to get rid of data. Check:
flexmeasures delete --help
Check out the cli
documentation for more details.
You can visualise the data model like this:
make show-data-model
This will generate a picture based on the model code. You can also generate picture based on the actual database, see inside the Makefile.
Maintenance is supported with the alembic tool. It reacts automatically to almost all changes in the SQLAlchemy code. With alembic, multiple databases, such as development, staging and production databases can be kept in sync.
Run these commands from the repository root directory (read below comments first):
flexmeasures db init
flexmeasures db migrate
flexmeasures db upgrade
The first command (flexmeasures db init
) is only needed here once, it initialises the alembic migration tool. The second command generates the SQL for your current db model and the third actually gives you the db structure.
With every migration, you get a new migration step in migrations/versions
. Be sure to add that to git
, as future calls to flexmeasures db upgrade
will need those steps, and they might happen on another computer.
Hint: You can edit these migrations steps, if you want.
Just to be clear that the db init
command is needed only at the beginning - you usually do, if your model changed:
flexmeasures db migrate --message "Please explain what you did, it helps for later"
flexmeasures db upgrade
Get database structure updated ^^^^^^^^^^^^^^^^^^^^^^^
The goal is that on any other computer, you can always execute
flexmeasures db upgrade
to have the database structure up-to-date with all migrations.
Working with the migration history ^^^^^^^^^^^^^^^^^^^^^^^
The history of migrations is at your fingertips:
flexmeasures db current
flexmeasures db history
You can move back and forth through the history:
flexmeasures db downgrade
flexmeasures db upgrade
Both of these accept a specific revision id parameter, as well.
Check out database status ^^^^^^^^^^^^^^^^^^^^^^^
Log in into the database:
psql -U flexmeasures --password -h 127.0.0.1 -d flexmeasures
with the password from flexmeasures/development_config.py. Check which tables are there:
\dt
To log out:
\q
It is really useful (and therefore an industry standard) to bundle certain database actions within a transaction. Transactions are atomic - either the actions in them all run or the transaction gets rolled back. This keeps the database in a sane state and really helps having expectations during debugging.
Please see the package flexmeasures.data.transactional
for details on how a FlexMeasures developer should make use of this concept. If you are writing a script or a view, you will find there the necessary structural help to bundle your work in a transaction.