Reorganize the use of Alembic (fix data-for-change#757)

This patch reorganizes the use of Alembic.

Our current revisions were out of sync and thus irrelevant, so they were removed.

An initial version was made which now contains the instructions to create the entire schema.

The init_db subcommand was removed as users should now use the alembic command to initialize the
schema. Both the README and the CI were updated accordingly.

Contributors that make pull requests which alter the schema should prepare the appropriate alembic
version and commit it with their patch

.appveyor.yml

@@ -30,7 +30,7 @@ test_script:
 
     createdb anyway
 
-    python main.py init_db
+    alembic upgrade head
 
     python main.py process cbs
 

.travis.yml

@@ -35,7 +35,7 @@ install:
 
 before_script:
   - psql -c 'create database anyway;' -U postgres
-  - ./main.py init_db
+  - alembic upgrade head
 
 script:
   - pylint -j $(nproc) anyway tests main.py

README.md

@@ -69,7 +69,7 @@ See the [Wiki](https://github.com/hasadna/anyway/wiki/Setting-up-a-Python-develo
   * bash: `export DATABASE_URL='sqlite:///local.db'`
   * windows shell: `set DATABASE_URL=sqlite:///local.db`
 
-1. First time, create tables: `python main.py init_db`
+1. First time, create tables: `alembic upgrade head`
 1. Optionally, get the [complete accidents file](https://drive.google.com/file/d/0B4yX8HDe1VaTdWdPMXV5c2gycW8/view?usp=sharing) after sending a permission request, and extract it into `/static/data/lms`. Otherwise, you'll use the [example accidents file](https://drive.google.com/file/d/0B4yX8HDe1VaTSjNMUXYyeW4yQkk/view?usp=sharing) that you already got with the code, so no need to get it again.
 1. Populate the data (markers etc.): `python main.py process cbs`: this will take less than an hour if
    you're using the example files (default), but if you have the complete data it may take several
@@ -94,6 +94,16 @@ To run tests: `pylint -j $(nproc) anyway tests && pytest -m "not browser" ./test
 
 If you also wish to run the real browser tests, replace`-m "not browser"` with `--driver Chrome` or specify the browser of your choice. To learn more, read about [pytest-selenium](http://pytest-selenium.readthedocs.io/en/latest/user_guide.html#specifying-a-browser).
 
+## Altering the database schema
+When creating a patch that alters the database schema, you should use generate the appropriate
+[Alembic](http://alembic.zzzcomputing.com/en/latest/index.html) revision by running:
+
+``` shell
+alembic revision --autogenerate -m "Description of the change"
+```
+
+Make sure to commit your revision together with the code.
+
 ## Docker
 See [DOCKER](docs/DOCKER.md)
 

alembic.ini

@@ -0,0 +1,67 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = alembic
+
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# max length of characters to apply to the
+# "slug" field
+#truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; this defaults
+# to alembic/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path
+# version_locations = %(here)s/bar %(here)s/bat alembic/versions
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

alembic/README

@@ -0,0 +1 @@
+Generic single-database configuration.

alembic/env.py

@@ -0,0 +1,74 @@
+from __future__ import with_statement
+import sys
+import os
+from alembic import context
+from logging.config import fileConfig
+
+sys.path.append(os.path.join(os.path.dirname(__file__), ".."))
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+from anyway.database import Base
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = os.environ.get('DATABASE_URL')
+    context.configure(
+        url=url, target_metadata=target_metadata, literal_binds=True)
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    from anyway.utilities import init_flask
+    from flask.ext.sqlalchemy import SQLAlchemy
+    app = init_flask()
+    connectable = SQLAlchemy(app).engine
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

alembic/script.py.mako

@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}