wuttjamaican.db.conf

WuttJamaican - database configuration

wuttjamaican.db.conf.check_alembic_current(config, alembic_config=None)

Compare the current revisions in the app database to those found in the migration scripts.

Parameters:

• config – App config object.

• alembic_config – Alembic config object, if you have one. Otherwise make_alembic_config() will be called.

Returns:

True if the DB already has all migrations applied; False if not.

wuttjamaican.db.conf.get_alembic_scriptdir(config, alembic_config=None)

Get a “Script Directory” object for Alembic.

This allows for inspection of the migration scripts.

Parameters:

• config – App config object.

• alembic_config – Alembic config object, if you have one. Otherwise make_alembic_config() will be called.

Returns:

ScriptDirectory instance

wuttjamaican.db.conf.get_engines(config, prefix)

Construct and return all database engines defined for a given config prefix.

For instance if you have a config file with:

[wutta.db]
keys = default, host
default.url = sqlite:///tmp/default.sqlite
host.url = sqlite:///tmp/host.sqlite

And then you call this function to get those DB engines:

get_engines(config, 'wutta.db')

The result of that will be like:

{'default': Engine(bind='sqlite:///tmp/default.sqlite'),
 'host': Engine(bind='sqlite:///tmp/host.sqlite')}

Parameters:

• config – App config object.

• prefix – Prefix for the config “section” which contains DB connection info.

Returns:

A dictionary of SQLAlchemy engines, with keys matching those found in config.

wuttjamaican.db.conf.get_setting(session, name)

Get a setting value from the DB.

Note that this assumes (for now?) the DB contains a table named setting with (name, value) columns.

Parameters:

• session – App DB session.

• name – Name of the setting to get.

Returns:

Setting value as string, or None.

wuttjamaican.db.conf.make_alembic_config(config)

Make and return a new Alembic config object, based on current app config.

This tries to set the following on the Alembic config:

• config_file_name - set to app’s primary config file

• main option script_location

• main option version_locations

The latter 2 are read normally from app config, then set on the Alembic config via set_main_option().

Note

IIUC, Alembic should not need to attempt to read config values from file, as long as we’re able to set the above explicitly. However we set the config_file_name “just in case” Alembic needs it, but also to ensure it is discoverable from within the env.py script…

When a migration script runs, code within env.py will call make_config() using the filename which it inspects from the Alembic config.

(Confused yet?!)

Returns:

alembic.config.Config instance

wuttjamaican.db.conf.make_engine_from_config(config_dict, prefix='sqlalchemy.', **kwargs)

Construct a new DB engine from configuration dict.

This is a wrapper around upstream sqlalchemy.engine_from_config(). For even broader context of the SQLAlchemy Engine and their configuration, see Engine Configuration.

The purpose of the customization is to allow certain attributes of the engine to be driven by config, whereas the upstream function is more limited in that regard. The following in particular:

• poolclass

• pool_pre_ping

If these options are present in the configuration dict, they will be coerced to appropriate Python equivalents and then passed as kwargs to the upstream function.

An example config file leveraging this feature:

[wutta.db]
default.url = sqlite:///tmp/default.sqlite
default.poolclass = sqlalchemy.pool:NullPool
default.pool_pre_ping = true

Note that if present, the poolclass value must be a “spec” string, as required by load_object().