meuhdb 0.3.0

Install

To install the latest release:

pip install meuhdb

… but since this is a very early release, you’d better stick to this Github source repository. You may want to read the Changelog, too.

Basic usage

>>> from meuhdb import MeuhDb
>>> db = MeuhDb()  # Create in-memory database
>>> db.set('one', {'name': 'Alice', 'good': True, 'chief': True})
>>> db.set('two', {'name': 'Bob', 'good': True})
>>> db.set('three', {'name': 'Carl', 'good': False})
>>> db.filter(name='Alice')
{'one': {'chief': True, 'good': True, 'name': 'Alice'}}
>>> db.filter(good=True)
{'two': {'good': True, 'name': 'Bob'}, 'one': {'chief': True, 'good': True, 'name': 'Alice'}}
>>> db.filter(good=True, chief=True)  # More than one criteria, it's a "AND"
{'one': {'chief': True, 'good': True, 'name': 'Alice'}
>>> db.delete('one')
>>> db.filter(name='Alice')
{}
>>> db.exists('one')
False
>>> db.insert({'name': 'John'})
'eb3c3a1d-8999-4052-9e3c-2f3542c047b1'
>>> db.update('eb3c3a1d-8999-4052-9e3c-2f3542c047b1', {'age': 42})
>>> db.get('eb3c3a1d-8999-4052-9e3c-2f3542c047b1')
{'age': 42, 'name': 'John'}

At the moment, you can only query on “equalities”, i.e. a strict equality between what you’re looking for and what’s in the JSON fields (no special operator: greater than, different, etc).

The values must be JSON serializable values (dictionaries, does not work with dates, datetimes, sets, etc.)

MeuhDb(
  path=None,
  autocommit=False, autocommit_after=None,
  lazy_indexes=False,
  backend=DEFAULT_BACKEND)

>>> db = MeuhDb('hello.json', autocommit=False, backend='ujson')
>>> db.set('1', {'name': 'Alice'})  # data is not on disk
>>> db.commit()  # saves to disk
>>> db = MeuhDb('hello.json', autocommit=True)
>>> db.all()  # Data is reloaded from the disk
{u'1': {u'name': u'Alice'}}
>>> db.set('2', {'name': 'Bob'})  # data is written on disk

Indexes

MeuhDb supports index creation. You can index one or more fields to accelerate queries.

Example:

>>> db.create_index('name')
>>> db.filter(name='Alice')  # Will use this index

• You don’t have to index all the fields available in your JSON values, only the one you may query on.

• Indexes will be saved on commit() along with the Database.

• if somehow the index is screwed up, simply create it with the recreate argument: db.create_index('name', recreate=True).

db.create_index('name', _type='lazy')

Warnings

This is not a real actual ACID-ready database manager. This will probably suit a “one-user-only” use case. Opening an loading a large file is very I/O consuming. So MeuhDb will never replace a proper NoSQL database system.

Hack

MeuhDb will work with a standard Python 2 distribution. (I’ve got plans to make it Python-3-ready)

Inside a virtualenv, simply clone this repository and install it in dev mode:

git clone https://github.com/brunobord/meuhdb.git
cd meuhdb
pip install -e ./

You may want to install one or more of these packages to be able to pick one of these enhanced backends:

• simplejson,

• jsonlib (or jsonlib-python3),

• yajl,

• ujson

To run the tests, you’ll have to install tox (pip install tox) and simply run the command tox.

License

This software is published under the terms of the MIT License See the LICENSE file for more information.