Rom - the Redis object mapper for Python

Copyright 2013-2014 Josiah Carlson

Released under the LGPL license version 2.1 and version 3 (you can choose which you'd like to be bound under).

Updated documentation can be found: http://pythonhosted.org/rom/

Rom is a package whose purpose is to offer active-record style data modeling within Redis from Python, similar to the semantics of Django ORM, SQLAlchemy + Elixir, Google's Appengine datastore, and others.

I was building a personal project, wanted to use Redis to store some of my data, but didn't want to hack it poorly. I looked at the existing Redis object mappers available in Python, but didn't like the features and functionality offered.

Data types:

• Strings (2.x: str/unicode, 3.3+: str), ints, floats, decimals, booleans
• datetime.datetime, datetime.date, datetime.time
• Json columns (for nested structures)
• OneToMany and ManyToOne columns (for model references)
• Non-rom ForeignModel reference support

Indexes:

• Numeric range fetches, searches, and ordering
• Full-word text search (find me entries with col X having words A and B)
• Prefix matching (can be used for prefix-based autocomplete)
• Suffix matching (can be used for suffix-based autocomplete)
• Pattern matching on string-based columns
• All indexing is available when using Redis 2.6.0 and later

Other features:

• Per-thread entity cache (to minimize round-trips, easy saving of all entities)
• The ability to cache query results and get the key for any other use (see: Query.cached_result())

1. Make sure you have Python 2.6, 2.7, or 3.3+ installed
2. Make sure that you have Andy McCurdy's Redis client library installed: https://github.com/andymccurdy/redis-py/ or https://pypi.python.org/pypi/redis
3. Make sure that you have the Python 2 and 3 compatibility library, 'six' installed: https://pypi.python.org/pypi/six
4. (optional) Make sure that you have the hiredis library installed for Python
5. Make sure that you have a Redis server installed and available remotely

6. Update the Redis connection settings for rom via rom.util.set_connection_settings() (other connection update options, including per-model connections, can be read about in the rom.util documentation):

   import redis
   from rom import util
   
   util.set_connection_settings(host='myhost', db=7)

7. Create a model:

   import rom
   
   # All models to be handled by rom must derived from rom.Model
   class User(rom.Model):
       email = rom.String(required=True, unique=True, suffix=True)
       salt = rom.String()
       hash = rom.String()
       created_at = rom.Float(default=time.time)

8. Create an instance of the model and save it:

   PASSES = 32768
   def gen_hash(password, salt=None):
       salt = salt or os.urandom(16)
       comp = salt + password
       out = sha256(comp).digest()
       for i in xrange(PASSES-1):
           out = sha256(out + comp).digest()
       return salt, out
   
   user = User(email='user@host.com')
   user.salt, user.hash = gen_hash(password)
   user.save()
   # session.commit() or session.flush() works too

9. Load and use the object later:

   user = User.get_by(email='user@host.com')
   at_gmail = User.query.endswith(email='@gmail.com').all()

From version 0.25.0 and on, rom assumes that you are using Redis version 2.6 or later, which supports server-side Lua scripting. This allows for the support of multiple unique columns without potentially nasty race conditions and retries. This also allows for the support of prefix, suffix, and pattern matching on certain column types.

If you are using a version of Redis prior to 2.6, you should upgrade Redis. If you are unable or unwilling to upgrade Redis, but you still wish to use rom, you should call rom._disable_lua_writes(), which will prevent you from using features that require Lua scripting support.