#Blitz-DB
Blitzdb (or simply blitz) is a document-oriented database for Python. It can be used either as a stand-alone, flat-file database or in conjunction with another database backend such as MongoDB or MySQL.
##Features
- multiple database backends (flat files, Mongo, ...)
- database transactions & operation caching
- automatic object references
- flexible querying syntax
- deep-key indexing
##Use Cases
Blitz can be used as a standalone document store for client application. Originally blitz was designed for use with the checkmate Python code analysis toolkit, where it stores statistical data. Since blitz stores all documents as single JSON files, it is possible to put the whole database under version-control.
##Examples
To get an idea of what you can do with Blitz, here are some examples.
###Creating objects
from blitzdb import Document
class Movie(Document):
pass
class Actor(Document):
pass
the_godfather = Movie({'name': 'The Godfather','year':1972,'pk':1L})
marlon_brando = Actor({'name':'Marlon Brando','pk':1L})
al_pacino = Actor({'name' : 'Al Pacino','pk':1L})###Storing objects in the database:
from blitzdb import FileBackend
backend = FileBackend("/path/to/my/db")
the_godfather.save(backend)
marlon_brando.save(backend)
al_pacino.save(backend)###Retrieving objects from the database:
the_godfather = backend.get(Movie,{'pk':1L})
#or...
the_godfather = backend.get(Movie,{'name' : 'The Godfather'})###Filtering objects
movies_from_1972 = backend.filter(Movie,{'year' : 1972})###Working with transactions
backend.begin()
the_godfather.director = 'Roland Emmerich' #oops...
the_godfather.save()
backend.rollback() #undo the changes...###Creating nested object references
the_godfather.cast = {'Don Vito Corleone' : marlon_brando, 'Michael Corleone' : al_pacino}
#Documents stored within other objects will be automatically converted to database references.
marlon_brando.performances = [the_godfather]
al_pacino.performances = [the_godfather]
marlon_brando.save(backend)
al_pacino.save(backend)
the_godfather.save(backend)
#Will store references to the movies within the documents in the DB###Creation of database indexes and advanced querying
backend.create_index(Actor,'performances')
#Will create an index on the 'performances' field, for fast querying
godfather_cast = backend.filter(Actor,{'movies' : the_godfather})
#Will return 'Al Pacino' and 'Marlon Brando'###Arbitrary filter expressions
star_wars_iv = Movie({'name' : 'Star Wars - Episode IV: A New Hope','year': 1977})
star_wars_iv.save()
movies_from_the_seventies = backend.filter(Movie,{'year': lambda year : True if year >= 1970 and year < 1980 else False})
#Will return Star Wars & The Godfather (man, what a decade!)
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