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21 """
22 The public API of couchable consists of:
23 - L{CouchableDb}: The core DB wrapper/access object.
24 - L{packer}: Extends the list of built-in or C types supported.
25 - L{registerDocType}, L{CouchableDoc}: For adding new document classes.
26 - L{registerAttachmentType}, L{CouchableAttachment}: For adding classes to store as attachments.
27 - L{doGzip}, L{doGunzip}: Helper functions for compressing attachments.
28 - L{newid}: Helper function to make document IDs readable.
29
30 For more information, please see:
31 - API docs: U{http://packages.python.org/couchable}
32 - Blog: U{http://blog.nopinch.net/tag/couchable}
33 - Package: U{http://pypi.python.org/pypi/couchable}
34 - Source: U{http://github.com/wickedgrey/couchable}
35
36 Please use the github issue tracker for bugs:
37 - U{http://github.com/wickedgrey/couchable/issues}
38
39 From the README.txt:
40
41 Currently requires:
- Python 2.7
- CouchDB 1.0.1+ (untested on lower, 0.11 will probably work)
- http://pypi.python.org/pypi/CouchDB 0.8+ (untested on lower, 0.7 will probably work)
Source: http://github.com/wickedgrey/couchable
Package: http://pypi.python.org/pypi/couchable
API docs: http://packages.python.org/couchable
Blog: http://blog.nopinch.net/tag/couchable/
Example of Use
===============
import numpy
import couchdb
import couchable
couchable.registerAttachmentType(numpy.ndarray,
lambda obj: obj.dumps(),
lambda data: numpy.loads(data),
'application/octet-stream', gzip=True)
class BaseClass(object):
def __init__(self, shape, type_=numpy.uint16):
self.vol = numpy.zeros(shape, type_)
# ...
class ClassA(object):
def __init__(self, name):
self.name = name
# ...
couchable.registerDocType(ClassA,
lambda obj, cdb: couchable.newid(obj, lambda x: x.name),
lambda obj, cdb: None)
class SubClassB(BaseClass):
def __init__(self, container):
BaseClass.__init__(self, container.vol.shape, numpy.float32, container.pixelLength_mm)
self.container = container
# ...
couchable.registerDocType(SubClassB)
class Container(BaseClass):
def __init__(self):
BaseClass.__init__(self, (300, 400, 200), numpy.bool_)
# ...
couchable.registerDocType(Container)
def main(options, arguments):
cdb = couchable.CouchableDb(options.cdb_name)
view = couchdb.design.ViewDefinition('generic', 'byclass',
'''
function(doc) {
if ('couchable:' in doc) {
info = doc['couchable:'];
emit([info.module, info.class, doc._id], doc);
}
}''')
view.sync(cdb.db)
# ...
viewResult = view(cdb.db, include_docs=True, startkey=['example', 'Container'], endkey=['example', 'Container', {}])
container_list = cdb.load(viewResult.rows)
# ...
Examples of the JSON Structure of Stored Objects
================================================
All of the object dumps are taken from Futon.
>>> import couchable
>>> cdb=couchable.CouchableDb('example')
>>> class SimpleDoc(couchable.CouchableDoc):
... def __init__(self, **kwargs):
... for name, value in kwargs.items():
... setattr(self, name, value)
...
>>> a = SimpleDoc(name='AAA')
>>> cdb.store(a)
'main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7'
{
"_id": "main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7",
"_rev": "1-315ed02172dddb449a4ab38e54b8bb85",
"couchable:": {
"class": "SimpleDoc",
"module": "__main__"
},
"name": "AAA"
}
The key things to note are:
- The automatically generated id includes some hints about the type of the
object. It is only made if the object doesn't have an ID already.
- The object metadata is stored in "couchable:".
- Normal field names are stored at the top level of the object.
>>> a.int_ = 1234
>>> a.long_ = 1234567890L
>>> a.str_ = 'some str'
>>> cdb.store(a)
'main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7'
{
"_id": "main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7",
"_rev": "2-618b01362f076539f1abb481585b2f64",
"couchable:": {
"class": "SimpleDoc",
"module": "__main__"
},
"long_": 1234567890,
"name": "AAA",
"str_": "some str",
"int_": 1234
}
Numbers, strings and lists are stored in native JSON. Dicts with string keys
are as well, though non-string keys are disallowed by JSON, and so require
special handling (see below).
>>> del a.int_
>>> del a.long_
>>> del a.str_
>>> a.tuple_ = (1, 'two', 3.3)
>>> cdb.store(a)
'main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7'
{
"_id": "main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7",
"_rev": "3-a24d5422be27e8dca0f4b4375718bceb",
"name": "AAA",
"couchable:": {
"class": "SimpleDoc",
"module": "__main__"
},
"tuple_": {
"couchable:": {
"args": [
[
1,
"two",
3.3
]
],
"class": "tuple",
"module": "__builtin__",
"kwargs": {
}
}
}
}
Tuples do not have a native JSON representation, so they get treated much like
arbitrary objects do (note: since tuples don't have a __dict__, they need
special case support). Here, the "args" and "kwargs" will be passed into the
constructor of the type when it's time to load this object.
>>> del a.tuple_
>>> a._implementationDetail = 'this is private'
>>> cdb.store(a)
'main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7'
{
"_id": "main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7",
"_rev": "5-5ac8698c7b9567642484e728e60b95b1",
"couchable:": {
"private": {
"_implementationDetail": "this is private"
},
"class": "SimpleDoc",
"module": "__main__"
},
"name": "AAA"
}
CouchDB reserves all top-level fields that start with an underscore. Since
python makes liberal use of underscores to denote "private" or implementation
detail fields, those end up inside of a second-level dictionary inside of the
"couchable:" dict. During loading, these will end up back inside the object
__dict__.
>>> del a._implementationDetail
>>> a.reserved = 'couchable: reserving the string "couchable:" since 2010'
>>> cdb.store(a)
'main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7'
{
"_id": "main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7",
"_rev": "6-a7ef4d2ba59a68128b076cf5d5d0aaee",
"couchable:": {
"class": "SimpleDoc",
"module": "__main__"
},
"reserved": "couchable:append:str:couchable: reserving the string \"couchable:\" since 2010",
"name": "AAA"
}
Any string that starts with "couchable:" is escaped, since couchable makes
heavy use of that prefix. See below.
>>> del a.reserved
>>> a.dict_ = {'foo':'FOO', 123:'bar', (45, 67):'baz'}
>>> cdb.store(a)
'main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7'
{
"_id": "main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7",
"_rev": "7-4706c617a5f8900956c76ecb6f2e2daa",
"couchable:": {
"keys": {
"couchable:key:tuple:(45, 67)": {
"couchable:": {
"args": [[45, 67]],
"class": "tuple",
"module": "__builtin__",
"kwargs": {
}
}
}
},
"class": "SimpleDoc",
"module": "__main__"
},
"dict_": {
"couchable:key:tuple:(45, 67)": "baz",
"foo": "FOO",
"couchable:repr:int:123": "bar"
},
"name": "AAA"
}
As we saw above, tuples are supported using similar structures to those used
by arbitrary objects. However, JSON only supports strings as dictionary keys.
We solve this by replacing the object-as-key with a string that acts as a
pointer to the actual object, which is stored inside doc['couchable:']['keys']
as the full object.
Similarly, ints cannot be JSON dictonary keys, but we can use the int repr to
fully represent the object, and so we do so in-place (note that this wouldn't
work for tuples because tuples can contain arbitrarily complex objects, not
just the ints that we have in the example).
>>> del a.dict_
>>> a.nested = {(1,1):{(2,2):{(3,3):'four'}}}
>>> cdb.store(a)
'main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7'
{
"_id": "main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7",
"_rev": "10-1fe944276e27bef87259857be9d2abd3",
"nested": {
"couchable:key:tuple:(1, 1)": {
"couchable:key:tuple:(2, 2)": {
"couchable:key:tuple:(3, 3)": "four"
}
}
},
"couchable:": {
"keys": {
"couchable:key:tuple:(1, 1)": {
"couchable:": {
"args": [[1, 1]],
"class": "tuple",
"module": "__builtin__",
"kwargs": {
}
}
},
"couchable:key:tuple:(2, 2)": {
"couchable:": {
"args": [[2, 2]],
"class": "tuple",
"module": "__builtin__",
"kwargs": {
}
}
},
"couchable:key:tuple:(3, 3)": {
"couchable:": {
"args": [[3, 3]],
"class": "tuple",
"module": "__builtin__",
"kwargs": {
}
}
}
},
"class": "SimpleDoc",
"module": "__main__"
},
"name": "AAA"
}
Here we have nested dictionaries with tuple keys, and dict values. All of the
tuples are replaced with string pointers, and fully saved in 'keys'. Note
that 'keys' is a *document* level construct, not an object level one. 'keys'
will never appear outside of doc['couchable:'] (at least not outside of naming
coincidences).
>>> del a.nested
>>> b=SimpleDoc(name='BBB')
>>> a.bbb = b
>>> cdb.store(a)
'main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7'
{
"_id": "main__.SimpleDoc:2a208810-467f-4feb-a5bb-98d0beb1e5e7",
"_rev": "11-5eccb48b99431431c9f91b5e84a4ed7b",
"bbb": "couchable:id:main__.SimpleDoc:544a1408-d3f3-41c4-a428-9f0d2d8e2372",
"couchable:": {
"class": "SimpleDoc",
"module": "__main__"
},
"name": "AAA"
}
{
"_id": "main__.SimpleDoc:544a1408-d3f3-41c4-a428-9f0d2d8e2372",
"_rev": "1-577fefe455995539e11c992b7b46e10a",
"couchable:": {
"class": "SimpleDoc",
"module": "__main__"
},
"name": "BBB"
}
Here, we show the behavior when storing multiple objects, each of which is
flagged as needing to be a full document. Similar to the other string
pointers encountered already, couchable:id points to an object stored in an
entirely different document.
42 """
43
44 from core import CouchableDb
45 from core import registerDocType, CouchableDoc
46 from core import registerAttachmentType, CouchableAttachment
47 from core import packer
48 from core import doGzip, doGunzip
49 from core import newid
50