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|
# -*- coding: utf-8 -
#
# This file is part of couchdbkit released under the MIT license.
# See the NOTICE for more information.
"""
module to fetch and stream changes from a database
"""
from .utils import json
class ChangesStream(object):
"""\
Change stream object.
.. code-block:: python
from couchdbkit import Server from couchdbkit.changes import ChangesStream
s = Server()
db = s['testdb']
stream = ChangesStream(db)
print "got change now"
for c in stream:
print c
print "stream changes"
with ChangesStream(db, feed="continuous", heartbeat=True) as stream:
for c in stream: print c
"""
def __init__(self, db, **params):
self.db = db
self.params = params
def __enter__(self):
return self
def __exit__(self, *args):
return False
def __iter__(self):
r = self.db.res.get("_changes", **self.params)
with r.body_stream() as body:
while True:
line = body.readline()
if not line:
break
if line.endswith("\r\n"):
line = line[:-2]
else:
line = line[:-1]
if not line:
#heartbeat
continue
if line.endswith(","):
line = line[:-1]
ret = self._parse_change(line)
if not ret:
continue
yield ret
def _parse_change(self, line):
if line.startswith('{"results":') or line.startswith('"last_seq'):
return None
else:
try:
obj = json.loads(line)
return obj
except ValueError:
return None
def __next__(self):
return self
def fold(db, fun, acc, since=0):
"""Fold each changes and accuumulate result using a function
Args:
@param db: Database, a database object
@param fun: function, a callable with arity 2
@param since: int, sequence where to start the feed
@return: list, last acc returned
Ex of function:
fun(change_object,acc):
return acc
If the function return "stop", the changes feed will stop.
"""
if not callable(fun):
raise TypeError("fun isn't a callable")
with ChangesStream(db, since=since) as st:
for c in st:
acc = fun(c, acc)
return acc
def foreach(db, fun, since=0):
"""Iter each changes and pass it to the callable"""
if not callable(fun):
raise TypeError("fun isn't a callable")
with ChangesStream(db, since=since) as st:
for c in st:
fun(c)
|
