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import threading
from peewee import *
from peewee import Alias
from peewee import CompoundSelectQuery
from peewee import Metadata
from peewee import callable_
from peewee import __deprecated__
_clone_set = lambda s: set(s) if s else set()
def model_to_dict(model, recurse=True, backrefs=False, only=None,
exclude=None, seen=None, extra_attrs=None,
fields_from_query=None, max_depth=None, manytomany=False):
"""
Convert a model instance (and any related objects) to a dictionary.
:param bool recurse: Whether foreign-keys should be recursed.
:param bool backrefs: Whether lists of related objects should be recursed.
:param only: A list (or set) of field instances indicating which fields
should be included.
:param exclude: A list (or set) of field instances that should be
excluded from the dictionary.
:param list extra_attrs: Names of model instance attributes or methods
that should be included.
:param SelectQuery fields_from_query: Query that was source of model. Take
fields explicitly selected by the query and serialize them.
:param int max_depth: Maximum depth to recurse, value <= 0 means no max.
:param bool manytomany: Process many-to-many fields.
"""
max_depth = -1 if max_depth is None else max_depth
if max_depth == 0:
recurse = False
only = _clone_set(only)
extra_attrs = _clone_set(extra_attrs)
should_skip = lambda n: (n in exclude) or (only and (n not in only))
if fields_from_query is not None:
for item in fields_from_query._returning:
if isinstance(item, Field):
only.add(item)
elif isinstance(item, Alias):
extra_attrs.add(item._alias)
data = {}
exclude = _clone_set(exclude)
seen = _clone_set(seen)
exclude |= seen
model_class = type(model)
if manytomany:
for name, m2m in model._meta.manytomany.items():
if should_skip(name):
continue
exclude.update((m2m, m2m.rel_model._meta.manytomany[m2m.backref]))
for fkf in m2m.through_model._meta.refs:
exclude.add(fkf)
accum = []
for rel_obj in getattr(model, name):
accum.append(model_to_dict(
rel_obj,
recurse=recurse,
backrefs=backrefs,
only=only,
exclude=exclude,
max_depth=max_depth - 1))
data[name] = accum
for field in model._meta.sorted_fields:
if should_skip(field):
continue
field_data = model.__data__.get(field.name)
if isinstance(field, ForeignKeyField) and recurse:
if field_data is not None:
seen.add(field)
rel_obj = getattr(model, field.name)
field_data = model_to_dict(
rel_obj,
recurse=recurse,
backrefs=backrefs,
only=only,
exclude=exclude,
seen=seen,
max_depth=max_depth - 1)
else:
field_data = None
data[field.name] = field_data
if extra_attrs:
for attr_name in extra_attrs:
attr = getattr(model, attr_name)
if callable_(attr):
data[attr_name] = attr()
else:
data[attr_name] = attr
if backrefs and recurse:
for foreign_key, rel_model in model._meta.backrefs.items():
if foreign_key.backref == '+': continue
descriptor = getattr(model_class, foreign_key.backref)
if descriptor in exclude or foreign_key in exclude:
continue
if only and (descriptor not in only) and (foreign_key not in only):
continue
accum = []
exclude.add(foreign_key)
related_query = getattr(model, foreign_key.backref)
for rel_obj in related_query:
accum.append(model_to_dict(
rel_obj,
recurse=recurse,
backrefs=backrefs,
only=only,
exclude=exclude,
max_depth=max_depth - 1))
data[foreign_key.backref] = accum
return data
def update_model_from_dict(instance, data, ignore_unknown=False):
meta = instance._meta
backrefs = dict([(fk.backref, fk) for fk in meta.backrefs])
for key, value in data.items():
if key in meta.combined:
field = meta.combined[key]
is_backref = False
elif key in backrefs:
field = backrefs[key]
is_backref = True
elif ignore_unknown:
setattr(instance, key, value)
continue
else:
raise AttributeError('Unrecognized attribute "%s" for model '
'class %s.' % (key, type(instance)))
is_foreign_key = isinstance(field, ForeignKeyField)
if not is_backref and is_foreign_key and isinstance(value, dict):
try:
rel_instance = instance.__rel__[field.name]
except KeyError:
rel_instance = field.rel_model()
setattr(
instance,
field.name,
update_model_from_dict(rel_instance, value, ignore_unknown))
elif is_backref and isinstance(value, (list, tuple)):
instances = [
dict_to_model(field.model, row_data, ignore_unknown)
for row_data in value]
for rel_instance in instances:
setattr(rel_instance, field.name, instance)
setattr(instance, field.backref, instances)
else:
setattr(instance, field.name, value)
return instance
def dict_to_model(model_class, data, ignore_unknown=False):
return update_model_from_dict(model_class(), data, ignore_unknown)
def insert_where(cls, data, where=None):
"""
Helper for generating conditional INSERT queries.
For example, prevent INSERTing a new tweet if the user has tweeted within
the last hour::
INSERT INTO "tweet" ("user_id", "content", "timestamp")
SELECT 234, 'some content', now()
WHERE NOT EXISTS (
SELECT 1 FROM "tweet"
WHERE user_id = 234 AND timestamp > now() - interval '1 hour')
Using this helper:
cond = ~fn.EXISTS(Tweet.select().where(
Tweet.user == user_obj,
Tweet.timestamp > one_hour_ago))
iq = insert_where(Tweet, {
Tweet.user: user_obj,
Tweet.content: 'some content'}, where=cond)
res = iq.execute()
"""
for field, default in cls._meta.defaults.items():
if field.name in data or field in data: continue
value = default() if callable_(default) else default
data[field] = value
fields, values = zip(*data.items())
sq = Select(columns=values).where(where)
return cls.insert_from(sq, fields).as_rowcount()
class ReconnectMixin(object):
"""
Mixin class that attempts to automatically reconnect to the database under
certain error conditions.
For example, MySQL servers will typically close connections that are idle
for 28800 seconds ("wait_timeout" setting). If your application makes use
of long-lived connections, you may find your connections are closed after
a period of no activity. This mixin will attempt to reconnect automatically
when these errors occur.
This mixin class probably should not be used with Postgres (unless you
REALLY know what you are doing) and definitely has no business being used
with Sqlite. If you wish to use with Postgres, you will need to adapt the
`reconnect_errors` attribute to something appropriate for Postgres.
"""
reconnect_errors = (
# Error class, error message fragment (or empty string for all).
(OperationalError, '2006'), # MySQL server has gone away.
(OperationalError, '2013'), # Lost connection to MySQL server.
(OperationalError, '2014'), # Commands out of sync.
(OperationalError, '4031'), # Client interaction timeout.
# mysql-connector raises a slightly different error when an idle
# connection is terminated by the server. This is equivalent to 2013.
(OperationalError, 'MySQL Connection not available.'),
# Postgres error examples:
#(OperationalError, 'terminat'),
#(InterfaceError, 'connection already closed'),
)
def __init__(self, *args, **kwargs):
super(ReconnectMixin, self).__init__(*args, **kwargs)
# Normalize the reconnect errors to a more efficient data-structure.
self._reconnect_errors = {}
for exc_class, err_fragment in self.reconnect_errors:
self._reconnect_errors.setdefault(exc_class, [])
self._reconnect_errors[exc_class].append(err_fragment.lower())
def execute_sql(self, sql, params=None, commit=None):
if commit is not None:
__deprecated__('"commit" has been deprecated and is a no-op.')
try:
return super(ReconnectMixin, self).execute_sql(sql, params)
except Exception as exc:
# If we are in a transaction, do not reconnect silently as
# any changes could be lost.
if self.in_transaction():
raise exc
exc_class = type(exc)
if exc_class not in self._reconnect_errors:
raise exc
exc_repr = str(exc).lower()
for err_fragment in self._reconnect_errors[exc_class]:
if err_fragment in exc_repr:
break
else:
raise exc
if not self.is_closed():
self.close()
self.connect()
return super(ReconnectMixin, self).execute_sql(sql, params)
def resolve_multimodel_query(query, key='_model_identifier'):
mapping = {}
accum = [query]
while accum:
curr = accum.pop()
if isinstance(curr, CompoundSelectQuery):
accum.extend((curr.lhs, curr.rhs))
continue
model_class = curr.model
name = model_class._meta.table_name
mapping[name] = model_class
curr._returning.append(Value(name).alias(key))
def wrapped_iterator():
for row in query.dicts().iterator():
identifier = row.pop(key)
model = mapping[identifier]
yield model(**row)
return wrapped_iterator()
class ThreadSafeDatabaseMetadata(Metadata):
"""
Metadata class to allow swapping database at run-time in a multi-threaded
application. To use:
class Base(Model):
class Meta:
model_metadata_class = ThreadSafeDatabaseMetadata
"""
def __init__(self, *args, **kwargs):
# The database attribute is stored in a thread-local.
self._database = None
self._local = threading.local()
super(ThreadSafeDatabaseMetadata, self).__init__(*args, **kwargs)
def _get_db(self):
return getattr(self._local, 'database', self._database)
def _set_db(self, db):
if self._database is None:
self._database = db
self._local.database = db
database = property(_get_db, _set_db)