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from pycassa.types import Column
from cassandra.ttypes import IndexExpression
__all__ = ['ColumnFamilyMap']
def create_instance(cls, **kwargs):
instance = cls()
instance.__dict__.update(kwargs)
return instance
class ColumnFamilyMap(object):
def __init__(self, cls, column_family, columns=None, raw_columns=False):
"""
Construct a ObjectFamily
Parameters
----------
cls : class
Instances of cls are generated on get*() requests
column_family: ColumnFamily
The ColumnFamily to tie with cls
raw_columns: boolean
Whether all columns should be fetched into the raw_columns field in
requests
"""
self.cls = cls
self.column_family = column_family
self.raw_columns = raw_columns
self.dict_class = self.column_family.dict_class
self.columns = self.dict_class()
for name, column in self.cls.__dict__.iteritems():
if not isinstance(column, Column):
continue
self.columns[name] = column
def combine_columns(self, columns):
combined_columns = self.dict_class()
if self.raw_columns:
combined_columns['raw_columns'] = self.dict_class()
for column, type in self.columns.iteritems():
combined_columns[column] = type.default
for column, value in columns.iteritems():
col_cls = self.columns.get(column, None)
if col_cls is not None:
combined_columns[column] = col_cls.unpack(value)
if self.raw_columns:
combined_columns['raw_columns'][column] = value
return combined_columns
def get(self, key, *args, **kwargs):
"""
Fetch a key from a Cassandra server
Parameters
----------
key : str
The key to fetch
columns : [str]
Limit the columns or super_columns fetched to the specified list
column_start : str
Only fetch when a column or super_column is >= column_start
column_finish : str
Only fetch when a column or super_column is <= column_finish
column_reversed : bool
Fetch the columns or super_columns in reverse order. This will do
nothing unless you passed a dict_class to the constructor.
column_count : int
Limit the number of columns or super_columns fetched per key
super_column : str
Fetch only this super_column
read_consistency_level : ConsistencyLevel
Affects the guaranteed replication factor before returning from
any read operation
Returns
-------
Class instance
"""
if 'columns' not in kwargs and not self.column_family.super and not self.raw_columns:
kwargs['columns'] = self.columns.keys()
columns = self.column_family.get(key, *args, **kwargs)
if self.column_family.super:
if 'super_column' not in kwargs:
vals = self.dict_class()
for super_column, subcols in columns.iteritems():
combined = self.combine_columns(subcols)
vals[super_column] = create_instance(self.cls, key=key, super_column=super_column, **combined)
return vals
combined = self.combine_columns(columns)
return create_instance(self.cls, key=key, super_column=kwargs['super_column'], **combined)
combined = self.combine_columns(columns)
return create_instance(self.cls, key=key, **combined)
def get_indexed_slices(self, instance=None, *args, **kwargs):
"""
Fetches a list of KeySlices from a Cassandra server based on an index clause
Parameters
----------
index_clause : IndexClause
Limits the keys that are returned based on expressions that compare
the value of a column to a given value. At least one of the
expressions in the IndexClause must be on an indexed column.
See index_clause.create_index_clause() and create_index_expression().
columns : [str]
Limit the columns or super_columns fetched to the specified list
column_start : str
Only fetch when a column or super_column is >= column_start
column_finish : str
Only fetch when a column or super_column is <= column_finish
column_reversed : bool
Fetch the columns or super_columns in reverse order. This will do
nothing unless you passed a dict_class to the constructor.
column_count : int
Limit the number of columns or super_columns fetched per key
include_timestamp : bool
If true, return a (value, timestamp) tuple for each column
super_column : str
Return columns only in this super_column
read_consistency_level : ConsistencyLevel
Affects the guaranteed replication factor before returning from
any read operation
Returns
-------
Class instance
"""
if 'columns' not in kwargs and not self.column_family.super and not self.raw_columns:
kwargs['columns'] = self.columns.keys()
# Autopack the index clause's values
if instance is not None:
new_exprs = []
for expr in kwargs['index_clause'].expressions:
new_expr = IndexExpression(expr.column_name, expr.op,
value=self.columns[expr.column_name].pack(instance.__dict__[expr.column_name]))
new_exprs.append(new_expr)
kwargs['index_clause'].expressions = new_exprs
keyslice_map = self.column_family.get_indexed_slices(*args, **kwargs)
ret = self.dict_class()
for key, columns in keyslice_map.iteritems():
if self.column_family.super:
if 'super_column' not in kwargs:
vals = self.dict_class()
for super_column, subcols in columns.iteritems():
combined = self.combine_columns(subcols)
vals[super_column] = create_instance(self.cls, key=key, super_column=super_column, **combined)
ret[key] = vals
else:
combined = self.combine_columns(columns)
ret[key] = create_instance(self.cls, key=key, super_column=kwargs['super_column'], **combined)
else:
combined = self.combine_columns(columns)
ret[key] = create_instance(self.cls, key=key, **combined)
return ret
def multiget(self, *args, **kwargs):
"""
Fetch multiple key from a Cassandra server
Parameters
----------
keys : [str]
A list of keys to fetch
columns : [str]
Limit the columns or super_columns fetched to the specified list
column_start : str
Only fetch when a column or super_column is >= column_start
column_finish : str
Only fetch when a column or super_column is <= column_finish
column_reversed : bool
Fetch the columns or super_columns in reverse order. This will do
nothing unless you passed a dict_class to the constructor.
column_count : int
Limit the number of columns or super_columns fetched per key
super_column : str
Fetch only this super_column
read_consistency_level : ConsistencyLevel
Affects the guaranteed replication factor before returning from
any read operation
Returns
-------
{'key': Class instance}
"""
if 'columns' not in kwargs and not self.column_family.super and not self.raw_columns:
kwargs['columns'] = self.columns.keys()
kcmap = self.column_family.multiget(*args, **kwargs)
ret = self.dict_class()
for key, columns in kcmap.iteritems():
if self.column_family.super:
if 'super_column' not in kwargs:
vals = self.dict_class()
for super_column, subcols in columns.iteritems():
combined = self.combine_columns(subcols)
vals[super_column] = create_instance(self.cls, key=key, super_column=super_column, **combined)
ret[key] = vals
else:
combined = self.combine_columns(columns)
ret[key] = create_instance(self.cls, key=key, super_column=kwargs['super_column'], **combined)
else:
combined = self.combine_columns(columns)
ret[key] = create_instance(self.cls, key=key, **combined)
return ret
def get_count(self, *args, **kwargs):
"""
Count the number of columns for a key
Parameters
----------
key : str
The key with which to count columns
Returns
-------
int Count of columns
"""
return self.column_family.get_count(*args, **kwargs)
def get_range(self, *args, **kwargs):
"""
Get an iterator over keys in a specified range
Parameters
----------
start : str
Start from this key (inclusive)
finish : str
End at this key (inclusive)
columns : [str]
Limit the columns or super_columns fetched to the specified list
column_start : str
Only fetch when a column or super_column is >= column_start
column_finish : str
Only fetch when a column or super_column is <= column_finish
column_reversed : bool
Fetch the columns or super_columns in reverse order. This will do
nothing unless you passed a dict_class to the constructor.
column_count : int
Limit the number of columns or super_columns fetched per key
row_count : int
Limit the number of rows fetched
super_column : str
Fetch only this super_column
read_consistency_level : ConsistencyLevel
Affects the guaranteed replication factor before returning from
any read operation
Returns
-------
iterator over Class instance
"""
if 'columns' not in kwargs and not self.column_family.super and not self.raw_columns:
kwargs['columns'] = self.columns.keys()
for key, columns in self.column_family.get_range(*args, **kwargs):
if self.column_family.super:
if 'super_column' not in kwargs:
vals = self.dict_class()
for super_column, subcols in columns.iteritems():
combined = self.combine_columns(subcols)
vals[super_column] = create_instance(self.cls, key=key, super_column=super_column, **combined)
yield vals
else:
combined = self.combine_columns(columns)
yield create_instance(self.cls, key=key, super_column=kwargs['super_column'], **combined)
else:
combined = self.combine_columns(columns)
yield create_instance(self.cls, key=key, **combined)
def insert(self, instance, columns=None):
"""
Insert or update columns for a key
Parameters
----------
instance : Class instance
The key to insert or update the columns at
columns : ['column']
Limit the columns inserted to this list
Returns
-------
int timestamp
"""
insert_dict = {}
if columns is None:
columns = self.columns.keys()
for column in columns:
if instance.__dict__.has_key(column) and instance.__dict__[column] is not None:
insert_dict[column] = self.columns[column].pack(instance.__dict__[column])
if self.column_family.super:
insert_dict = {instance.super_column: insert_dict}
return self.column_family.insert(instance.key, insert_dict)
def remove(self, instance, column=None):
"""
Remove this instance
Parameters
----------
instance : Class instance
Remove the instance where the key is instance.key
column : str
If set, remove only this Column. Doesn't do anything for SuperColumns
Returns
-------
int timestamp
"""
# Hmm, should we only remove the columns specified on construction?
# It's slower, so we'll leave it out.
if self.column_family.super:
return self.column_family.remove(instance.key, column=instance.super_column)
return self.column_family.remove(instance.key, column)
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