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# The ASF licenses this file to You under the Apache License, Version 2.0
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# http://www.apache.org/licenses/LICENSE-2.0
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from __future__ import absolute_import
from typing import Any
from typing import Iterable
from typing import Tuple
from typing import TypeVar
import pandas as pd
Frame = TypeVar('Frame', bound=pd.core.generic.NDFrame)
[docs]class Partitioning(object):
"""A class representing a (consistent) partitioning of dataframe objects.
"""
[docs] def is_subpartitioning_of(self, other):
# type: (Partitioning) -> bool
"""Returns whether self is a sub-partition of other.
Specifically, returns whether something partitioned by self is necissarily
also partitioned by other.
"""
raise NotImplementedError
[docs] def partition_fn(self, df):
# type: (Frame) -> Iterable[Tuple[Any, Frame]]
"""A callable that actually performs the partitioning of a Frame df.
This will be invoked via a FlatMap in conjunction with a GroupKey to
achieve the desired partitioning.
"""
raise NotImplementedError
[docs]class Index(Partitioning):
"""A partitioning by index (either fully or partially).
If the set of "levels" of the index to consider is not specified, the entire
index is used.
These form a partial order, given by
Nothing() < Index([i]) < Index([i, j]) < ... < Index() < Singleton()
The ordering is implemented via the is_subpartitioning_of method, where the
examples on the right are subpartitionings of the examples on the left above.
"""
_INDEX_PARTITIONS = 10
def __init__(self, levels=None):
self._levels = levels
def __eq__(self, other):
return type(self) == type(other) and self._levels == other._levels
def __ne__(self, other):
return not self == other
def __hash__(self):
if self._levels:
return hash(tuple(sorted(self._levels)))
else:
return hash(type(self))
[docs] def is_subpartitioning_of(self, other):
if isinstance(other, Nothing):
return True
elif isinstance(other, Index):
if self._levels is None:
return True
elif other._levels is None:
return False
else:
return all(level in other._levels for level in self._levels)
else:
return False
[docs] def partition_fn(self, df):
if self._levels is None:
levels = list(range(df.index.nlevels))
else:
levels = self._levels
hashes = sum(
pd.util.hash_array(df.index.get_level_values(level))
for level in levels)
for key in range(self._INDEX_PARTITIONS):
yield key, df[hashes % self._INDEX_PARTITIONS == key]
[docs]class Singleton(Partitioning):
"""A partitioning of all the data into a single partition.
"""
def __eq__(self, other):
return type(self) == type(other)
def __ne__(self, other):
return not self == other
def __hash__(self):
return hash(type(self))
[docs] def is_subpartitioning_of(self, other):
return True
[docs] def partition_fn(self, df):
yield None, df
[docs]class Nothing(Partitioning):
"""A partitioning imposing no constraints on the actual partitioning.
"""
def __eq__(self, other):
return type(self) == type(other)
def __ne__(self, other):
return not self == other
def __hash__(self):
return hash(type(self))
[docs] def is_subpartitioning_of(self, other):
return isinstance(other, Nothing)