def _test_compression_warns_when_decompress_caches(self, compress):
not_garbage = []
control = [] # copied data
compress_module = globals()[compress]
real_decompress = compress_module.decompress
def decompress(ob):
"""mock decompress function that delegates to the real
decompress but caches the result and a copy of the result.
"""
res = real_decompress(ob)
not_garbage.append(res) # hold a reference to this bytes object
control.append(bytearray(res)) # copy the data here to check later
return res
# types mapped to values to add in place.
rhs = {
np.dtype('float64'): 1.0,
np.dtype('int32'): 1,
np.dtype('object'): 'a',
np.dtype('datetime64[ns]'): np.timedelta64(1, 'ns'),
np.dtype('timedelta64[ns]'): np.timedelta64(1, 'ns'),
}
with patch(compress_module, 'decompress', decompress), \
tm.assert_produces_warning(PerformanceWarning) as ws:
i_rec = self.encode_decode(self.frame, compress=compress)
for k in self.frame.keys():
value = i_rec[k]
expected = self.frame[k]
assert_frame_equal(value, expected)
# make sure that we can write to the new frames even though
# we needed to copy the data
for block in value._data.blocks:
assert block.values.flags.writeable
# mutate the data in some way
block.values[0] += rhs[block.dtype]
for w in ws:
# check the messages from our warnings
if not isinstance(w, DeprecationWarning):
self.assertEqual(
str(w.message),
'copying data after decompressing; this may mean that'
' decompress is caching its result',
)
for buf, control_buf in zip(not_garbage, control):
# make sure none of our mutations above affected the
# original buffers
self.assertEqual(buf, control_buf)
def _test_compression_warns_when_decompress_caches(self, compress):
not_garbage = []
control = [] # copied data
compress_module = globals()[compress]
real_decompress = compress_module.decompress
def decompress(ob):
"""mock decompress function that delegates to the real
decompress but caches the result and a copy of the result.
"""
res = real_decompress(ob)
not_garbage.append(res) # hold a reference to this bytes object
control.append(bytearray(res)) # copy the data here to check later
return res
# types mapped to values to add in place.
rhs = {
np.dtype('float64'): 1.0,
np.dtype('int32'): 1,
np.dtype('object'): 'a',
np.dtype('datetime64[ns]'): np.timedelta64(1, 'ns'),
np.dtype('timedelta64[ns]'): np.timedelta64(1, 'ns'),
}
with patch(compress_module, 'decompress', decompress), \
tm.assert_produces_warning(PerformanceWarning) as ws:
i_rec = self.encode_decode(self.frame, compress=compress)
for k in self.frame.keys():
value = i_rec[k]
expected = self.frame[k]
assert_frame_equal(value, expected)
# make sure that we can write to the new frames even though
# we needed to copy the data
for block in value._data.blocks:
self.assertTrue(block.values.flags.writeable)
# mutate the data in some way
block.values[0] += rhs[block.dtype]
for w in ws:
# check the messages from our warnings
self.assertEqual(
str(w.message),
'copying data after decompressing; this may mean that'
' decompress is caching its result',
)
for buf, control_buf in zip(not_garbage, control):
# make sure none of our mutations above affected the
# original buffers
self.assertEqual(buf, control_buf)
