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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,139 @@ | ||
| import logging | ||
| from functools import partial | ||
| from typing import List, Union | ||
|
|
||
| import dask.dataframe as dd | ||
| import pandas as pd | ||
|
|
||
| _logger = logging.getLogger() | ||
| _PAYLOAD_COL = "__ktk_shuffle_payload" | ||
|
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||
|
|
||
| def pack_payload_pandas(partition: pd.DataFrame, group_key: List[str]) -> pd.DataFrame: | ||
| try: | ||
| # Technically distributed is an optional dependency | ||
| from distributed.protocol import serialize_bytes | ||
| except ImportError: | ||
| _logger.warning( | ||
| "Shuffle payload columns cannot be compressed since distributed is not installed." | ||
| ) | ||
| return partition | ||
|
|
||
| if partition.empty: | ||
| res = partition[group_key] | ||
| res[_PAYLOAD_COL] = b"" | ||
| else: | ||
| res = partition.groupby( | ||
| group_key, | ||
| sort=False, | ||
| observed=True, | ||
| # Keep the as_index s.t. the group values are not dropped. With this | ||
| # the behaviour seems to be consistent along pandas versions | ||
| as_index=True, | ||
| ).apply(lambda x: pd.Series({_PAYLOAD_COL: serialize_bytes(x)})) | ||
|
|
||
| res = res.reset_index() | ||
| return res | ||
|
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||
|
|
||
| def pack_payload(df: dd.DataFrame, group_key: Union[List[str], str]) -> dd.DataFrame: | ||
| """ | ||
| Pack all payload columns (everything except of group_key) into a single | ||
| columns. This column will contain a single byte string containing the | ||
| serialized and compressed payload data. The payload data is just dead weight | ||
| when reshuffling. By compressing it once before the shuffle starts, this | ||
| saves a lot of memory and network/disk IO. | ||
| Example:: | ||
| >>> import pandas as pd | ||
| ... import dask.dataframe as dd | ||
| ... from dask.dataframe.shuffle import pack_payload | ||
| ... | ||
| ... df = pd.DataFrame({"A": [1, 1] * 2 + [2, 2] * 2 + [3, 3] * 2, "B": range(12)}) | ||
| ... ddf = dd.from_pandas(df, npartitions=2) | ||
| >>> ddf.partitions[0].compute() | ||
| A B | ||
| 0 1 0 | ||
| 1 1 1 | ||
| 2 1 2 | ||
| 3 1 3 | ||
| 4 2 4 | ||
| 5 2 5 | ||
| >>> pack_payload(ddf, "A").partitions[0].compute() | ||
| A __dask_payload_bytes | ||
| 0 1 b'\x03\x00\x00\x00\x00\x00\x00\x00)\x00\x00\x03... | ||
| 1 2 b'\x03\x00\x00\x00\x00\x00\x00\x00)\x00\x00\x03... | ||
| See also https://github.com/dask/dask/pull/6259 | ||
| """ | ||
|
|
||
| if ( | ||
| # https://github.com/pandas-dev/pandas/issues/34455 | ||
| isinstance(df._meta.index, pd.Float64Index) | ||
| # TODO: Try to find out what's going on an file a bug report | ||
| # For datetime indices the apply seems to be corrupt | ||
| # s.t. apply(lambda x:x) returns different values | ||
| or isinstance(df._meta.index, pd.DatetimeIndex) | ||
| ): | ||
| return df | ||
|
|
||
| if not isinstance(group_key, list): | ||
| group_key = [group_key] | ||
|
|
||
| packed_meta = df._meta[group_key] | ||
| packed_meta[_PAYLOAD_COL] = b"" | ||
|
|
||
| _pack_payload = partial(pack_payload_pandas, group_key=group_key) | ||
|
|
||
| return df.map_partitions(_pack_payload, meta=packed_meta) | ||
|
|
||
|
|
||
| def unpack_payload_pandas( | ||
| partition: pd.DataFrame, unpack_meta: pd.DataFrame | ||
| ) -> pd.DataFrame: | ||
| """ | ||
| Revert ``pack_payload_pandas`` and restore packed payload | ||
| unpack_meta: | ||
| A dataframe indicating the schema of the unpacked data. This will be returned in case the input is empty | ||
| """ | ||
| try: | ||
| # Technically distributed is an optional dependency | ||
| from distributed.protocol import deserialize_bytes | ||
| except ImportError: | ||
| _logger.warning( | ||
| "Shuffle payload columns cannot be compressed since distributed is not installed." | ||
| ) | ||
| return partition | ||
|
|
||
| if partition.empty: | ||
| return unpack_meta.iloc[:0] | ||
|
|
||
| mapped = partition[_PAYLOAD_COL].map(deserialize_bytes) | ||
|
|
||
| return pd.concat(mapped.values, copy=False, ignore_index=True) | ||
|
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||
|
|
||
| def unpack_payload(df: dd.DataFrame, unpack_meta: pd.DataFrame) -> dd.DataFrame: | ||
| """Revert payload packing of ``pack_payload`` and restores full dataframe.""" | ||
|
|
||
| if ( | ||
| # https://github.com/pandas-dev/pandas/issues/34455 | ||
| isinstance(df._meta.index, pd.Float64Index) | ||
| # TODO: Try to find out what's going on an file a bug report | ||
| # For datetime indices the apply seems to be corrupt | ||
| # s.t. apply(lambda x:x) returns different values | ||
| or isinstance(df._meta.index, pd.DatetimeIndex) | ||
| ): | ||
| return df | ||
|
|
||
| return df.map_partitions( | ||
| unpack_payload_pandas, unpack_meta=unpack_meta, meta=unpack_meta | ||
| ) |
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