Source code for vineyard.io.dataframe

#! /usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright 2020-2022 Alibaba Group Holding Limited.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

''' This module exposes support for DataframeStream, that use can used like:

.. code:: python

    # create a builder, then seal it as stream
    >>> stream = DataframeStream.new(client)
    >>> stream = builder.seal(client)
    >>> stream
    DataframeStream <o0001e09ddd98fd70>

    # use write to put chunks
    >>> writer = stream.open_writer(client)
    >>> writer.write_table(
            pa.Table.from_pandas(
                pd.DataFrame({"x": [1,2,3], "y": [4,5,6]})))

    # mark the stream as finished
    >>> writer.finish()

    # open a reader
    >>> reader = stream.open_reader(client)
    >>> batch = reader.next()
    >>> batch
    pyarrow.RecordBatch
    x: int64
    y: int64

    # the reader reaches the end of the stream
    >>> batch = reader.next()
    ---------------------------------------------------------------------------
    StreamDrainedException                    Traceback (most recent call last)
    ~/libvineyard/python/vineyard/io/dataframe.py in next(self)
        97             try:
    ---> 98                 buffer = self._client.next_buffer_chunk(self._stream)
        99                 with pa.ipc.open_stream(buffer) as reader:

    StreamDrainedException: Stream drain: Stream drained: no more chunks

    The above exception was the direct cause of the following exception:

    StopIteration                             Traceback (most recent call last)
    <ipython-input-11-10f09bf65f8a> in <module>
    ----> 1 batch = reader.next()

    ~/libvineyard/python/vineyard/io/dataframe.py in next(self)
        100                     return reader.read_next_batch()
        101             except StreamDrainedException as e:
    --> 102                 raise StopIteration('No more chunks') from e
        103
        104         def __str__(self) -> str:

    StopIteration: No more chunks
'''

import json
from io import BytesIO
from typing import Dict

import pyarrow as pa
import pyarrow.ipc  # pylint: disable=unused-import

from .._C import ObjectID
from .._C import ObjectMeta
from .._C import StreamDrainedException
from .._C import memory_copy
from .stream import BaseStream


[docs]class DataframeStream(BaseStream): def __init__(self, meta: ObjectMeta, params: Dict = None): super().__init__(meta) self._params = params @property def params(self): return self._params @staticmethod def new(client, params: Dict = None, meta: ObjectMeta = None) -> "DataframeStream": if meta is None: meta = ObjectMeta() meta['typename'] = 'vineyard::DataframeStream' if params is None: params = dict() meta['params_'] = params meta = client.create_metadata(meta) client.create_stream(meta.id) return DataframeStream(meta, params) class Reader(BaseStream.Reader): def __init__(self, client, stream: ObjectID): super().__init__(client, stream) def next(self) -> pa.RecordBatch: try: buffer = self._client.next_buffer_chunk(self._stream) with pa.ipc.open_stream(buffer) as reader: return reader.read_next_batch() except StreamDrainedException as e: raise StopIteration('No more chunks') from e def read_table(self) -> pa.Table: batches = [] while True: try: batches.append(self.next()) except StopIteration: break return pa.Table.from_batches(batches) class Writer(BaseStream.Writer): def __init__(self, client, stream: ObjectID): super().__init__(client, stream) self._buffer = BytesIO() def next(self, size: int) -> memoryview: return self._client.new_buffer_chunk(self._stream, size) def write(self, batch: pa.RecordBatch): sink = BytesIO() with pa.ipc.new_stream(sink, batch.schema) as writer: writer.write(batch) view = sink.getbuffer() if len(view) > 0: buffer = self.next(len(view)) memory_copy(buffer, 0, view) def write_table(self, table: pa.Table): for batch in table.to_batches(): self.write(batch) def finish(self): return self._client.stop_stream(self._stream, False) def _open_new_reader(self, client): return DataframeStream.Reader(client, self.id) def _open_new_writer(self, client): return DataframeStream.Writer(client, self.id)
def dataframe_stream_resolver(obj): meta = obj.meta if 'params_' in meta: params = json.loads(meta['params_']) else: params = dict return DataframeStream(obj.meta, params) def register_dataframe_stream_types(_builder_ctx, resolver_ctx): if resolver_ctx is not None: resolver_ctx.register('vineyard::DataframeStream', dataframe_stream_resolver)