如何从 pyarrow 缓冲区反序列化 RecordBatch

Question

我的目标是序列化 RecordBatch，将其发送到 websocket 通道并在接收方对其进行反序列化。

接收端，接收到数据包并重构后 pyarrow.lib.Buffer 对象 pa.py_buffer，我是无法将其反序列化回 RecordBatch.

远离 websocket 的样板，这是一个总结了我正在尝试做的事情的片段：

import pyarrow as pa

indicators = [(1, 'A'), (2, 'B')]

id = pa.int16()
name = pa.string()

data = pa.array(indicators, type=pa.struct([('id', id), ('name', name)]))

batch = pa.RecordBatch.from_arrays([data], ['indicators'])

buffer = batch.serialize()

# How to get back a RecordBatch from buffer?
#
# ???

Answer 1

当使用这样的 serialize 方法时，您可以使用 read_record_batch 函数给定一个已知的模式：

>>> pa.ipc.read_record_batch(buffer, batch.schema)
<pyarrow.lib.RecordBatch at 0x7ff412257278>

但这意味着您需要了解接收端的架构。要将其封装在序列化数据中，请改用 RecordBatchStreamWriter：

>>> sink = pa.BufferOutputStream()
>>> writer = pa.RecordBatchStreamWriter(sink, batch.schema)
>>> writer.write_batch(batch)
>>> writer.close()
>>> buf = sink.getvalue()

>>> reader = pa.ipc.open_stream(buf)
>>> reader.read_all()
pyarrow.Table
indicators: struct<id: int16, name: string>
  child 0, id: int16
  child 1, name: string

请参阅 https://arrow.apache.org/docs/python/ipc.html

中的文档

如何从 pyarrow 缓冲区反序列化 RecordBatch

How to deserialize a RecordBatch from a pyarrow Buffer

python

pyarrow