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801a9e5f6f
Makes our preprocessing pipeline do transforms in streaming fashion, so users can do larger-then-memory writes. Closes #2082
83 lines
2.4 KiB
Python
83 lines
2.4 KiB
Python
# SPDX-License-Identifier: Apache-2.0
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# SPDX-FileCopyrightText: Copyright The LanceDB Authors
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from typing import List, Optional, Tuple, Union
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import pyarrow as pa
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from ._lancedb import RecordBatchStream
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class AsyncRecordBatchReader:
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"""
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An async iterator over a stream of RecordBatches.
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Also allows access to the schema of the stream
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"""
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def __init__(
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self,
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inner: Union[RecordBatchStream, pa.Table],
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max_batch_length: Optional[int] = None,
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):
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"""
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Attributes
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----------
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schema : pa.Schema
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The schema of the batches produced by the stream.
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Accessing the schema does not consume any data from the stream
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"""
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if isinstance(inner, pa.Table):
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self._inner = self._async_iter_from_table(inner, max_batch_length)
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self.schema: pa.Schema = inner.schema
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elif isinstance(inner, RecordBatchStream):
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self._inner = inner
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self.schema: pa.Schema = inner.schema
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else:
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raise TypeError("inner must be a RecordBatchStream or a Table")
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async def read_all(self) -> List[pa.RecordBatch]:
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"""
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Read all the record batches from the stream
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This consumes the entire stream and returns a list of record batches
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If there are a lot of results this may consume a lot of memory
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"""
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return [batch async for batch in self]
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def __aiter__(self):
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return self
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async def __anext__(self) -> pa.RecordBatch:
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return await self._inner.__anext__()
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@staticmethod
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async def _async_iter_from_table(
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table: pa.Table, max_batch_length: Optional[int] = None
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):
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"""
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Create an AsyncRecordBatchReader from a Table
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This is useful when you have a Table that you want to iterate
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over asynchronously
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"""
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batches = table.to_batches(max_chunksize=max_batch_length)
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for batch in batches:
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yield batch
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def peek_reader(
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reader: pa.RecordBatchReader,
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) -> Tuple[pa.RecordBatch, pa.RecordBatchReader]:
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if not isinstance(reader, pa.RecordBatchReader):
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raise TypeError("reader must be a RecordBatchReader")
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batch = reader.read_next_batch()
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def all_batches():
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yield batch
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yield from reader
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return batch, pa.RecordBatchReader.from_batches(batch.schema, all_batches())
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