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ray-project--ray/python/ray/data/_internal/planner/plan_write_op.py
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2026-07-13 13:17:40 +08:00

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5.4 KiB
Python

import itertools
import uuid
from typing import TYPE_CHECKING, Callable, Iterator, List, Optional, Union
from ray.data._internal.execution.interfaces import PhysicalOperator
from ray.data._internal.execution.interfaces.task_context import TaskContext
from ray.data._internal.execution.operators.map_operator import MapOperator
from ray.data._internal.execution.operators.map_transformer import (
BlockMapTransformFn,
MapTransformer,
)
from ray.data.block import Block, BlockAccessor
from ray.data.context import DataContext
from ray.data.datasource.datasink import Datasink
from ray.data.datasource.datasource import Datasource
if TYPE_CHECKING:
from ray.data._internal.logical.operators import Write
WRITE_UUID_KWARG_NAME = "write_uuid"
# Key for storing pending checkpoint paths for commit phase
PENDING_CHECKPOINTS_KWARG_NAME = "_pending_checkpoints"
def generate_write_fn(
datasink_or_legacy_datasource: Union[Datasink, Datasource], **write_args
) -> Callable[[Iterator[Block], TaskContext], Iterator[Block]]:
def fn(blocks: Iterator[Block], ctx: TaskContext) -> Iterator[Block]:
"""Writes the blocks to the given datasink or legacy datasource.
Outputs the original blocks to be written."""
# Create a copy of the iterator, so we can return the original blocks.
it1, it2 = itertools.tee(blocks, 2)
if isinstance(datasink_or_legacy_datasource, Datasink):
ctx.kwargs["_datasink_write_return"] = datasink_or_legacy_datasource.write(
it1, ctx
)
else:
datasink_or_legacy_datasource.write(it1, ctx, **write_args)
return it2
return fn
def generate_collect_write_stats_fn() -> BlockMapTransformFn:
# If the write op succeeds, the resulting Dataset is a list of
# one Block which contain stats/metrics about the write.
# Otherwise, an error will be raised. The Datasource can handle
# execution outcomes with `on_write_complete()`` and `on_write_failed()``.
def fn(blocks: Iterator[Block], ctx: TaskContext) -> Iterator[Block]:
"""Handles stats collection for block writes."""
block_accessors = [BlockAccessor.for_block(block) for block in blocks]
total_num_rows = sum(ba.num_rows() for ba in block_accessors)
total_size_bytes = sum(ba.size_bytes() for ba in block_accessors)
# NOTE: Write tasks can return anything, so we need to wrap it in a valid block
# type.
import pandas as pd
block = pd.DataFrame(
{
"num_rows": [total_num_rows],
"size_bytes": [total_size_bytes],
"write_return": [ctx.kwargs.get("_datasink_write_return", None)],
}
)
return iter([block])
return BlockMapTransformFn(
fn,
is_udf=False,
disable_block_shaping=True,
)
def plan_write_op(
op: "Write",
physical_children: List[PhysicalOperator],
data_context: DataContext,
) -> PhysicalOperator:
collect_stats_fn = generate_collect_write_stats_fn()
return _plan_write_op_internal(
op,
physical_children,
data_context,
post_transformations=[collect_stats_fn],
)
def _plan_write_op_internal(
op: "Write",
physical_children: List[PhysicalOperator],
data_context: DataContext,
post_transformations: List[BlockMapTransformFn],
pre_transformations: Optional[List[BlockMapTransformFn]] = None,
) -> PhysicalOperator:
"""Plan a write operation with optional pre and post write transformations.
Args:
op: The write operator.
physical_children: The physical children operators.
data_context: The data context.
post_transformations: Transformations to run AFTER the write.
pre_transformations: Transformations to run BEFORE the write.
Useful for 2-phase commit where pending checkpoint is written first.
Returns:
The physical operator for the write operation.
"""
assert len(physical_children) == 1
input_physical_dag = physical_children[0]
datasink = op.datasink_or_legacy_datasource
write_fn = generate_write_fn(datasink, **op.write_args)
# Build transform chain: pre_write -> write -> post_write
pre_transforms = pre_transformations or []
write_transform = BlockMapTransformFn(
write_fn,
is_udf=False,
# NOTE: No need for block-shaping
disable_block_shaping=True,
)
transform_fns = pre_transforms + [write_transform] + post_transformations
map_transformer = MapTransformer(transform_fns)
# Set up on_start callback for datasinks.
# This allows on_write_start to receive the schema from the first input bundle,
# enabling schema-dependent initialization (e.g., Iceberg schema evolution).
on_start = None
if isinstance(datasink, Datasink):
on_start = datasink.on_write_start
map_op = MapOperator.create(
map_transformer,
input_physical_dag,
data_context,
name="Write",
# Add a UUID to write tasks to prevent filename collisions. This a UUID for the
# overall write operation, not the individual write tasks.
map_task_kwargs={WRITE_UUID_KWARG_NAME: uuid.uuid4().hex},
ray_remote_args=op.ray_remote_args,
min_rows_per_bundle=op.min_rows_per_bundled_input,
compute_strategy=op.compute,
on_start=on_start,
)
return map_op