FEAT-#6990: Implement lazy execution for the Ray virtual partitions.

modin/core/execution/ray/common/deferred_execution.py

@@ -33,9 +33,11 @@
 from ray.util.client.common import ClientObjectRef
 
 from modin.core.execution.ray.common import MaterializationHook, RayWrapper
+from modin.core.execution.utils import remote_function
 from modin.logging import get_logger
+from modin.utils import _inherit_docstrings
 
-ObjectRefType = Union[ray.ObjectRef, ClientObjectRef, None]
+ObjectRefType = Union[ray.ObjectRef, ClientObjectRef]
 ObjectRefOrListType = Union[ObjectRefType, List[ObjectRefType]]
 ListOrTuple = (list, tuple)
 
@@ -68,16 +70,18 @@ class DeferredExecution:
 
  Attributes
  ----------
- data : ObjectRefType or DeferredExecution
+ data : object
  The execution input.
  func : callable or ObjectRefType
  A function to be executed.
- args : list or tuple
+ args : list or tuple, optional
  Additional positional arguments to be passed in `func`.
- kwargs : dict
+ kwargs : dict, optional
  Additional keyword arguments to be passed in `func`.
- num_returns : int
+ num_returns : int, default: 1
  The number of the return values.
+ flat_data : bool
+ True means that the data is neither DeferredExecution nor list.
  flat_args : bool
  True means that there are no lists or DeferredExecution objects in `args`.
  In this case, no arguments processing is performed and `args` is passed
@@ -88,26 +92,29 @@ class DeferredExecution:
 
  def __init__(
  self,
- data: Union[
- ObjectRefType,
- "DeferredExecution",
- List[Union[ObjectRefType, "DeferredExecution"]],
- ],
+ data: Any,
  func: Union[Callable, ObjectRefType],
- args: Union[List[Any], Tuple[Any]],
- kwargs: Dict[str, Any],
+ args: Union[List[Any], Tuple[Any]] = None,
+ kwargs: Dict[str, Any] = None,
  num_returns=1,
  ):
- if isinstance(data, DeferredExecution):
- data.subscribe()
+ self.flat_data = self._flat_args((data,))
  self.data = data
  self.func = func
- self.args = args
- self.kwargs = kwargs
  self.num_returns = num_returns
- self.flat_args = self._flat_args(args)
- self.flat_kwargs = self._flat_args(kwargs.values())
  self.subscribers = 0
+ if args is not None:
+ self.args = args
+ self.flat_args = self._flat_args(args)
+ else:
+ self.args = ()
+ self.flat_args = True
+ if kwargs is not None:
+ self.kwargs = kwargs
+ self.flat_kwargs = self._flat_args(kwargs.values())
+ else:
+ self.kwargs = {}
+ self.flat_kwargs = True
 
  @classmethod
  def _flat_args(cls, args: Iterable):
@@ -134,7 +141,7 @@ def _flat_args(cls, args: Iterable):
 
  def exec(
  self,
- ) -> Tuple[ObjectRefOrListType, Union["MetaList", List], Union[int, List[int]]]:
+ ) -> Tuple[ObjectRefOrListType, "MetaList", Union[int, List[int]]]:
  """
  Execute this task, if required.
 
@@ -150,7 +157,7 @@ def exec(
  return self.data, self.meta, self.meta_offset
 
  if (
- not isinstance(self.data, DeferredExecution)
+ self.flat_data
  and self.flat_args
  and self.flat_kwargs
  and self.num_returns == 1
@@ -166,19 +173,21 @@ def exec(
  # it back. After the execution, the result is saved and the counter has no effect.
  self.subscribers += 2
  consumers, output = self._deconstruct()
+
  # The last result is the MetaList, so adding +1 here.
  num_returns = sum(c.num_returns for c in consumers) + 1
  results = self._remote_exec_chain(num_returns, *output)
  meta = MetaList(results.pop())
  meta_offset = 0
  results = iter(results)
  for de in consumers:
- if de.num_returns == 1:
+ num_returns = de.num_returns
+ if num_returns == 1:
  de._set_result(next(results), meta, meta_offset)
  meta_offset += 2
  else:
  res = list(islice(results, num_returns))
- offsets = list(range(0, 2 * num_returns, 2))
+ offsets = list(range(meta_offset, meta_offset + 2 * num_returns, 2))
  de._set_result(res, meta, offsets)
  meta_offset += 2 * num_returns
  return self.data, self.meta, self.meta_offset
@@ -303,7 +312,9 @@ def _deconstruct_chain(
  out_extend = output.extend
  while True:
  de.unsubscribe()
- if (out_pos := getattr(de, "out_pos", None)) and not de.has_result:
+ if not (has_result := de.has_result) and (
+ out_pos := getattr(de, "out_pos", None)
+ ):
  out_append(_Tag.REF)
  out_append(out_pos)
  output[out_pos] = out_pos
@@ -318,12 +329,13 @@ def _deconstruct_chain(
  break
  elif not isinstance(data := de.data, DeferredExecution):
  if isinstance(data, ListOrTuple):
+ out_append(_Tag.LIST)
  yield cls._deconstruct_list(
  data, output, stack, result_consumers, out_append
  )
  else:
  out_append(data)
- if not de.has_result:
+ if not has_result:
  stack.append(de)
  break
  else:
@@ -391,22 +403,24 @@ def _deconstruct_list(
  """
  for obj in lst:
  if isinstance(obj, DeferredExecution):
- if out_pos := getattr(obj, "out_pos", None):
+ if obj.has_result:
+ obj = obj.data
+ elif out_pos := getattr(obj, "out_pos", None):
  obj.unsubscribe()
- if obj.has_result:
- out_append(obj.data)
- else:
- out_append(_Tag.REF)
- out_append(out_pos)
- output[out_pos] = out_pos
- if obj.subscribers == 0:
- output[out_pos + 1] = 0
- result_consumers.remove(obj)
+ out_append(_Tag.REF)
+ out_append(out_pos)
+ output[out_pos] = out_pos
+ if obj.subscribers == 0:
+ output[out_pos + 1] = 0
+ result_consumers.remove(obj)
+ continue
  else:
  out_append(_Tag.CHAIN)
  yield cls._deconstruct_chain(obj, output, stack, result_consumers)
  out_append(_Tag.END)
- elif isinstance(obj, ListOrTuple):
+ continue
+
+ if isinstance(obj, ListOrTuple):
  out_append(_Tag.LIST)
  yield cls._deconstruct_list(
  obj, output, stack, result_consumers, out_append
@@ -432,13 +446,13 @@ def _remote_exec_chain(num_returns: int, *args: Tuple) -> List[Any]:
  list
  The execution results. The last element of this list is the ``MetaList``.
  """
- # Prefer _remote_exec_single_chain(). It has fewer arguments and
- # does not require the num_returns to be specified in options.
+ # Prefer _remote_exec_single_chain(). It does not require the num_returns
+ # to be specified in options.
  if num_returns == 2:
  return _remote_exec_single_chain.remote(*args)
  else:
  return _remote_exec_multi_chain.options(num_returns=num_returns).remote(
- num_returns, *args
+ *args
  )
 
  def _set_result(
@@ -456,7 +470,7 @@ def _set_result(
  meta : MetaList
  meta_offset : int or list of int
  """
- del self.func, self.args, self.kwargs, self.flat_args, self.flat_kwargs
+ del self.func, self.args, self.kwargs
  self.data = result
  self.meta = meta
  self.meta_offset = meta_offset
@@ -466,6 +480,64 @@ def __reduce__(self):
  raise NotImplementedError("DeferredExecution is not serializable!")
 
 
+ObjectRefOrDeType = Union[ObjectRefType, DeferredExecution]
+
+
+class DeferredGetItem(DeferredExecution):
+ """
+ Deferred execution task that returns an item at the specified index.
+
+ Parameters
+ ----------
+ data : ObjectRefOrDeType
+ The object to get the item from.
+ index : int
+ The item index.
+ """
+
+ def __init__(self, data: ObjectRefOrDeType, index: int):
+ super().__init__(data, self._remote_fn, [index])
+ self.index = index
+
+ @property
+ @_inherit_docstrings(DeferredExecution.has_result)
+ def has_result(self):
+ if super().has_result:
+ return True
+
+ if (
+ isinstance(self.data, DeferredExecution)
+ and self.data.has_result
+ and self.data.num_returns != 1
+ ):
+ # If `data` is a `DeferredExecution`, that returns multiple results, we
+ # don't need to execute `_remote_fn`, but can get the result by index instead.
+ self._set_result(
+ self.data.data[self.index],
+ self.data.meta,
+ self.data.meta_offset[self.index],
+ )
+ return True
+
+ return False
+
+ @remote_function
+ def _remote_fn(obj, index): # pragma: no cover
+ """
+ Return the item by index.
+
+ Parameters
+ ----------
+ obj : collection
+ index : int
+
+ Returns
+ -------
+ object
+ """
+ return obj[index]
+
+
 class MetaList:
  """
  Meta information, containing the result lengths and the worker address.
@@ -478,6 +550,11 @@ class MetaList:
  def __init__(self, obj: Union[ray.ObjectID, ClientObjectRef, List]):
  self._obj = obj
 
+ def materialize(self):
+ """Materialized the list, if required."""
+ if not isinstance(self._obj, list):
+ self._obj = RayWrapper.materialize(self._obj)
+
  def __getitem__(self, index):
  """
  Get item at the specified index.
@@ -508,21 +585,21 @@ def __setitem__(self, index, value):
  obj[index] = value
 
 
-class MetaListHook(MaterializationHook):
+class MetaListHook(MaterializationHook, DeferredGetItem):
  """
  Used by MetaList.__getitem__() for lazy materialization and getting a single value from the list.
 
  Parameters
  ----------
  meta : MetaList
  Non-materialized list to get the value from.
- idx : int
+ index : int
  The value index in the list.
  """
 
- def __init__(self, meta: MetaList, idx: int):
+ def __init__(self, meta: MetaList, index: int):
+ super().__init__(meta._obj, index)
  self.meta = meta
- self.idx = idx
 
  def pre_materialize(self):
  """
@@ -533,7 +610,7 @@ def pre_materialize(self):
  object
  """
  obj = self.meta._obj
- return obj[self.idx] if isinstance(obj, list) else obj
+ return obj[self.index] if isinstance(obj, list) else obj
 
  def post_materialize(self, materialized):
  """
@@ -548,7 +625,7 @@ def post_materialize(self, materialized):
  object
  """
  self.meta._obj = materialized
- return materialized[self.idx]
+ return materialized[self.index]
 
 
 class _Tag(Enum): # noqa: PR01
@@ -605,7 +682,7 @@ def exec_func(fn: Callable, obj: Any, args: Tuple, kwargs: Dict) -> Any:
  raise err
 
  @classmethod
- def construct(cls, num_returns: int, args: Tuple): # pragma: no cover
+ def construct(cls, args: Tuple): # pragma: no cover
  """
  Construct and execute the specified chain.
 
@@ -615,7 +692,6 @@ def construct(cls, num_returns: int, args: Tuple): # pragma: no cover
 
  Parameters
  ----------
- num_returns : int
  args : tuple
 
  Yields
@@ -687,7 +763,7 @@ def construct_chain(
 
  while chain:
  fn = pop()
- if fn == tg_e:
+ if fn is tg_e:
  lst.append(obj)
  break
 
@@ -717,10 +793,10 @@ def construct_chain(
 
  itr = iter([obj] if num_returns == 1 else obj)
  for _ in range(num_returns):
- obj = next(itr)
- meta.append(len(obj) if hasattr(obj, "__len__") else 0)
- meta.append(len(obj.columns) if hasattr(obj, "columns") else 0)
- yield obj
+ o = next(itr)
+ meta.append(len(o) if hasattr(o, "__len__") else 0)
+ meta.append(len(o.columns) if hasattr(o, "columns") else 0)
+ yield o
 
  @classmethod
  def construct_list(
@@ -834,20 +910,18 @@ def _remote_exec_single_chain(
  -------
  Generator
  """
- return remote_executor.construct(num_returns=2, args=args)
+ return remote_executor.construct(args=args)
 
 
 @ray.remote
 def _remote_exec_multi_chain(
- num_returns: int, *args: Tuple, remote_executor=_REMOTE_EXEC
+ *args: Tuple, remote_executor=_REMOTE_EXEC
 ) -> Generator: # pragma: no cover
  """
  Execute the deconstructed chain with a multiple return values in a worker process.
 
  Parameters
  ----------
- num_returns : int
- The number of return values.
  *args : tuple
  A deconstructed chain to be executed.
  remote_executor : _RemoteExecutor, default: _REMOTE_EXEC
@@ -857,4 +931,4 @@ def _remote_exec_multi_chain(
  -------
  Generator
  """
- return remote_executor.construct(num_returns, args)
+ return remote_executor.construct(args)