plan tasks

pyiceberg/manifest.py

@@ -105,6 +105,9 @@ def _missing_(cls, value: object) -> Union[None, str]:
                 return member
         return None
 
+    def is_splittable(self) -> bool:
+        return self.name == "AVRO" or self.name == "PARQUET" or self.name == "ORC"
+
     def __repr__(self) -> str:
         """Return the string representation of the FileFormat class."""
         return f"FileFormat.{self.name}"

pyiceberg/table/__init__.py

@@ -130,10 +130,12 @@
 from pyiceberg.types import (
     strtobool,
 )
+from pyiceberg.utils.bin_packing import ListPacker as ListPacker
+from pyiceberg.utils.bin_packing import PackingIterator
 from pyiceberg.utils.concurrent import ExecutorFactory
 from pyiceberg.utils.config import Config
 from pyiceberg.utils.deprecated import deprecated, deprecation_message
-from pyiceberg.utils.properties import property_as_bool
+from pyiceberg.utils.properties import property_as_bool, property_as_int
 
 if TYPE_CHECKING:
     import daft
@@ -191,6 +193,15 @@ class TableProperties:
     DELETE_MODE_MERGE_ON_READ = "merge-on-read"
     DELETE_MODE_DEFAULT = DELETE_MODE_COPY_ON_WRITE
 
+    READ_SPLIT_SIZE = "read.split.target-size"
+    READ_SPLIT_SIZE_DEFAULT = 128 * 1024 * 1024  # 128 MB
+
+    READ_SPLIT_LOOKBACK = "read.split.planning-lookback"
+    READ_SPLIT_LOOKBACK_DEFAULT = 10
+
+    READ_SPLIT_OPEN_FILE_COST = "read.split.open-file-cost"
+    READ_SPLIT_OPEN_FILE_COST_DEFAULT = 4 * 1024 * 1024  # 4 MB
+
     DEFAULT_NAME_MAPPING = "schema.name-mapping.default"
     FORMAT_VERSION = "format-version"
     DEFAULT_FORMAT_VERSION = 2
@@ -1229,7 +1240,8 @@ def with_case_sensitive(self: S, case_sensitive: bool = True) -> S:
 
 
 class ScanTask(ABC):
-    pass
+    def size_in_bytes(self) -> int:
+        raise NotImplementedError("size in bytes is not implemented")
 
 
 @dataclass(init=False)
@@ -1253,6 +1265,22 @@ def __init__(
         self.start = start or 0
         self.length = length or data_file.file_size_in_bytes
 
+    def size_in_bytes(self) -> int:
+        return self.length + sum(f.file_size_in_bytes for f in self.delete_files)
+
+
+@dataclass(init=False)
+class CombinedFileScanTask(ScanTask):
+    """Task representing combined multiple file scan tasks."""
+
+    tasks: List[FileScanTask]
+
+    def __init__(self, tasks: List[FileScanTask]) -> None:
+        self.tasks = tasks
+
+    def size_in_bytes(self) -> int:
+        return sum(f.size_in_bytes() for f in self.tasks)
+
 
 def _open_manifest(
     io: FileIO,
@@ -1423,6 +1451,66 @@ def plan_files(self) -> Iterable[FileScanTask]:
             for data_entry in data_entries
         ]
 
+    def _target_split_size(self) -> int:
+        table_value = property_as_int(
+            self.table_metadata.properties, TableProperties.READ_SPLIT_SIZE, TableProperties.READ_SPLIT_SIZE_DEFAULT
+        )
+        return property_as_int(self.options, TableProperties.READ_SPLIT_SIZE, table_value)  # type: ignore
+
+    def _loop_back(self) -> int:
+        table_value = property_as_int(
+            self.table_metadata.properties, TableProperties.READ_SPLIT_LOOKBACK, TableProperties.READ_SPLIT_LOOKBACK_DEFAULT
+        )
+        return property_as_int(self.options, TableProperties.READ_SPLIT_LOOKBACK, table_value)  # type: ignore
+
+    def _split_open_file_cost(self) -> int:
+        table_value = property_as_int(
+            self.table_metadata.properties,
+            TableProperties.READ_SPLIT_OPEN_FILE_COST,
+            TableProperties.READ_SPLIT_OPEN_FILE_COST_DEFAULT,
+        )
+        return property_as_int(self.options, TableProperties.READ_SPLIT_OPEN_FILE_COST, table_value)  # type: ignore
+
+    def plan_task(self) -> Iterable[CombinedFileScanTask]:
+        """Plan balanced combined tasks for this scan by splitting large and combining small tasks.
+
+        Returns:
+            List of CombinedFileScanTasks
+        """
+        split_size = self._target_split_size()
+        loop_back = self._loop_back()
+        open_file_cost = self._split_open_file_cost()
+
+        def split(task: FileScanTask) -> List[FileScanTask]:
+            data_file = task.file
+            if not data_file.split_offsets:
+                return [task]
+
+            split_offsets = data_file.split_offsets
+            if not all(split_offsets[i] <= split_offsets[i + 1] for i in range(len(split_offsets) - 1)):
+                # split offsets are strictly ascending
+                return [task]
+
+            all_tasks = []
+            for i in range(len(split_offsets) - 1):
+                all_tasks.append(
+                    FileScanTask(data_file, task.delete_files, split_offsets[i], split_offsets[i + 1] - split_offsets[i])
+                )
+
+            all_tasks.append(
+                FileScanTask(data_file, task.delete_files, split_offsets[-1], data_file.file_size_in_bytes - split_offsets[-1])
+            )
+
+            return all_tasks
+
+        def weight_func(task: FileScanTask) -> int:
+            return max(task.size_in_bytes(), (1 + len(task.delete_files)) * open_file_cost)
+
+        file_tasks = self.plan_files()
+        split_file_tasks = list(itertools.chain.from_iterable(map(split, file_tasks)))
+        packing_iterator = PackingIterator(split_file_tasks, split_size, loop_back, weight_func, False)
+        return list(map(CombinedFileScanTask, packing_iterator))
+
     def to_arrow(self) -> pa.Table:
         """Read an Arrow table eagerly from this DataScan.
 

tests/integration/test_reads.py

@@ -873,3 +873,48 @@ def test_table_scan_empty_table(catalog: Catalog) -> None:
     result_table = tbl.scan().to_arrow()
 
     assert len(result_table) == 0
+
+
+@pytest.mark.integration
+def test_plan_tasks(session_catalog: Catalog) -> None:
+    from pyiceberg.table import TableProperties
+
+    table_name = "default.test_plan_tasks"
+    try:
+        session_catalog.drop_table(table_name)
+    except NoSuchTableError:
+        pass  # Just to make sure that the table doesn't exist
+
+    tbl = session_catalog.create_table(
+        table_name,
+        Schema(
+            NestedField(1, "number", LongType()),
+        ),
+        properties={TableProperties.PARQUET_ROW_GROUP_LIMIT: "1"},
+    )
+
+    # Write 10 row groups, that should end up as 10 batches
+    entries = 10
+    tbl.append(
+        pa.Table.from_pylist(
+            [
+                {
+                    "number": number,
+                }
+                for number in range(entries)
+            ],
+        )
+    )
+
+    plan_files = list(tbl.scan().plan_files())
+    assert len(plan_files) == 1
+
+    plan_tasks = list(tbl.scan(options={TableProperties.READ_SPLIT_SIZE: 1}).plan_task())
+    assert len(plan_tasks) == 10
+
+    split_offsets = []
+    for task in plan_tasks:
+        assert len(task.tasks) == 1
+        split_offsets.append(task.tasks[0].start)
+
+    assert split_offsets == plan_files[0].file.split_offsets