[GitHub] [iceberg] rdblue commented on a diff in pull request #6645: Python: Parallelize IO

["rdblue (via GitHub)" <gi...@apache.org>]

rdblue commented on code in PR #6645:
URL: https://github.com/apache/iceberg/pull/6645#discussion_r1085884470


##########
python/pyiceberg/io/pyarrow.py:
##########
@@ -470,13 +471,54 @@ def expression_to_pyarrow(expr: BooleanExpression) -> pc.Expression:
     return boolean_expression_visit(expr, _ConvertToArrowExpression())
 
 
+def _file_to_table(
+    fs: FileSystem,
+    task: FileScanTask,
+    bound_row_filter: BooleanExpression,
+    projected_schema: Schema,
+    projected_field_ids: Set[int],
+    case_sensitive: bool,
+) -> pa.Table:
+    _, path = PyArrowFileIO.parse_location(task.file.file_path)
+
+    # Get the schema
+    with fs.open_input_file(path) as fout:
+        parquet_schema = pq.read_schema(fout)
+        schema_raw = parquet_schema.metadata.get(ICEBERG_SCHEMA)
+        if schema_raw is None:
+            raise ValueError(
+                "Iceberg schema is not embedded into the Parquet file, see https://github.com/apache/iceberg/issues/6505"
+            )
+        file_schema = Schema.parse_raw(schema_raw)
+
+    pyarrow_filter = None
+    if bound_row_filter is not AlwaysTrue():
+        translated_row_filter = translate_column_names(bound_row_filter, file_schema, case_sensitive=case_sensitive)
+        bound_file_filter = bind(file_schema, translated_row_filter, case_sensitive=case_sensitive)
+        pyarrow_filter = expression_to_pyarrow(bound_file_filter)
+
+    file_project_schema = prune_columns(file_schema, projected_field_ids, select_full_types=False)
+
+    if file_schema is None:
+        raise ValueError(f"Missing Iceberg schema in Metadata for file: {path}")
+
+    # Prune the stuff that we don't need anyway
+    file_project_schema_arrow = schema_to_pyarrow(file_project_schema)
+
+    arrow_table = ds.dataset(

Review Comment:
   When I was running tests, I noticed that reading into PyArrow became the bottleneck. I think we will probably want to configure the format at least with [`pre_buffer`](https://github.com/apache/iceberg/pull/6590/files#diff-49144c27eab7e03926b0310aa8b513dbeb9c8d2a0d33bacf8dedbd88b4680aacR516). That doesn't need to be done here though.



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