Fokko commented on code in PR #7831:
URL: https://github.com/apache/iceberg/pull/7831#discussion_r1257807284


##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16
+
+# Serialization rules: 
https://iceberg.apache.org/spec/#binary-single-value-serialization
+#
+# Type      Binary serialization
+# boolean   0x00 for false, non-zero byte for true
+# int       Stored as 4-byte little-endian
+# long      Stored as 8-byte little-endian
+# float     Stored as 4-byte little-endian
+# double    Stored as 8-byte little-endian
+# date      Stores days from the 1970-01-01 in an 4-byte little-endian int
+# time      Stores microseconds from midnight in an 8-byte little-endian long
+# timestamp without zone       Stores microseconds from 1970-01-01 
00:00:00.000000 in an 8-byte little-endian long
+# timestamp with zone  Stores microseconds from 1970-01-01 00:00:00.000000 UTC 
in an 8-byte little-endian long
+# string    UTF-8 bytes (without length)
+# uuid      16-byte big-endian value, see example in Appendix B
+# fixed(L)  Binary value
+# binary    Binary value (without length)
+#
+
+
+def bool_to_avro(value: bool) -> bytes:
+    return struct.pack("?", value)

Review Comment:
   Can we initialize the structs just once? Similar to the Avro reading:
   
   
https://github.com/apache/iceberg/blob/e389e4d139624a49729379acd330dd9c96187b04/python/pyiceberg/avro/__init__.py#L19-L20



##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16

Review Comment:
   In Spark this is configurable, but I'm fine with leaving this as is right 
now.



##########
python/tests/utils/test_file_stats.py:
##########
@@ -0,0 +1,361 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+
+import math
+import struct
+from tempfile import TemporaryDirectory
+from typing import Any, List
+
+import pyarrow as pa
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile
+from pyiceberg.schema import Schema
+from pyiceberg.utils.file_stats import BOUND_TRUNCATED_LENGHT, 
fill_parquet_file_metadata, parquet_schema_to_ids
+
+
+def construct_test_table() -> pa.Buffer:
+    schema = pa.schema(
+        [pa.field("strings", pa.string()), pa.field("floats", pa.float64()), 
pa.field("list", pa.list_(pa.int64()))]

Review Comment:
   Can we also add a map here?



##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16
+
+# Serialization rules: 
https://iceberg.apache.org/spec/#binary-single-value-serialization
+#
+# Type      Binary serialization
+# boolean   0x00 for false, non-zero byte for true
+# int       Stored as 4-byte little-endian
+# long      Stored as 8-byte little-endian
+# float     Stored as 4-byte little-endian
+# double    Stored as 8-byte little-endian
+# date      Stores days from the 1970-01-01 in an 4-byte little-endian int
+# time      Stores microseconds from midnight in an 8-byte little-endian long
+# timestamp without zone       Stores microseconds from 1970-01-01 
00:00:00.000000 in an 8-byte little-endian long
+# timestamp with zone  Stores microseconds from 1970-01-01 00:00:00.000000 UTC 
in an 8-byte little-endian long
+# string    UTF-8 bytes (without length)
+# uuid      16-byte big-endian value, see example in Appendix B
+# fixed(L)  Binary value
+# binary    Binary value (without length)
+#
+
+
+def bool_to_avro(value: bool) -> bytes:
+    return struct.pack("?", value)
+
+
+def int32_to_avro(value: int) -> bytes:
+    return struct.pack("<i", value)
+
+
+def int64_to_avro(value: int) -> bytes:
+    return struct.pack("<q", value)
+
+
+def float_to_avro(value: float) -> bytes:
+    return struct.pack("<f", value)
+
+
+def double_to_avro(value: float) -> bytes:
+    return struct.pack("<d", value)
+
+
+def bytes_to_avro(value: Union[bytes, str]) -> bytes:
+    if type(value) == str:
+        return value.encode()
+    else:
+        assert isinstance(value, bytes)  # appeases mypy
+        return value
+
+
+class StatsAggregator:
+    def __init__(self, type_string: str):
+        self.current_min: Any = None
+        self.current_max: Any = None
+        self.serialize: Any = None
+
+        if type_string == "BOOLEAN":
+            self.serialize = bool_to_avro
+        elif type_string == "INT32":
+            self.serialize = int32_to_avro
+        elif type_string == "INT64":
+            self.serialize = int64_to_avro
+        elif type_string == "INT96":
+            raise NotImplementedError("Statistics not implemented for INT96 
physical type")
+        elif type_string == "FLOAT":
+            self.serialize = float_to_avro
+        elif type_string == "DOUBLE":
+            self.serialize = double_to_avro
+        elif type_string == "BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        elif type_string == "FIXED_LEN_BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        else:
+            raise AssertionError(f"Unknown physical type {type_string}")
+
+    def add_min(self, val: bytes) -> None:
+        if not self.current_min:
+            self.current_min = val
+        elif val < self.current_min:
+            self.current_min = val
+
+    def add_max(self, val: bytes) -> None:
+        if not self.current_max:
+            self.current_max = val
+        elif self.current_max < val:
+            self.current_max = val
+
+    def get_min(self) -> bytes:
+        return self.serialize(self.current_min)[:BOUND_TRUNCATED_LENGHT]
+
+    def get_max(self) -> bytes:
+        return self.serialize(self.current_max)[:BOUND_TRUNCATED_LENGHT]
+
+
+def fill_parquet_file_metadata(
+    df: DataFile, metadata: pq.FileMetaData, col_path_2_iceberg_id: Dict[str, 
int], file_size: int

Review Comment:
   Should we move this one to `pyarrow.py`? This uses PyArrow classes that 
might not be installed.



##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16
+
+# Serialization rules: 
https://iceberg.apache.org/spec/#binary-single-value-serialization
+#
+# Type      Binary serialization
+# boolean   0x00 for false, non-zero byte for true
+# int       Stored as 4-byte little-endian
+# long      Stored as 8-byte little-endian
+# float     Stored as 4-byte little-endian
+# double    Stored as 8-byte little-endian
+# date      Stores days from the 1970-01-01 in an 4-byte little-endian int
+# time      Stores microseconds from midnight in an 8-byte little-endian long
+# timestamp without zone       Stores microseconds from 1970-01-01 
00:00:00.000000 in an 8-byte little-endian long
+# timestamp with zone  Stores microseconds from 1970-01-01 00:00:00.000000 UTC 
in an 8-byte little-endian long
+# string    UTF-8 bytes (without length)
+# uuid      16-byte big-endian value, see example in Appendix B
+# fixed(L)  Binary value
+# binary    Binary value (without length)
+#
+
+
+def bool_to_avro(value: bool) -> bytes:
+    return struct.pack("?", value)
+
+
+def int32_to_avro(value: int) -> bytes:
+    return struct.pack("<i", value)
+
+
+def int64_to_avro(value: int) -> bytes:
+    return struct.pack("<q", value)
+
+
+def float_to_avro(value: float) -> bytes:
+    return struct.pack("<f", value)
+
+
+def double_to_avro(value: float) -> bytes:
+    return struct.pack("<d", value)
+
+
+def bytes_to_avro(value: Union[bytes, str]) -> bytes:
+    if type(value) == str:
+        return value.encode()
+    else:
+        assert isinstance(value, bytes)  # appeases mypy
+        return value
+
+
+class StatsAggregator:
+    def __init__(self, type_string: str):
+        self.current_min: Any = None
+        self.current_max: Any = None
+        self.serialize: Any = None
+
+        if type_string == "BOOLEAN":
+            self.serialize = bool_to_avro
+        elif type_string == "INT32":
+            self.serialize = int32_to_avro
+        elif type_string == "INT64":
+            self.serialize = int64_to_avro
+        elif type_string == "INT96":
+            raise NotImplementedError("Statistics not implemented for INT96 
physical type")
+        elif type_string == "FLOAT":
+            self.serialize = float_to_avro
+        elif type_string == "DOUBLE":
+            self.serialize = double_to_avro
+        elif type_string == "BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        elif type_string == "FIXED_LEN_BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        else:
+            raise AssertionError(f"Unknown physical type {type_string}")
+
+    def add_min(self, val: bytes) -> None:
+        if not self.current_min:
+            self.current_min = val
+        elif val < self.current_min:
+            self.current_min = val
+
+    def add_max(self, val: bytes) -> None:
+        if not self.current_max:

Review Comment:
   ```suggestion
           if self.current_max is not None:
   ```



##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16
+
+# Serialization rules: 
https://iceberg.apache.org/spec/#binary-single-value-serialization
+#
+# Type      Binary serialization
+# boolean   0x00 for false, non-zero byte for true
+# int       Stored as 4-byte little-endian
+# long      Stored as 8-byte little-endian
+# float     Stored as 4-byte little-endian
+# double    Stored as 8-byte little-endian
+# date      Stores days from the 1970-01-01 in an 4-byte little-endian int
+# time      Stores microseconds from midnight in an 8-byte little-endian long
+# timestamp without zone       Stores microseconds from 1970-01-01 
00:00:00.000000 in an 8-byte little-endian long
+# timestamp with zone  Stores microseconds from 1970-01-01 00:00:00.000000 UTC 
in an 8-byte little-endian long
+# string    UTF-8 bytes (without length)
+# uuid      16-byte big-endian value, see example in Appendix B
+# fixed(L)  Binary value
+# binary    Binary value (without length)
+#
+
+
+def bool_to_avro(value: bool) -> bytes:
+    return struct.pack("?", value)
+
+
+def int32_to_avro(value: int) -> bytes:
+    return struct.pack("<i", value)
+
+
+def int64_to_avro(value: int) -> bytes:
+    return struct.pack("<q", value)
+
+
+def float_to_avro(value: float) -> bytes:
+    return struct.pack("<f", value)
+
+
+def double_to_avro(value: float) -> bytes:
+    return struct.pack("<d", value)
+
+
+def bytes_to_avro(value: Union[bytes, str]) -> bytes:
+    if type(value) == str:
+        return value.encode()
+    else:
+        assert isinstance(value, bytes)  # appeases mypy
+        return value
+
+
+class StatsAggregator:
+    def __init__(self, type_string: str):
+        self.current_min: Any = None
+        self.current_max: Any = None
+        self.serialize: Any = None
+
+        if type_string == "BOOLEAN":
+            self.serialize = bool_to_avro
+        elif type_string == "INT32":
+            self.serialize = int32_to_avro
+        elif type_string == "INT64":
+            self.serialize = int64_to_avro
+        elif type_string == "INT96":
+            raise NotImplementedError("Statistics not implemented for INT96 
physical type")
+        elif type_string == "FLOAT":
+            self.serialize = float_to_avro
+        elif type_string == "DOUBLE":
+            self.serialize = double_to_avro
+        elif type_string == "BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        elif type_string == "FIXED_LEN_BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        else:
+            raise AssertionError(f"Unknown physical type {type_string}")
+
+    def add_min(self, val: bytes) -> None:
+        if not self.current_min:
+            self.current_min = val
+        elif val < self.current_min:
+            self.current_min = val
+
+    def add_max(self, val: bytes) -> None:
+        if not self.current_max:
+            self.current_max = val
+        elif self.current_max < val:
+            self.current_max = val
+
+    def get_min(self) -> bytes:
+        return self.serialize(self.current_min)[:BOUND_TRUNCATED_LENGHT]
+
+    def get_max(self) -> bytes:
+        return self.serialize(self.current_max)[:BOUND_TRUNCATED_LENGHT]
+
+
+def fill_parquet_file_metadata(
+    df: DataFile, metadata: pq.FileMetaData, col_path_2_iceberg_id: Dict[str, 
int], file_size: int
+) -> None:
+    """
+    Computes and fills the following fields of the DataFile object.
+
+    - file_format
+    - record_count
+    - file_size_in_bytes
+    - column_sizes
+    - value_counts
+    - null_value_counts
+    - nan_value_counts
+    - lower_bounds
+    - upper_bounds
+    - split_offsets
+
+    Args:
+        df (DataFile): A DataFile object representing the Parquet file for 
which metadata is to be filled.
+        metadata (pyarrow.parquet.FileMetaData): A pyarrow metadata object.
+        col_path_2_iceberg_id: A mapping of column paths as in the 
`path_in_schema` attribute of the colum
+            metadata to iceberg schema IDs. For scalar columns this will be 
the column name. For complex types
+            it could be something like `my_map.key_value.value`
+        file_size (int): The total compressed file size cannot be retrieved 
from the metadata and hence has to
+            be passed here. Depending on the kind of file system and pyarrow 
library call used, different
+            ways to obtain this value might be appropriate.
+    """
+    col_index_2_id = {}
+
+    col_names = set(metadata.schema.names)
+
+    first_group = metadata.row_group(0)
+
+    for c in range(metadata.num_columns):
+        column = first_group.column(c)
+        col_path = column.path_in_schema
+
+        if col_path in col_path_2_iceberg_id:
+            col_index_2_id[c] = col_path_2_iceberg_id[col_path]
+        else:
+            raise AssertionError(f"Column path {col_path} couldn't be mapped 
to an iceberg ID")
+
+    column_sizes: Dict[int, int] = {}
+    value_counts: Dict[int, int] = {}
+    split_offsets: List[int] = []
+
+    null_value_counts: Dict[int, int] = {}
+    nan_value_counts: Dict[int, int] = {}
+
+    col_aggs = {}
+
+    for r in range(metadata.num_row_groups):
+        # References:
+        # 
https://github.com/apache/iceberg/blob/fc381a81a1fdb8f51a0637ca27cd30673bd7aad3/parquet/src/main/java/org/apache/iceberg/parquet/ParquetUtil.java#L232
+        # 
https://github.com/apache/parquet-mr/blob/ac29db4611f86a07cc6877b416aa4b183e09b353/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/metadata/ColumnChunkMetaData.java#L184
+
+        row_group = metadata.row_group(r)
+
+        data_offset = row_group.column(0).data_page_offset
+        dictionary_offset = row_group.column(0).dictionary_page_offset
+
+        if row_group.column(0).has_dictionary_page and dictionary_offset < 
data_offset:
+            split_offsets.append(dictionary_offset)
+        else:
+            split_offsets.append(data_offset)
+
+        for c in range(metadata.num_columns):
+            col_id = col_index_2_id[c]
+
+            column = row_group.column(c)
+
+            column_sizes[col_id] = column_sizes.get(col_id, 0) + 
column.total_compressed_size
+            value_counts[col_id] = value_counts.get(col_id, 0) + 
column.num_values
+
+            if column.is_stats_set:
+                try:
+                    statistics = column.statistics
+
+                    null_value_counts[col_id] = null_value_counts.get(col_id, 
0) + statistics.null_count
+
+                    if column.path_in_schema in col_names:
+                        # Iceberg seems to only have statistics for scalar 
columns
+
+                        if col_id not in col_aggs:
+                            col_aggs[col_id] = 
StatsAggregator(statistics.physical_type)
+
+                        col_aggs[col_id].add_min(statistics.min)

Review Comment:
   Do we need the intermediate `col_aggs`? I would prefer to directly write it 
into `{lower,upper}_bounds`.



##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16
+
+# Serialization rules: 
https://iceberg.apache.org/spec/#binary-single-value-serialization
+#
+# Type      Binary serialization
+# boolean   0x00 for false, non-zero byte for true
+# int       Stored as 4-byte little-endian
+# long      Stored as 8-byte little-endian
+# float     Stored as 4-byte little-endian
+# double    Stored as 8-byte little-endian
+# date      Stores days from the 1970-01-01 in an 4-byte little-endian int
+# time      Stores microseconds from midnight in an 8-byte little-endian long
+# timestamp without zone       Stores microseconds from 1970-01-01 
00:00:00.000000 in an 8-byte little-endian long
+# timestamp with zone  Stores microseconds from 1970-01-01 00:00:00.000000 UTC 
in an 8-byte little-endian long
+# string    UTF-8 bytes (without length)
+# uuid      16-byte big-endian value, see example in Appendix B
+# fixed(L)  Binary value
+# binary    Binary value (without length)
+#
+
+
+def bool_to_avro(value: bool) -> bytes:
+    return struct.pack("?", value)
+
+
+def int32_to_avro(value: int) -> bytes:
+    return struct.pack("<i", value)
+
+
+def int64_to_avro(value: int) -> bytes:
+    return struct.pack("<q", value)
+
+
+def float_to_avro(value: float) -> bytes:
+    return struct.pack("<f", value)
+
+
+def double_to_avro(value: float) -> bytes:
+    return struct.pack("<d", value)
+
+
+def bytes_to_avro(value: Union[bytes, str]) -> bytes:
+    if type(value) == str:
+        return value.encode()
+    else:
+        assert isinstance(value, bytes)  # appeases mypy
+        return value
+
+
+class StatsAggregator:
+    def __init__(self, type_string: str):
+        self.current_min: Any = None
+        self.current_max: Any = None
+        self.serialize: Any = None
+
+        if type_string == "BOOLEAN":
+            self.serialize = bool_to_avro
+        elif type_string == "INT32":
+            self.serialize = int32_to_avro
+        elif type_string == "INT64":
+            self.serialize = int64_to_avro
+        elif type_string == "INT96":
+            raise NotImplementedError("Statistics not implemented for INT96 
physical type")
+        elif type_string == "FLOAT":
+            self.serialize = float_to_avro
+        elif type_string == "DOUBLE":
+            self.serialize = double_to_avro
+        elif type_string == "BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        elif type_string == "FIXED_LEN_BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        else:
+            raise AssertionError(f"Unknown physical type {type_string}")
+
+    def add_min(self, val: bytes) -> None:
+        if not self.current_min:
+            self.current_min = val
+        elif val < self.current_min:
+            self.current_min = val
+
+    def add_max(self, val: bytes) -> None:
+        if not self.current_max:
+            self.current_max = val
+        elif self.current_max < val:
+            self.current_max = val
+
+    def get_min(self) -> bytes:
+        return self.serialize(self.current_min)[:BOUND_TRUNCATED_LENGHT]
+
+    def get_max(self) -> bytes:
+        return self.serialize(self.current_max)[:BOUND_TRUNCATED_LENGHT]
+
+
+def fill_parquet_file_metadata(
+    df: DataFile, metadata: pq.FileMetaData, col_path_2_iceberg_id: Dict[str, 
int], file_size: int
+) -> None:
+    """
+    Computes and fills the following fields of the DataFile object.
+
+    - file_format
+    - record_count
+    - file_size_in_bytes
+    - column_sizes
+    - value_counts
+    - null_value_counts
+    - nan_value_counts
+    - lower_bounds
+    - upper_bounds
+    - split_offsets
+
+    Args:
+        df (DataFile): A DataFile object representing the Parquet file for 
which metadata is to be filled.
+        metadata (pyarrow.parquet.FileMetaData): A pyarrow metadata object.
+        col_path_2_iceberg_id: A mapping of column paths as in the 
`path_in_schema` attribute of the colum
+            metadata to iceberg schema IDs. For scalar columns this will be 
the column name. For complex types
+            it could be something like `my_map.key_value.value`
+        file_size (int): The total compressed file size cannot be retrieved 
from the metadata and hence has to
+            be passed here. Depending on the kind of file system and pyarrow 
library call used, different
+            ways to obtain this value might be appropriate.
+    """
+    col_index_2_id = {}
+
+    col_names = set(metadata.schema.names)
+
+    first_group = metadata.row_group(0)
+
+    for c in range(metadata.num_columns):
+        column = first_group.column(c)
+        col_path = column.path_in_schema
+
+        if col_path in col_path_2_iceberg_id:
+            col_index_2_id[c] = col_path_2_iceberg_id[col_path]
+        else:
+            raise AssertionError(f"Column path {col_path} couldn't be mapped 
to an iceberg ID")
+
+    column_sizes: Dict[int, int] = {}
+    value_counts: Dict[int, int] = {}
+    split_offsets: List[int] = []
+
+    null_value_counts: Dict[int, int] = {}
+    nan_value_counts: Dict[int, int] = {}
+
+    col_aggs = {}
+
+    for r in range(metadata.num_row_groups):
+        # References:
+        # 
https://github.com/apache/iceberg/blob/fc381a81a1fdb8f51a0637ca27cd30673bd7aad3/parquet/src/main/java/org/apache/iceberg/parquet/ParquetUtil.java#L232
+        # 
https://github.com/apache/parquet-mr/blob/ac29db4611f86a07cc6877b416aa4b183e09b353/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/metadata/ColumnChunkMetaData.java#L184
+
+        row_group = metadata.row_group(r)
+
+        data_offset = row_group.column(0).data_page_offset
+        dictionary_offset = row_group.column(0).dictionary_page_offset
+
+        if row_group.column(0).has_dictionary_page and dictionary_offset < 
data_offset:
+            split_offsets.append(dictionary_offset)
+        else:
+            split_offsets.append(data_offset)
+
+        for c in range(metadata.num_columns):
+            col_id = col_index_2_id[c]
+
+            column = row_group.column(c)
+
+            column_sizes[col_id] = column_sizes.get(col_id, 0) + 
column.total_compressed_size
+            value_counts[col_id] = value_counts.get(col_id, 0) + 
column.num_values
+
+            if column.is_stats_set:
+                try:
+                    statistics = column.statistics
+
+                    null_value_counts[col_id] = null_value_counts.get(col_id, 
0) + statistics.null_count
+
+                    if column.path_in_schema in col_names:
+                        # Iceberg seems to only have statistics for scalar 
columns
+
+                        if col_id not in col_aggs:
+                            col_aggs[col_id] = 
StatsAggregator(statistics.physical_type)
+
+                        col_aggs[col_id].add_min(statistics.min)
+                        col_aggs[col_id].add_max(statistics.max)
+
+                except pyarrow.lib.ArrowNotImplementedError:
+                    pass

Review Comment:
   Should we log a warning here?



##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16
+
+# Serialization rules: 
https://iceberg.apache.org/spec/#binary-single-value-serialization
+#
+# Type      Binary serialization
+# boolean   0x00 for false, non-zero byte for true
+# int       Stored as 4-byte little-endian
+# long      Stored as 8-byte little-endian
+# float     Stored as 4-byte little-endian
+# double    Stored as 8-byte little-endian
+# date      Stores days from the 1970-01-01 in an 4-byte little-endian int
+# time      Stores microseconds from midnight in an 8-byte little-endian long
+# timestamp without zone       Stores microseconds from 1970-01-01 
00:00:00.000000 in an 8-byte little-endian long
+# timestamp with zone  Stores microseconds from 1970-01-01 00:00:00.000000 UTC 
in an 8-byte little-endian long
+# string    UTF-8 bytes (without length)
+# uuid      16-byte big-endian value, see example in Appendix B
+# fixed(L)  Binary value
+# binary    Binary value (without length)
+#
+
+
+def bool_to_avro(value: bool) -> bytes:
+    return struct.pack("?", value)
+
+
+def int32_to_avro(value: int) -> bytes:
+    return struct.pack("<i", value)
+
+
+def int64_to_avro(value: int) -> bytes:
+    return struct.pack("<q", value)
+
+
+def float_to_avro(value: float) -> bytes:
+    return struct.pack("<f", value)
+
+
+def double_to_avro(value: float) -> bytes:
+    return struct.pack("<d", value)
+
+
+def bytes_to_avro(value: Union[bytes, str]) -> bytes:
+    if type(value) == str:
+        return value.encode()
+    else:
+        assert isinstance(value, bytes)  # appeases mypy
+        return value
+
+
+class StatsAggregator:
+    def __init__(self, type_string: str):
+        self.current_min: Any = None
+        self.current_max: Any = None
+        self.serialize: Any = None
+
+        if type_string == "BOOLEAN":
+            self.serialize = bool_to_avro
+        elif type_string == "INT32":
+            self.serialize = int32_to_avro
+        elif type_string == "INT64":
+            self.serialize = int64_to_avro
+        elif type_string == "INT96":
+            raise NotImplementedError("Statistics not implemented for INT96 
physical type")
+        elif type_string == "FLOAT":
+            self.serialize = float_to_avro
+        elif type_string == "DOUBLE":
+            self.serialize = double_to_avro
+        elif type_string == "BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        elif type_string == "FIXED_LEN_BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        else:
+            raise AssertionError(f"Unknown physical type {type_string}")
+
+    def add_min(self, val: bytes) -> None:
+        if not self.current_min:
+            self.current_min = val
+        elif val < self.current_min:
+            self.current_min = val
+
+    def add_max(self, val: bytes) -> None:
+        if not self.current_max:
+            self.current_max = val
+        elif self.current_max < val:
+            self.current_max = val
+
+    def get_min(self) -> bytes:
+        return self.serialize(self.current_min)[:BOUND_TRUNCATED_LENGHT]
+
+    def get_max(self) -> bytes:
+        return self.serialize(self.current_max)[:BOUND_TRUNCATED_LENGHT]
+
+
+def fill_parquet_file_metadata(
+    df: DataFile, metadata: pq.FileMetaData, col_path_2_iceberg_id: Dict[str, 
int], file_size: int
+) -> None:
+    """
+    Computes and fills the following fields of the DataFile object.
+
+    - file_format
+    - record_count
+    - file_size_in_bytes
+    - column_sizes
+    - value_counts
+    - null_value_counts
+    - nan_value_counts
+    - lower_bounds
+    - upper_bounds
+    - split_offsets
+
+    Args:
+        df (DataFile): A DataFile object representing the Parquet file for 
which metadata is to be filled.
+        metadata (pyarrow.parquet.FileMetaData): A pyarrow metadata object.
+        col_path_2_iceberg_id: A mapping of column paths as in the 
`path_in_schema` attribute of the colum

Review Comment:
   A suggestion. Since we have the Iceberg write schema, we could also easily 
construct a `List[int, int]` that will tell the mapping of position to 
field-id. We have the `PreOrderSchemaVisitor` where we traverse the schema in 
order to construct this list. I don't like the `key_value` specific to PyArrow, 
and the list will be faster. WDYT?



##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16
+
+# Serialization rules: 
https://iceberg.apache.org/spec/#binary-single-value-serialization
+#
+# Type      Binary serialization
+# boolean   0x00 for false, non-zero byte for true
+# int       Stored as 4-byte little-endian
+# long      Stored as 8-byte little-endian
+# float     Stored as 4-byte little-endian
+# double    Stored as 8-byte little-endian
+# date      Stores days from the 1970-01-01 in an 4-byte little-endian int
+# time      Stores microseconds from midnight in an 8-byte little-endian long
+# timestamp without zone       Stores microseconds from 1970-01-01 
00:00:00.000000 in an 8-byte little-endian long
+# timestamp with zone  Stores microseconds from 1970-01-01 00:00:00.000000 UTC 
in an 8-byte little-endian long
+# string    UTF-8 bytes (without length)
+# uuid      16-byte big-endian value, see example in Appendix B
+# fixed(L)  Binary value
+# binary    Binary value (without length)
+#
+
+
+def bool_to_avro(value: bool) -> bytes:
+    return struct.pack("?", value)
+
+
+def int32_to_avro(value: int) -> bytes:
+    return struct.pack("<i", value)
+
+
+def int64_to_avro(value: int) -> bytes:
+    return struct.pack("<q", value)
+
+
+def float_to_avro(value: float) -> bytes:
+    return struct.pack("<f", value)
+
+
+def double_to_avro(value: float) -> bytes:
+    return struct.pack("<d", value)
+
+
+def bytes_to_avro(value: Union[bytes, str]) -> bytes:
+    if type(value) == str:
+        return value.encode()
+    else:
+        assert isinstance(value, bytes)  # appeases mypy
+        return value
+
+
+class StatsAggregator:
+    def __init__(self, type_string: str):

Review Comment:
   Why are we using a `type_string` here? The PyIceberg `PrimitiveType` seems 
to do the trick for me. We have methods for converting a PyArrow type to an 
IcebergType.
   
   Nit:
   ```suggestion
       def __init__(self, type_string: str) -> None:
   ```



##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16
+
+# Serialization rules: 
https://iceberg.apache.org/spec/#binary-single-value-serialization
+#
+# Type      Binary serialization
+# boolean   0x00 for false, non-zero byte for true
+# int       Stored as 4-byte little-endian
+# long      Stored as 8-byte little-endian
+# float     Stored as 4-byte little-endian
+# double    Stored as 8-byte little-endian
+# date      Stores days from the 1970-01-01 in an 4-byte little-endian int
+# time      Stores microseconds from midnight in an 8-byte little-endian long
+# timestamp without zone       Stores microseconds from 1970-01-01 
00:00:00.000000 in an 8-byte little-endian long
+# timestamp with zone  Stores microseconds from 1970-01-01 00:00:00.000000 UTC 
in an 8-byte little-endian long
+# string    UTF-8 bytes (without length)
+# uuid      16-byte big-endian value, see example in Appendix B
+# fixed(L)  Binary value
+# binary    Binary value (without length)
+#
+
+
+def bool_to_avro(value: bool) -> bytes:
+    return struct.pack("?", value)
+
+
+def int32_to_avro(value: int) -> bytes:
+    return struct.pack("<i", value)
+
+
+def int64_to_avro(value: int) -> bytes:
+    return struct.pack("<q", value)
+
+
+def float_to_avro(value: float) -> bytes:
+    return struct.pack("<f", value)
+
+
+def double_to_avro(value: float) -> bytes:
+    return struct.pack("<d", value)
+
+
+def bytes_to_avro(value: Union[bytes, str]) -> bytes:
+    if type(value) == str:
+        return value.encode()
+    else:
+        assert isinstance(value, bytes)  # appeases mypy
+        return value
+
+
+class StatsAggregator:
+    def __init__(self, type_string: str):
+        self.current_min: Any = None
+        self.current_max: Any = None
+        self.serialize: Any = None
+
+        if type_string == "BOOLEAN":
+            self.serialize = bool_to_avro
+        elif type_string == "INT32":
+            self.serialize = int32_to_avro
+        elif type_string == "INT64":
+            self.serialize = int64_to_avro
+        elif type_string == "INT96":
+            raise NotImplementedError("Statistics not implemented for INT96 
physical type")
+        elif type_string == "FLOAT":
+            self.serialize = float_to_avro
+        elif type_string == "DOUBLE":
+            self.serialize = double_to_avro
+        elif type_string == "BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        elif type_string == "FIXED_LEN_BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        else:
+            raise AssertionError(f"Unknown physical type {type_string}")
+
+    def add_min(self, val: bytes) -> None:
+        if not self.current_min:
+            self.current_min = val
+        elif val < self.current_min:

Review Comment:
   Any reason to not use Python's build in `min` function? That one might be 
passed down to C.



##########
python/pyiceberg/utils/file_stats.py:
##########
@@ -0,0 +1,333 @@
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing,
+#  software distributed under the License is distributed on an
+#  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+#  KIND, either express or implied.  See the License for the
+#  specific language governing permissions and limitations
+#  under the License.
+
+import struct
+from typing import (
+    Any,
+    Dict,
+    List,
+    Union,
+)
+
+import pyarrow.lib
+import pyarrow.parquet as pq
+
+from pyiceberg.manifest import DataFile, FileFormat
+from pyiceberg.schema import Schema, SchemaVisitor, visit
+from pyiceberg.types import (
+    IcebergType,
+    ListType,
+    MapType,
+    NestedField,
+    PrimitiveType,
+    StructType,
+)
+
+BOUND_TRUNCATED_LENGHT = 16
+
+# Serialization rules: 
https://iceberg.apache.org/spec/#binary-single-value-serialization
+#
+# Type      Binary serialization
+# boolean   0x00 for false, non-zero byte for true
+# int       Stored as 4-byte little-endian
+# long      Stored as 8-byte little-endian
+# float     Stored as 4-byte little-endian
+# double    Stored as 8-byte little-endian
+# date      Stores days from the 1970-01-01 in an 4-byte little-endian int
+# time      Stores microseconds from midnight in an 8-byte little-endian long
+# timestamp without zone       Stores microseconds from 1970-01-01 
00:00:00.000000 in an 8-byte little-endian long
+# timestamp with zone  Stores microseconds from 1970-01-01 00:00:00.000000 UTC 
in an 8-byte little-endian long
+# string    UTF-8 bytes (without length)
+# uuid      16-byte big-endian value, see example in Appendix B
+# fixed(L)  Binary value
+# binary    Binary value (without length)
+#
+
+
+def bool_to_avro(value: bool) -> bytes:
+    return struct.pack("?", value)
+
+
+def int32_to_avro(value: int) -> bytes:
+    return struct.pack("<i", value)
+
+
+def int64_to_avro(value: int) -> bytes:
+    return struct.pack("<q", value)
+
+
+def float_to_avro(value: float) -> bytes:
+    return struct.pack("<f", value)
+
+
+def double_to_avro(value: float) -> bytes:
+    return struct.pack("<d", value)
+
+
+def bytes_to_avro(value: Union[bytes, str]) -> bytes:
+    if type(value) == str:
+        return value.encode()
+    else:
+        assert isinstance(value, bytes)  # appeases mypy
+        return value
+
+
+class StatsAggregator:
+    def __init__(self, type_string: str):
+        self.current_min: Any = None
+        self.current_max: Any = None
+        self.serialize: Any = None
+
+        if type_string == "BOOLEAN":
+            self.serialize = bool_to_avro
+        elif type_string == "INT32":
+            self.serialize = int32_to_avro
+        elif type_string == "INT64":
+            self.serialize = int64_to_avro
+        elif type_string == "INT96":
+            raise NotImplementedError("Statistics not implemented for INT96 
physical type")
+        elif type_string == "FLOAT":
+            self.serialize = float_to_avro
+        elif type_string == "DOUBLE":
+            self.serialize = double_to_avro
+        elif type_string == "BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        elif type_string == "FIXED_LEN_BYTE_ARRAY":
+            self.serialize = bytes_to_avro
+        else:
+            raise AssertionError(f"Unknown physical type {type_string}")
+
+    def add_min(self, val: bytes) -> None:
+        if not self.current_min:

Review Comment:
   ```suggestion
           if self.current_min is not None:
   ```



-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: [email protected]

For queries about this service, please contact Infrastructure at:
[email protected]


---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]


Reply via email to