JingsongLi commented on code in PR #9148:
URL: https://github.com/apache/paimon/pull/9148#discussion_r3771892660


##########
paimon-python/pypaimon/read/reader/blob_view_read_support.py:
##########
@@ -0,0 +1,53 @@
+# 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.
+
+"""Helpers for eager blob-view/descriptor inline conversion on read."""
+
+from typing import List
+
+from pypaimon.common.options.core_options import CoreOptions
+from pypaimon.read.reader.iface.record_reader import RecordReader
+from pypaimon.schema.data_types import DataField, PyarrowFieldParser
+
+
+def needs_blob_inline_convert(table) -> bool:
+    return (
+        (CoreOptions.blob_view_fields(table.options)
+         and CoreOptions.blob_view_resolve_enabled(table.options))
+        or (not CoreOptions.blob_as_descriptor(table.options)
+            and CoreOptions.blob_descriptor_fields(table.options))
+    )
+
+
+def wrap_record_reader_with_blob_inline_convert(
+        reader: RecordReader,
+        split_read,
+        read_fields: List[DataField],
+) -> RecordReader:
+    from pypaimon.read.reader.auth_masking_reader import (
+        BatchToRecordReaderAdapter, RecordReaderToBatchAdapter)
+    from pypaimon.read.reader.blob_descriptor_convert_reader import 
BlobInlineConvertReader
+
+    schema = PyarrowFieldParser.from_paimon_schema(read_fields)
+    batch_reader = RecordReaderToBatchAdapter(reader, schema)
+    batch_reader = BlobInlineConvertReader(
+        batch_reader,
+        split_read.table,
+        prescan_reader_factory=lambda names: 
split_read._create_blob_view_prescan_reader(names),
+        blob_parallelism=split_read._blob_parallelism,
+    )
+    return BatchToRecordReaderAdapter(batch_reader)

Review Comment:
   [P1] Please preserve the typed field metadata when converting this batch 
reader back to rows. `BatchToRecordReaderAdapter._ArrowBatchIterator` currently 
creates each `OffsetRow` without `file_io`, BLOB/descriptor/vector indices, or 
the view lookup. On this new `MergeFileSplitRead` bridge, a valid 
descriptor/view BLOB is materialized, but `to_iterator()` consumers then get 
`TypeError: Field ... is not a BLOB field` from `row.get_blob(pos)`. This is 
reachable for Java-created primary-key BLOB tables. Please propagate the 
converted reader metadata into every `OffsetRow` and add a merge-read 
`to_iterator() + get_blob()` regression test.



##########
paimon-python/pypaimon/read/split_read.py:
##########
@@ -1003,6 +1047,23 @@ def _build_merge_function(self):
             value_field_names=[f.name for f in self.value_fields],
         )
 
+    def _create_blob_view_prescan_reader(self, field_names: set):
+        value_fields = self.read_fields[-self.value_arity:]
+        prescan_fields = [f for f in value_fields if f.name in field_names]
+        if not prescan_fields:
+            return EmptyFileRecordReader()

Review Comment:
   [P1] Please return an `EmptyRecordBatchReader` here. 
`BlobInlineConvertReader` unconditionally calls `read_arrow_batch()` on its 
prescan reader, while `EmptyFileRecordReader` only implements `read_batch()`. 
When a BLOB-view table is read through this merge path with a projection that 
excludes every configured view field, `prescan_fields` is empty and the query 
fails because the returned reader has no `read_arrow_batch()` method. Please 
add a projection regression test for that case.



##########
paimon-python/pypaimon/write/blob_format_writer.py:
##########
@@ -290,17 +290,38 @@ def _write_blob_data(self, blob_value: Blob, crc32: int):
             data = blob_value.to_data()
             crc32 = self._write_with_crc(data, crc32)
         else:
+            expected_length = None
+            if type(blob_value) is BlobRef:
+                descriptor_length = blob_value.to_descriptor().length
+                if descriptor_length >= 0:
+                    expected_length = descriptor_length
             stream = blob_value.new_input_stream()
             try:
-                chunk = stream.read(self.copy_buffer_size)
-                while chunk:
-                    crc32 = self._write_with_crc(chunk, crc32)
+                if expected_length is not None:
+                    crc32 = self._copy_exactly(stream, expected_length, crc32)
+                else:
                     chunk = stream.read(self.copy_buffer_size)
+                    while chunk:
+                        crc32 = self._write_with_crc(chunk, crc32)
+                        chunk = stream.read(self.copy_buffer_size)
             finally:
                 stream.close()

Review Comment:
   [P2] Please preserve the truncation `EOFError` when closing the source 
stream also fails. If a known-length descriptor expects 10 bytes, the source 
ends after 3, and a remote/native stream `close()` raises, this `finally` block 
replaces the useful `EOFError` with the close exception; `OffsetInputStream` 
can then attempt a second close during destruction. Please retain the copy/read 
exception while best-effort closing, and surface the close error only when 
copying succeeded. A short, close-failing source test would cover this failure 
path.



##########
paimon-python/pypaimon/table/row/offset_row.py:
##########
@@ -55,12 +62,57 @@ def get_field(self, pos: int):
             raise IndexError(f"Position {pos} is out of bounds for row arity 
{self.arity}")
         return self.row_tuple[self.offset + pos]
 
-    def get_blob(self, pos: int):
+    @staticmethod
+    def _normalize_blob_bytes(value):
+        if value is None:
+            return None
+        if hasattr(value, 'as_py'):
+            value = value.as_py()
+        if isinstance(value, str):
+            value = value.encode('utf-8')
+        if isinstance(value, bytearray):
+            value = bytes(value)
+        return value
+
+    def _resolve_blob_view_struct(self, view_struct):
         from pypaimon.table.row.blob import Blob
 
+        if self._blob_view_lookup is not None:
+            if self._blob_view_lookup.resolve_to_null(view_struct):
+                return None
+            descriptor = self._blob_view_lookup.resolve_descriptor(view_struct)
+            uri_reader = self._blob_view_lookup.resolve_uri_reader(view_struct)
+            return Blob.from_descriptor(uri_reader, descriptor)
+        return Blob.from_view(view_struct)
+
+    def _blob_from_descriptor_field_bytes(self, raw: bytes):
+        from pypaimon.table.row.blob import Blob, BlobDescriptor
+
+        if BlobDescriptor.is_blob_descriptor(raw):
+            return Blob.from_descriptor_bytes(raw, self._file_io)
+        if BlobDescriptor.parse_if_serialized(raw) is not None:
+            return Blob.from_descriptor_bytes(raw, self._file_io)
+        try:
+            # Accept v1/v2 descriptors with trailing padding (Java 
deserialize).
+            return Blob.from_descriptor_bytes(raw, self._file_io)
+        except ValueError:

Review Comment:
   [P2] Please do not downgrade descriptor parsing failures to `BlobData` here. 
Membership in `descriptor_field_indices` already establishes that the 
schema/storage context requires a descriptor. With this fallback, a truncated 
v1 descriptor or corrupted/future v2 descriptor is silently returned as raw 
payload by the row API, while `BlobInlineConvertReader` raises `ValueError` for 
the same bytes. This contradicts the PR stated fail-fast behavior and makes row 
and batch reads inconsistent. Materialized payloads are already represented by 
clearing the descriptor indices in `BlobInlineConvertReader`, so 
descriptor-indexed values should use `from_descriptor_bytes` strictly.



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