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fix(arrow): use FULL nanoarrow validation in ProjectBatch #1043

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fix(arrow): use FULL nanoarrow validation in ProjectBatch #1043

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8 changes: 7 additions & 1 deletion src/iceberg/arrow_c_data_util.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -341,8 +341,14 @@ Result<ArrowArray> ProjectBatchNanoarrow(
internal::ArrowArrayViewGuard input_view_guard(&input_view);
ICEBERG_NANOARROW_RETURN_UNEXPECTED_WITH_ERROR(
ArrowArrayViewSetArray(&input_view, &input_batch, &error), error);
// FULL validation is required here: the append path below uses
// ArrowArrayViewGet{String,Bytes}Unsafe and raw list/map offset arithmetic,
// which nanoarrow only documents as memory-safe after FULL validation
// (DEFAULT does not check that every offsets-buffer entry is non-decreasing
// and in-bounds). This matches the FULL validation already performed on the
// equivalent untrusted-batch boundary in manifest_reader.cc.
ICEBERG_NANOARROW_RETURN_UNEXPECTED_WITH_ERROR(
ArrowArrayViewValidate(&input_view, NANOARROW_VALIDATION_LEVEL_DEFAULT, &error),
ArrowArrayViewValidate(&input_view, NANOARROW_VALIDATION_LEVEL_FULL, &error),

@shangxinli shangxinli Oct 20, 2026 •
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ProjectBatch runs per batch on the scan path via file_scan_task_reader.cc:118, so FULL validation now walks every offsets buffer on every batch. Unlike the manifest_reader case these come from our own readers - is that cost intended?

@gty404 gty404 Oct 21, 2026 •
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Good catch, the cost is real but small in absolute terms. I benchmarked ProjectBatch (nanoarrow path) on a 50k-row batch (int32 + string column) with DEFAULT vs FULL validation, averaged over 200 runs:

selectivity DEFAULT FULL overhead
100% rows alive ~4074 us/batch ~4219 us/batch +3.6%
1% rows alive (heavy delete filtering) ~44.5 us/batch ~82.2 us/batch +85% (~1.85x)

So in the worst case (most rows filtered out by deletes, which is exactly where the row-append cost no longer dominates), FULL validation roughly doubles this step's time - but the absolute delta is ~38us for a 50k-row batch (~0.75ns/row), which should be negligible next to I/O/decode for a real scan.

Given nanoarrow has no bounds-checked "safe" counterpart to ArrowArrayViewGetStringUnsafe/GetBytesUnsafe in this pinned version, FULL batch-level validation is the only way to satisfy contract today. @wgtmac curious for your take: keep this as-is given the cost is small and bounded, or is there a reason to treat the in-tree reader path differently (e.g. skip FULL validation when the batch is known to come from our own Avro/Parquet readers)?

error);

ArrowArray output_array;
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39 changes: 39 additions & 0 deletions src/iceberg/test/arrow_c_data_util_test.cc
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Expand Up @@ -20,6 +20,7 @@
/// \file arrow_c_data_util_test.cc
/// Verifies ProjectBatch behavior across registered implementations.

#include <array>
#include <cstdint>
#include <string_view>
#include <utility>
Expand Down Expand Up @@ -191,4 +192,42 @@ TEST(ProjectBatchTest, ProjectionRejectsNestedPruning) {
EXPECT_THAT(projection, IsError(ErrorKind::kInvalidArgument));
}

TEST(ProjectBatchTest, RejectsNonMonotonicStringOffsets) {
auto schema = std::make_shared<Schema>(
std::vector<SchemaField>{SchemaField::MakeRequired(1, "value", string())});

// Arrow's builders always emit monotonic offsets, so a batch with a
// corrupt offsets buffer has to be hand-assembled via the nanoarrow C ABI.
// offsets = [0, 5, 2] with a 2-byte data buffer: DEFAULT validation only
// checks the first (0) and last (2) offsets, both of which are consistent
// with the 2-byte buffer, so it accepts this array. FULL validation also
// walks the offsets buffer and rejects it because 2 < 5.
ArrowArray root;
ASSERT_EQ(ArrowArrayInitFromType(&root, NANOARROW_TYPE_STRUCT), NANOARROW_OK);
ASSERT_EQ(ArrowArrayAllocateChildren(&root, 1), NANOARROW_OK);

ArrowArray* value_array = root.children[0];
ASSERT_EQ(ArrowArrayInitFromType(value_array, NANOARROW_TYPE_STRING), NANOARROW_OK);
const std::array<int32_t, 3> raw_offsets = {0, 5, 2};
ASSERT_EQ(ArrowBufferAppend(ArrowArrayBuffer(value_array, 1), raw_offsets.data(),
raw_offsets.size() * sizeof(int32_t)),
NANOARROW_OK);
ASSERT_EQ(ArrowBufferAppend(ArrowArrayBuffer(value_array, 2), "ab", 2), NANOARROW_OK);
value_array->length = 2;
value_array->null_count = 0;
ASSERT_EQ(ArrowArrayFinishBuildingDefault(value_array, nullptr), NANOARROW_OK);

root.length = 2;
root.null_count = 0;
ASSERT_EQ(ArrowArrayFinishBuildingDefault(&root, nullptr), NANOARROW_OK);

auto projection = ProjectionContext::Make(*schema, *schema, nullptr);
ASSERT_THAT(projection, IsOk());

// No rows are selected, so the malformed offsets must be caught by batch
// validation itself rather than by appending the corrupt row.
auto result = ProjectBatch(&root, /*row_indices=*/{}, projection.value());
EXPECT_THAT(result, IsError(ErrorKind::kInvalidArrowData));
}

} // namespace iceberg::internal
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