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github-merge-queue[bot] pushed a commit to branch 
gh-readonly-queue/main/pr-11838-d9d2d1edf46b1265d9fea9770c5e86933dff4ce8
in repository https://gitbox.apache.org/repos/asf/arrow-rs.git

commit 7dcc1602c460e25a624fd4f095a786352808b884
Author: Hippolyte Barraud <[email protected]>
AuthorDate: Wed Oct 28 15:07:04 2026 +0000

    fix(parquet): validate Arrow writer shapes and map-key schemas (#11838)
    
    # Which issue does this PR close?
    
    <!--
    It is not necessary to raise an issue, but it is encouraged if it is a
    non-trivial
    enhancement/bug.
    
    If this PR relates to an existing issue, but does not fully resolve it,
    please change
    the wording below from "Closes #NNN" to "Relates to #NNN" or "Part of
    #NNN" to avoid
    false closing an issue.
    -->
    
    - Closes #11837
    - Contributes to #9731
    - Part of #11273
    
    # Rationale for this change
    
    <!--
    Why are you proposing this change? If this is already explained clearly
    in the
    issue then this section is not needed. Explaining clearly why changes
    are proposed
    helps reviewers understand your changes and offer better suggestions for
    fixes.
    
    Please try to explain the problem you are trying to solve in terms of
    the user-visible
    behavior, rather than the implementation.
    -->
    
    See #11837. Structural mismatches between the input batch, declared
    schemas, and column writers should produce descriptive errors rather
    than silently ignore columns or panic. Map-key schema constraints should
    also be enforced when an explicit Parquet schema bypasses
    Arrow-to-Parquet conversion.
    
    # What changes are included in this PR?
    
    <!--
    There is no need to duplicate the description in the issue here but it
    is
    sometimes worth providing a summary of the individual changes in this
    PR.
    -->
    
    Reject mismatches between batch columns, planned Parquet leaves,
    physical column writers, and CDC chunkers instead of silently truncating
    zipped iteration or panicking on missing writers.
    
    Derive per-field leaf ranges from the target Arrow schema and verify the
    Arrow/Parquet leaf counts when creating column writers. Check batch,
    writer, and chunker counts before updating row-group accounting, and
    validate each field's actual leaf count before dispatching its writes.
    Preserve compatible dense, dictionary, and run-end encoded
    representations.
    
    Validate map-key schemas when creating an Arrow writer, including when
    an explicitly supplied Parquet schema bypasses Arrow-to-Parquet
    conversion.
    
    # Are these changes tested?
    
    <!--
    We typically require tests for all PRs in order to:
    1. Prevent the code from being accidentally broken by subsequent changes
    2. Serve as another way to document the expected behavior of the code
    
    If tests are not included in your PR, please explain why (for example,
    are they
    covered by existing tests, if so identify these tests)?
    
    If this PR claims a performance improvement, please include evidence
    such as
    benchmark results.
    
    DO NOT simply paste a list of commands ran to verify the code; this is
    what our
    CI is for and it pollutes the PR. ONLY explain if testing was included
    with this
    PR, or why it wasn't.
    -->
    
    Add regression coverage for shape mismatches, invalid map-key schemas,
    and reachable versus masked or unreferenced map-key nulls. All tests
    passing.
    
    # Are there any significant user-facing changes?
    
    <!--
    Significant user-facing changes include:
    - Breaking public API change
    - Significant change to existing functionality (e.g. function returns
    something different)
    
    These need to be explicitly called out to ensure we have proper
    documentation if
    required and to ensure we follow proper semantic versioning.
    
    DO NOT restate the changes of this PR; if a bug was fixed and already
    explained
    above, we don't need this to be restated as a user-facing change.
    -->
    
    No public API changes. Invalid schema or column-count combinations that
    were previously accepted, silently ignored, or caused a panic now return
    descriptive errors.
    
    Signed-off-by: Hippolyte Barraud <[email protected]>
---
 parquet/src/arrow/arrow_writer/mod.rs | 398 ++++++++++++++++++++++++++++++++--
 1 file changed, 385 insertions(+), 13 deletions(-)

diff --git a/parquet/src/arrow/arrow_writer/mod.rs 
b/parquet/src/arrow/arrow_writer/mod.rs
index 4b03e72f42..257ec463c7 100644
--- a/parquet/src/arrow/arrow_writer/mod.rs
+++ b/parquet/src/arrow/arrow_writer/mod.rs
@@ -21,6 +21,7 @@ use crate::column::chunker::ContentDefinedChunker;
 
 use bytes::Bytes;
 use std::io::Write;
+use std::ops::Range;
 use std::slice::Iter;
 use std::sync::{Arc, Mutex};
 use std::vec::IntoIter;
@@ -32,7 +33,9 @@ use arrow_schema::{
     ArrowError, DataType as ArrowDataType, Field, IntervalUnit, SchemaRef, 
TimeUnit,
 };
 
-use super::schema::{add_encoded_arrow_schema_to_metadata, 
decimal_length_from_precision};
+use super::schema::{
+    add_encoded_arrow_schema_to_metadata, decimal_length_from_precision, 
validate_map_key_type,
+};
 
 use crate::arrow::ArrowSchemaConverter;
 use crate::arrow::arrow_writer::byte_array::ByteArrayEncoder;
@@ -245,6 +248,9 @@ impl<W: Write + Send> ArrowWriter<W> {
         arrow_schema: SchemaRef,
         options: ArrowWriterOptions,
     ) -> Result<Self> {
+        for field in arrow_schema.fields() {
+            validate_map_key_type(field.data_type())?;
+        }
         let mut props = options.properties;
 
         let schema = if let Some(parquet_schema) = options.schema_descr {
@@ -1253,6 +1259,20 @@ impl ArrowColumnWriter {
     }
 }
 
+fn arrow_leaf_ranges(schema: &SchemaRef) -> Result<Vec<Range<usize>>> {
+    let mut count = 0;
+    schema
+        .fields
+        .iter()
+        .map(|field| {
+            validate_map_key_type(field.data_type())?;
+            let start = count;
+            count += compute_leaves(field, 
&arrow_array::new_empty_array(field.data_type()))?.len();
+            Ok(start..count)
+        })
+        .collect()
+}
+
 /// Encodes [`RecordBatch`] to a parquet row group
 ///
 /// Note: this structure is created by [`ArrowRowGroupWriterFactory`] 
internally used to
@@ -1276,11 +1296,13 @@ impl ArrowRowGroupWriter {
     }
 
     fn write(&mut self, batch: &RecordBatch) -> Result<()> {
+        let ranges = self.validate_batch_shape(batch, None)?;
         self.buffered_rows += batch.num_rows();
-        let mut writers = self.writers.iter_mut();
-        for (field, column) in 
self.schema.fields().iter().zip(batch.columns()) {
-            for leaf in compute_leaves(field.as_ref(), column)? {
-                writers.next().unwrap().write(&leaf)?;
+        for (column_idx, (field, range)) in 
self.schema.fields.iter().zip(ranges).enumerate() {
+            let leaves = compute_leaves(field, batch.column(column_idx))?;
+            Self::validate_leaf_count(field, &range, leaves.len())?;
+            for (offset, leaf) in leaves.into_iter().enumerate() {
+                self.writers[range.start + offset].write(&leaf)?;
             }
         }
         Ok(())
@@ -1291,20 +1313,61 @@ impl ArrowRowGroupWriter {
         batch: &RecordBatch,
         chunkers: &mut [ContentDefinedChunker],
     ) -> Result<()> {
+        let ranges = self.validate_batch_shape(batch, Some(chunkers.len()))?;
         self.buffered_rows += batch.num_rows();
-        let mut writers = self.writers.iter_mut();
-        let mut chunkers = chunkers.iter_mut();
-        for (field, column) in 
self.schema.fields().iter().zip(batch.columns()) {
-            for leaf in compute_leaves(field.as_ref(), column)? {
-                writers
-                    .next()
-                    .unwrap()
-                    .write_with_chunker(&leaf, chunkers.next().unwrap())?;
+        for (column_idx, (field, range)) in 
self.schema.fields.iter().zip(ranges).enumerate() {
+            let leaves = compute_leaves(field, batch.column(column_idx))?;
+            Self::validate_leaf_count(field, &range, leaves.len())?;
+            for (offset, leaf) in leaves.into_iter().enumerate() {
+                let index = range.start + offset;
+                self.writers[index].write_with_chunker(&leaf, &mut 
chunkers[index])?;
             }
         }
         Ok(())
     }
 
+    fn validate_batch_shape(
+        &self,
+        batch: &RecordBatch,
+        chunker_count: Option<usize>,
+    ) -> Result<Vec<Range<usize>>> {
+        if batch.num_columns() != self.schema.fields.len() {
+            return Err(ParquetError::ArrowError(format!(
+                "Incompatible schema: writer has {} top-level fields but batch 
has {} columns",
+                self.schema.fields.len(),
+                batch.num_columns()
+            )));
+        }
+        let ranges = arrow_leaf_ranges(&self.schema)?;
+        let leaf_count = ranges.last().map_or(0, |r| r.end);
+        if self.writers.len() != leaf_count {
+            return Err(ParquetError::General(format!(
+                "Arrow row-group writer has {} column writers for {} planned 
leaves",
+                self.writers.len(),
+                leaf_count
+            )));
+        }
+        if let Some(actual) = chunker_count
+            && actual != leaf_count
+        {
+            return Err(ParquetError::General(format!(
+                "content-defined chunking has {actual} chunkers for 
{leaf_count} planned leaves"
+            )));
+        }
+        Ok(ranges)
+    }
+
+    fn validate_leaf_count(field: &Field, range: &Range<usize>, actual: usize) 
-> Result<()> {
+        let expected = range.len();
+        if actual != expected {
+            return Err(ParquetError::ArrowError(format!(
+                "Incompatible schema: field '{}' produced {actual} leaf 
columns but writer expects {expected}",
+                field.name()
+            )));
+        }
+        Ok(())
+    }
+
     /// Returns the estimated total encoded bytes for this row group
     fn get_estimated_total_bytes(&self) -> usize {
         self.writers
@@ -1371,6 +1434,15 @@ impl ArrowRowGroupWriterFactory {
 
     /// Create column writers for a new row group, with the given row group 
index
     pub fn create_column_writers(&self, row_group_index: usize) -> 
Result<Vec<ArrowColumnWriter>> {
+        let ranges = arrow_leaf_ranges(&self.arrow_schema)?;
+        let leaf_count = ranges.last().map_or(0, |r| r.end);
+        if leaf_count != self.schema.num_columns() {
+            return Err(ParquetError::General(format!(
+                "Arrow schema maps to {} leaf columns but Parquet schema has 
{}",
+                leaf_count,
+                self.schema.num_columns()
+            )));
+        }
         let mut writers = Vec::with_capacity(self.arrow_schema.fields.len());
         let mut leaves = self.schema.columns().iter();
         let column_factory = self.column_writer_factory(row_group_index);
@@ -3109,6 +3181,306 @@ mod tests {
         assert_eq!(decoded, vec![batch]);
     }
 
+    #[test]
+    fn arrow_writer_rejects_missing_or_extra_top_level_columns_cleanly() {
+        let one_field = Arc::new(Schema::new(vec![Field::new(
+            "a",
+            ArrowDataType::Int32,
+            false,
+        )]));
+        let two_fields = Arc::new(Schema::new(vec![
+            Field::new("a", ArrowDataType::Int32, false),
+            Field::new("b", ArrowDataType::Int32, false),
+        ]));
+        let one_column = RecordBatch::try_new(
+            Arc::clone(&one_field),
+            vec![Arc::new(Int32Array::from(vec![1]))],
+        )
+        .unwrap();
+        let two_columns = RecordBatch::try_new(
+            Arc::clone(&two_fields),
+            vec![
+                Arc::new(Int32Array::from(vec![1])),
+                Arc::new(Int32Array::from(vec![2])),
+            ],
+        )
+        .unwrap();
+
+        let mut writer = ArrowWriter::try_new(Vec::new(), 
Arc::clone(&two_fields), None).unwrap();
+        let err = writer.write(&one_column).unwrap_err();
+        assert!(
+            err.to_string()
+                .contains("writer has 2 top-level fields but batch has 1 
columns"),
+            "{err}"
+        );
+        assert_eq!(writer.in_progress_rows(), 0);
+
+        let mut writer = ArrowWriter::try_new(Vec::new(), 
Arc::clone(&one_field), None).unwrap();
+        let err = writer.write(&two_columns).unwrap_err();
+        assert!(
+            err.to_string()
+                .contains("writer has 1 top-level fields but batch has 2 
columns"),
+            "{err}"
+        );
+        assert_eq!(writer.in_progress_rows(), 0);
+    }
+
+    #[test]
+    fn arrow_row_group_factory_rejects_parquet_leaf_count_mismatch_cleanly() {
+        let one_field = Arc::new(Schema::new(vec![Field::new(
+            "a",
+            ArrowDataType::Int32,
+            false,
+        )]));
+        let two_fields = Arc::new(Schema::new(vec![
+            Field::new("a", ArrowDataType::Int32, false),
+            Field::new("b", ArrowDataType::Int32, false),
+        ]));
+        let parquet = ArrowSchemaConverter::new().convert(&one_field).unwrap();
+        let props = Arc::new(WriterProperties::default());
+        let file_writer =
+            SerializedFileWriter::new(Vec::new(), parquet.root_schema_ptr(), 
Arc::clone(&props))
+                .unwrap();
+
+        let factory = ArrowRowGroupWriterFactory::new(&file_writer, 
Arc::clone(&two_fields));
+        let Err(err) = factory.create_column_writers(0) else {
+            panic!("mismatched schemas should not create column writers")
+        };
+        assert!(
+            err.to_string()
+                .contains("Arrow schema maps to 2 leaf columns but Parquet 
schema has 1"),
+            "{err}"
+        );
+
+        let parquet = 
ArrowSchemaConverter::new().convert(&two_fields).unwrap();
+        let file_writer =
+            SerializedFileWriter::new(Vec::new(), parquet.root_schema_ptr(), 
props).unwrap();
+        let factory = ArrowRowGroupWriterFactory::new(&file_writer, one_field);
+        let Err(err) = factory.create_column_writers(0) else {
+            panic!("mismatched schemas should not create column writers")
+        };
+        assert!(
+            err.to_string()
+                .contains("Arrow schema maps to 1 leaf columns but Parquet 
schema has 2"),
+            "{err}"
+        );
+    }
+
+    #[test]
+    fn arrow_writer_required_map_keys_reject_only_reachable_nulls() {
+        let keys: ArrayRef = Arc::new(DictionaryArray::<Int32Type>::new(
+            Int32Array::from(vec![1, 0, 1]),
+            Arc::new(Int32Array::from(vec![None, Some(7)])),
+        ));
+        let values = Int32Array::from(vec![Some(10), Some(20), None]);
+        let fields = Fields::from(vec![
+            Field::new("key", keys.data_type().clone(), false),
+            Field::new("value", DataType::Int32, true),
+        ]);
+        assert!(
+            StructArray::try_new(
+                fields.clone(),
+                vec![keys.clone(), Arc::new(values.clone())],
+                None
+            )
+            .is_err()
+        );
+
+        // ArrayData validates physical nulls, not null dictionary values. This
+        // safe construction reaches the writer with a logically null map key.
+        let data = ArrayData::builder(DataType::Struct(fields))
+            .len(3)
+            .add_child_data(keys.to_data())
+            .add_child_data(values.to_data())
+            .build()
+            .unwrap();
+        data.validate_full().unwrap();
+        let entries = StructArray::from(data);
+        let entries_field = Arc::new(Field::new("entries", 
entries.data_type().clone(), false));
+        let offsets = OffsetBuffer::new(vec![0i32, 1, 2, 3].into());
+        let map = MapArray::try_new(
+            entries_field.clone(),
+            offsets.clone(),
+            entries.clone(),
+            None,
+            false,
+        )
+        .unwrap();
+        assert_eq!(map.keys().logical_null_count(), 1);
+        let masked = MapArray::try_new(
+            entries_field,
+            offsets,
+            entries,
+            Some(NullBuffer::from(vec![true, false, true])),
+            false,
+        )
+        .unwrap();
+        let writer_schema = Arc::new(Schema::new(vec![Field::new(
+            "map",
+            DataType::Map(
+                Arc::new(Field::new(
+                    "entries",
+                    DataType::Struct(
+                        vec![
+                            Field::new("key", DataType::Int32, false),
+                            Field::new("value", DataType::Int32, true),
+                        ]
+                        .into(),
+                    ),
+                    false,
+                )),
+                false,
+            ),
+            true,
+        )]));
+        for cdc in [false, true] {
+            let props = WriterProperties::builder()
+                .set_content_defined_chunking(cdc.then(Default::default))
+                .build();
+            for (array, expected_keys, expected_null_maps) in [
+                (map.clone(), None, 0),
+                (map.slice(0, 1), Some(1), 0),
+                (map.slice(2, 1), Some(1), 0),
+                (masked.clone(), Some(2), 1),
+            ] {
+                let schema = Arc::new(Schema::new(vec![Field::new(
+                    "map",
+                    array.data_type().clone(),
+                    true,
+                )]));
+                let batch = RecordBatch::try_new(schema, 
vec![Arc::new(array)]).unwrap();
+                let mut bytes = Vec::new();
+                let mut writer =
+                    ArrowWriter::try_new(&mut bytes, writer_schema.clone(), 
Some(props.clone()))
+                        .unwrap();
+                let result = writer.write(&batch);
+                let Some(expected_keys) = expected_keys else {
+                    let err = result.unwrap_err();
+                    assert!(
+                        err.to_string().contains("Found null")
+                            && err.to_string().contains("required field 
'key'"),
+                        "{err}"
+                    );
+                    continue;
+                };
+                result.unwrap();
+                writer.close().unwrap();
+                let actual = 
ParquetRecordBatchReader::try_new(Bytes::from(bytes), 1024)
+                    .unwrap()
+                    .next()
+                    .unwrap()
+                    .unwrap();
+                let actual = actual.column(0).as_map();
+                assert_eq!(actual.null_count(), expected_null_maps);
+                assert_eq!(
+                    
actual.keys().as_primitive::<Int32Type>().values().as_ref(),
+                    vec![7; expected_keys]
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn arrow_writer_rejects_nullable_map_key_schemas_early() {
+        let schema_with_key = |key| {
+            Arc::new(Schema::new(vec![Field::new(
+                "map",
+                DataType::Map(
+                    Arc::new(Field::new(
+                        "entries",
+                        DataType::Struct(
+                            vec![key, Field::new("value", DataType::Int32, 
true)].into(),
+                        ),
+                        false,
+                    )),
+                    false,
+                ),
+                true,
+            )]))
+        };
+        let required = schema_with_key(Field::new("key", DataType::Int32, 
false));
+        let parquet = ArrowSchemaConverter::new().convert(&required).unwrap();
+        let ree = DataType::RunEndEncoded(
+            Arc::new(Field::new("run_ends", DataType::Int32, false)),
+            Arc::new(Field::new("values", DataType::Int32, true)),
+        );
+        for key in [
+            Field::new("key", DataType::Int32, true),
+            Field::new("key", ree.clone(), false),
+            Field::new(
+                "key",
+                DataType::Dictionary(Box::new(DataType::Int8), Box::new(ree)),
+                false,
+            ),
+        ] {
+            let schema = schema_with_key(key);
+            for explicit_schema in [false, true] {
+                for skip_metadata in [false, true] {
+                    let mut options =
+                        
ArrowWriterOptions::new().with_skip_arrow_metadata(skip_metadata);
+                    if explicit_schema {
+                        options = options.with_parquet_schema(parquet.clone());
+                    }
+                    let mut bytes = Vec::new();
+                    let err =
+                        ArrowWriter::try_new_with_options(&mut bytes, 
schema.clone(), options)
+                            .unwrap_err();
+                    assert!(
+                        err.to_string()
+                            .contains("Map key field 'key' must be 
non-nullable"),
+                        "{err}"
+                    );
+                    assert!(
+                        bytes.is_empty(),
+                        "schema rejection must precede file initialization"
+                    );
+                }
+            }
+            let file = SerializedFileWriter::new(
+                Vec::new(),
+                parquet.root_schema_ptr(),
+                Arc::new(WriterProperties::default()),
+            )
+            .unwrap();
+            let factory = ArrowRowGroupWriterFactory::new(&file, schema);
+            let Err(err) = factory.create_column_writers(0) else {
+                panic!("nullable map-key schema should not create column 
writers")
+            };
+            assert!(
+                err.to_string()
+                    .contains("Map key field 'key' must be non-nullable"),
+                "{err}"
+            );
+        }
+    }
+
+    #[test]
+    fn 
eager_row_group_validation_rejects_writer_and_chunker_count_mismatches() {
+        let schema = Arc::new(Schema::new(vec![Field::new("a", 
DataType::Int32, false)]));
+        let batch = RecordBatch::try_new(schema.clone(), 
vec![Arc::new(Int32Array::from(vec![1]))])
+            .unwrap();
+        let writer = ArrowWriter::try_new(Vec::new(), schema, None).unwrap();
+        let (_file, factory) = writer.into_serialized_writer().unwrap();
+        let mut group = factory.create_row_group_writer(0).unwrap();
+        assert!(
+            group
+                .write_with_chunkers(&batch, &mut [])
+                .unwrap_err()
+                .to_string()
+                .contains("chunkers")
+        );
+        assert_eq!(group.buffered_rows, 0);
+        group.writers.clear();
+        assert!(
+            group
+                .write(&batch)
+                .unwrap_err()
+                .to_string()
+                .contains("column writers")
+        );
+        assert_eq!(group.buffered_rows, 0);
+    }
+
     #[test]
     fn arrow_writer_page_size() {
         let schema = Arc::new(Schema::new(vec![Field::new("col", 
DataType::Utf8, false)]));

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