Preserve bitmask (#1037)

arrow/src/array/builder.rs

@@ -419,6 +419,11 @@ impl BooleanBufferBuilder {
         );
     }
 
+    /// Returns the packed bits
+    pub fn as_slice(&self) -> &[u8] {
+        self.buffer.as_slice()
+    }
+
     #[inline]
     pub fn finish(&mut self) -> Buffer {
         let buf = std::mem::replace(&mut self.buffer, MutableBuffer::new(0));

parquet/benches/arrow_array_reader.rs

@@ -301,8 +301,13 @@ fn create_int32_primitive_array_reader(
     column_desc: ColumnDescPtr,
 ) -> impl ArrayReader {
     use parquet::arrow::array_reader::PrimitiveArrayReader;
-    PrimitiveArrayReader::<Int32Type>::new(Box::new(page_iterator), column_desc, None)
-        .unwrap()
+    PrimitiveArrayReader::<Int32Type>::new_with_options(
+        Box::new(page_iterator),
+        column_desc,
+        None,
+        true,
+    )
+    .unwrap()
 }
 
 fn create_string_arrow_array_reader(

parquet/src/arrow/array_reader.rs

@@ -247,6 +247,17 @@ where
         pages: Box<dyn PageIterator>,
         column_desc: ColumnDescPtr,
         arrow_type: Option<ArrowType>,
+    ) -> Result<Self> {
+        Self::new_with_options(pages, column_desc, arrow_type, false)
+    }
+
+    /// Construct primitive array reader with ability to only compute null mask and not
+    /// buffer level data
+    pub fn new_with_options(
+        pages: Box<dyn PageIterator>,
+        column_desc: ColumnDescPtr,
+        arrow_type: Option<ArrowType>,
+        null_mask_only: bool,
     ) -> Result<Self> {
         // Check if Arrow type is specified, else create it from Parquet type
         let data_type = match arrow_type {
@@ -256,7 +267,7 @@ where
                 .clone(),
         };
 
-        let record_reader = RecordReader::<T>::new(column_desc.clone());
+        let record_reader = RecordReader::<T>::new_with_options(column_desc.clone(), null_mask_only);
 
         Ok(Self {
             data_type,
@@ -1350,19 +1361,26 @@ impl<'a> TypeVisitor<Option<Box<dyn ArrayReader>>, &'a ArrayReaderBuilderContext
             let mut new_context = context.clone();
             new_context.path.append(vec![cur_type.name().to_string()]);
 
-            match cur_type.get_basic_info().repetition() {
+            let null_mask_only = match cur_type.get_basic_info().repetition() {
                 Repetition::REPEATED => {
                     new_context.def_level += 1;
                     new_context.rep_level += 1;
+                    false
                 }
                 Repetition::OPTIONAL => {
                     new_context.def_level += 1;
+
+                    // Can just compute null mask if no parent
+                    context.def_level == 0 && context.rep_level == 0
                 }
-                _ => (),
-            }
+                _ => false,
+            };
 
-            let reader =
-                self.build_for_primitive_type_inner(cur_type.clone(), &new_context)?;
+            let reader = self.build_for_primitive_type_inner(
+                cur_type.clone(),
+                &new_context,
+                null_mask_only,
+            )?;
 
             if cur_type.get_basic_info().repetition() == Repetition::REPEATED {
                 Err(ArrowError(
@@ -1641,6 +1659,7 @@ impl<'a> ArrayReaderBuilder {
         &self,
         cur_type: TypePtr,
         context: &'a ArrayReaderBuilderContext,
+        null_mask_only: bool,
     ) -> Result<Box<dyn ArrayReader>> {
         let column_desc = Arc::new(ColumnDescriptor::new(
             cur_type.clone(),
@@ -1658,30 +1677,39 @@ impl<'a> ArrayReaderBuilder {
             .map(|f| f.data_type().clone());
 
         match cur_type.get_physical_type() {
-            PhysicalType::BOOLEAN => Ok(Box::new(PrimitiveArrayReader::<BoolType>::new(
-                page_iterator,
-                column_desc,
-                arrow_type,
-            )?)),
+            PhysicalType::BOOLEAN => Ok(Box::new(
+                PrimitiveArrayReader::<BoolType>::new_with_options(
+                    page_iterator,
+                    column_desc,
+                    arrow_type,
+                    null_mask_only,
+                )?,
+            )),
             PhysicalType::INT32 => {
                 if let Some(ArrowType::Null) = arrow_type {
                     Ok(Box::new(NullArrayReader::<Int32Type>::new(
                         page_iterator,
                         column_desc,
                     )?))
                 } else {
-                    Ok(Box::new(PrimitiveArrayReader::<Int32Type>::new(
-                        page_iterator,
-                        column_desc,
-                        arrow_type,
-                    )?))
+                    Ok(Box::new(
+                        PrimitiveArrayReader::<Int32Type>::new_with_options(
+                            page_iterator,
+                            column_desc,
+                            arrow_type,
+                            null_mask_only,
+                        )?,
+                    ))
                 }
             }
-            PhysicalType::INT64 => Ok(Box::new(PrimitiveArrayReader::<Int64Type>::new(
-                page_iterator,
-                column_desc,
-                arrow_type,
-            )?)),
+            PhysicalType::INT64 => Ok(Box::new(
+                PrimitiveArrayReader::<Int64Type>::new_with_options(
+                    page_iterator,
+                    column_desc,
+                    arrow_type,
+                    null_mask_only,
+                )?,
+            )),
             PhysicalType::INT96 => {
                 // get the optional timezone information from arrow type
                 let timezone = arrow_type
@@ -1705,18 +1733,22 @@ impl<'a> ArrayReaderBuilder {
                     arrow_type,
                 )?))
             }
-            PhysicalType::FLOAT => Ok(Box::new(PrimitiveArrayReader::<FloatType>::new(
-                page_iterator,
-                column_desc,
-                arrow_type,
-            )?)),
-            PhysicalType::DOUBLE => {
-                Ok(Box::new(PrimitiveArrayReader::<DoubleType>::new(
+            PhysicalType::FLOAT => Ok(Box::new(
+                PrimitiveArrayReader::<FloatType>::new_with_options(
                     page_iterator,
                     column_desc,
                     arrow_type,
-                )?))
-            }
+                    null_mask_only,
+                )?,
+            )),
+            PhysicalType::DOUBLE => Ok(Box::new(
+                PrimitiveArrayReader::<DoubleType>::new_with_options(
+                    page_iterator,
+                    column_desc,
+                    arrow_type,
+                    null_mask_only,
+                )?,
+            )),
             PhysicalType::BYTE_ARRAY => {
                 if cur_type.get_basic_info().converted_type() == ConvertedType::UTF8 {
                     if let Some(ArrowType::LargeUtf8) = arrow_type {

parquet/src/arrow/record_reader.rs

@@ -73,9 +73,19 @@ where
     V: ValuesBuffer + Default,
     CV: ColumnValueDecoder<Slice = V::Slice>,
 {
+    /// Create a new [`GenericRecordReader`]
     pub fn new(desc: ColumnDescPtr) -> Self {
-        let def_levels =
-            (desc.max_def_level() > 0).then(|| DefinitionLevelBuffer::new(&desc));
+        Self::new_with_options(desc, false)
+    }
+
+    /// Create a new [`GenericRecordReader`] with the ability to only generate the bitmask
+    ///
+    /// If `null_mask_only` is true only the null bitmask will be generated and
+    /// [`Self::consume_def_levels`] and [`Self::consume_rep_levels`] will always return `None`
+    ///
+    pub(crate) fn new_with_options(desc: ColumnDescPtr, null_mask_only: bool) -> Self {
+        let def_levels = (desc.max_def_level() > 0)
+            .then(|| DefinitionLevelBuffer::new(&desc, null_mask_only));
 
         let rep_levels = (desc.max_rep_level() > 0).then(ScalarBuffer::new);
 
@@ -171,7 +181,7 @@ where
     /// as record values, e.g. those from `self.num_values` to `self.values_written`.
     pub fn consume_def_levels(&mut self) -> Result<Option<Buffer>> {
         Ok(match self.def_levels.as_mut() {
-            Some(x) => Some(x.split_off(self.num_values)),
+            Some(x) => x.split_levels(self.num_values),
             None => None,
         })
     }
@@ -221,10 +231,7 @@ where
             .as_mut()
             .map(|levels| levels.spare_capacity_mut(batch_size));
 
-        let def_levels = self
-            .def_levels
-            .as_mut()
-            .map(|levels| levels.spare_capacity_mut(batch_size));
+        let def_levels = self.def_levels.as_mut();
 
         let values = self.records.spare_capacity_mut(batch_size);
 

parquet/src/arrow/record_reader/buffer.rs

@@ -114,6 +114,12 @@ impl<T: ScalarValue> ScalarBuffer<T> {
         self.len == 0
     }
 
+    pub fn resize(&mut self, len: usize) {
+        self.buffer
+            .resize(len * std::mem::size_of::<T>(), 0);
+        self.len = len;
+    }
+
     #[inline]
     pub fn as_slice(&self) -> &[T] {
         let (prefix, buf, suffix) = unsafe { self.buffer.as_slice().align_to::<T>() };