klion26 commented on code in PR #8392:
URL: https://github.com/apache/arrow-rs/pull/8392#discussion_r2366902225
##########
parquet-variant-compute/src/variant_array.rs:
##########
@@ -18,36 +18,194 @@
//! [`VariantArray`] implementation
use crate::type_conversion::primitive_conversion_single_value;
-use arrow::array::{Array, ArrayData, ArrayRef, AsArray, BinaryViewArray,
StructArray};
+use arrow::array::{Array, ArrayRef, AsArray, BinaryViewArray, StructArray};
use arrow::buffer::NullBuffer;
+use arrow::compute::cast;
use arrow::datatypes::{
Float16Type, Float32Type, Float64Type, Int16Type, Int32Type, Int64Type,
Int8Type, UInt16Type,
UInt32Type, UInt64Type, UInt8Type,
};
+use arrow_schema::extension::ExtensionType;
use arrow_schema::{ArrowError, DataType, Field, FieldRef, Fields};
use parquet_variant::Uuid;
use parquet_variant::Variant;
-use std::any::Any;
use std::sync::Arc;
+/// Arrow Variant [`ExtensionType`].
+///
+/// Represents the canonical Arrow Extension Type for storing variants.
+/// See [`VariantArray`] for more examples of using this extension type.
+pub struct VariantType;
+
+impl ExtensionType for VariantType {
+ const NAME: &'static str = "parquet.variant";
+
+ // Variants have no extension metadata
+ type Metadata = ();
+
+ fn metadata(&self) -> &Self::Metadata {
+ &()
+ }
+
+ fn serialize_metadata(&self) -> Option<String> {
+ None
+ }
+
+ fn deserialize_metadata(_metadata: Option<&str>) -> Result<Self::Metadata,
ArrowError> {
+ Ok(())
+ }
+
+ fn supports_data_type(&self, data_type: &DataType) -> Result<(),
ArrowError> {
+ // Note don't check for metadata/value fields here because they may be
+ // absent in shredded variants
+ if matches!(data_type, DataType::Struct(_)) {
+ Ok(())
+ } else {
+ Err(ArrowError::InvalidArgumentError(format!(
+ "VariantType only supports StructArray, got {}",
+ data_type
+ )))
+ }
+ }
+
+ fn try_new(data_type: &DataType, _metadata: Self::Metadata) ->
Result<Self, ArrowError> {
+ let new_self = Self;
+ new_self.supports_data_type(data_type)?;
+ Ok(new_self)
+ }
+}
+
/// An array of Parquet [`Variant`] values
///
Review Comment:
The doc here is very helpful!
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