klion26 commented on code in PR #8516:
URL: https://github.com/apache/arrow-rs/pull/8516#discussion_r2405000304
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parquet-variant-compute/src/type_conversion.rs:
##########
@@ -38,12 +38,33 @@ pub(crate) trait PrimitiveFromVariant: ArrowPrimitiveType {
fn from_variant(variant: &Variant<'_, '_>) -> Option<Self::Native>;
}
+/// Extension trait for Arrow timestamp types that can extract their native
value from a Variant
+/// We can't use [`PrimitiveFromVariant`] directly because we might need to
use methods that
+/// are only available on [`ArrowTimestampType`] (such as with_timezone_opt)
+pub(crate) trait TimestampFromVariant: ArrowTimestampType {
+ fn from_variant(variant: &Variant<'_, '_>) -> Option<Self::Native>;
+}
+
/// Macro to generate PrimitiveFromVariant implementations for Arrow primitive
types
macro_rules! impl_primitive_from_variant {
- ($arrow_type:ty, $variant_method:ident) => {
+ ($arrow_type:ty, $variant_method:ident $(, $cast_fn:expr)?) => {
impl PrimitiveFromVariant for $arrow_type {
fn from_variant(variant: &Variant<'_, '_>) -> Option<Self::Native>
{
- variant.$variant_method()
+ let value = variant.$variant_method();
+ $( let value = value.map($cast_fn); )?
+ value
+ }
+ }
+ };
+ ($arrow_type:ty, $( $variant_type:pat => $variant_method:ident,
$cast_fn:expr ),+ $(,)?) => {
+ impl TimestampFromVariant for $arrow_type {
+ fn from_variant(variant: &Variant<'_, '_>) -> Option<Self::Native>
{
+ match variant {
+ $(
+ $variant_type =>
variant.$variant_method().map($cast_fn),
+ )+
+ _ => None
+ }
Review Comment:
Ah, we can't treat the return value as the *physically* stored value, the
Enum Variant contains
`TimestampMicros/TimestampNtzMicros/TimestampNanos/TimestampNtzNanos`, they
contains `NaiveDatetime/DateTime<Utc>`, if we return the underlying pyysically
stored value, it will confuse the caller of these functions.
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