delta_kernel 0.3.1

Core crate providing a Delta/Deltalake implementation focused on interoperability with a wide range of query engines.
Documentation 
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use arrow_array::{
    types::{GenericStringType, Int32Type, Int64Type},
    Array, BooleanArray, GenericByteArray, GenericListArray, MapArray, OffsetSizeTrait,
    PrimitiveArray,
};

use crate::{
    engine_data::{GetData, ListItem, MapItem},
    DeltaResult,
};

// actual impls (todo: could macro these)

impl<'a> GetData<'a> for BooleanArray {
    fn get_bool(&self, row_index: usize, _field_name: &str) -> DeltaResult<Option<bool>> {
        if self.is_valid(row_index) {
            Ok(Some(self.value(row_index)))
        } else {
            Ok(None)
        }
    }
}

impl<'a> GetData<'a> for PrimitiveArray<Int32Type> {
    fn get_int(&self, row_index: usize, _field_name: &str) -> DeltaResult<Option<i32>> {
        if self.is_valid(row_index) {
            Ok(Some(self.value(row_index)))
        } else {
            Ok(None)
        }
    }
}

impl<'a> GetData<'a> for PrimitiveArray<Int64Type> {
    fn get_long(&self, row_index: usize, _field_name: &str) -> DeltaResult<Option<i64>> {
        if self.is_valid(row_index) {
            Ok(Some(self.value(row_index)))
        } else {
            Ok(None)
        }
    }
}

impl<'a> GetData<'a> for GenericByteArray<GenericStringType<i32>> {
    fn get_str(&'a self, row_index: usize, _field_name: &str) -> DeltaResult<Option<&'a str>> {
        if self.is_valid(row_index) {
            Ok(Some(self.value(row_index)))
        } else {
            Ok(None)
        }
    }
}

impl<'a, OffsetSize> GetData<'a> for GenericListArray<OffsetSize>
where
    OffsetSize: OffsetSizeTrait,
{
    fn get_list(
        &'a self,
        row_index: usize,
        _field_name: &str,
    ) -> DeltaResult<Option<ListItem<'a>>> {
        if self.is_valid(row_index) {
            Ok(Some(ListItem::new(self, row_index)))
        } else {
            Ok(None)
        }
    }
}

impl<'a> GetData<'a> for MapArray {
    fn get_map(&'a self, row_index: usize, _field_name: &str) -> DeltaResult<Option<MapItem<'a>>> {
        if self.is_valid(row_index) {
            Ok(Some(MapItem::new(self, row_index)))
        } else {
            Ok(None)
        }
    }
}

macro_rules! impl_null_get {
    ( $(($name: ident, $typ: ty)), * ) => {
        $(
            fn $name(&'a self, _row_index: usize, _field_name: &str) -> DeltaResult<Option<$typ>> {
                Ok(None)
            }
        )*
    };
}

impl<'a> GetData<'a> for () {
    impl_null_get!(
        (get_bool, bool),
        (get_int, i32),
        (get_long, i64),
        (get_str, &'a str),
        (get_list, ListItem<'a>),
        (get_map, MapItem<'a>)
    );
}