idhash 0.3.0

Calculate a Row-Invariant ID for Tabular Data
Documentation 
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use fasthash::murmur3::hash128;
use std::sync::Arc;

use crate::{config::IdHashConfig, unf_vector::UNFVector, utils::ThreadArrayChunk};
use arrow::{
    array::{
        BooleanArray, Float32Array, Float64Array, Int32Array, Int64Array, UInt16Array, UInt32Array,
        UInt64Array, Utf8Array,
    },
    chunk::Chunk,
    datatypes::Schema,
};

use arrow::datatypes::TimeUnit;

struct HashIterator<T>(Vec<T>);

impl<T> Iterator for HashIterator<T>
where
    T: Iterator<Item = Vec<u8>>,
{
    type Item = Vec<Vec<u8>>;

    fn next(&mut self) -> Option<Self::Item> {
        self.0.iter_mut().map(Iterator::next).collect()
    }
}

fn convert_col_to_raw<'a>(
    col: &'a dyn std::any::Any,
    column_index: usize,
    schema: &Arc<Schema>,
    is_null: bool,
    config: IdHashConfig,
) -> Box<dyn Iterator<Item = Vec<u8>> + 'a> {
    match (*schema.fields)[column_index].data_type() {
        arrow::datatypes::DataType::Null => todo!(),
        arrow::datatypes::DataType::Boolean => col
            .downcast_ref::<BooleanArray>()
            .expect("Failed to downcast to Bool")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Int8 => col
            .downcast_ref::<Int32Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Int16 => col
            .downcast_ref::<Int32Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Int32 => col
            .downcast_ref::<Int32Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Int64 => col
            .downcast_ref::<Int64Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::UInt8 => col
            .downcast_ref::<UInt16Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::UInt16 => col
            .downcast_ref::<UInt16Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::UInt32 => col
            .downcast_ref::<UInt32Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::UInt64 => col
            .downcast_ref::<UInt64Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Float16 => col
            .downcast_ref::<Float32Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Float32 => col
            .downcast_ref::<Float32Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Float64 => col
            .downcast_ref::<Float64Array>()
            .expect("Failed to Downcast")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Timestamp(TimeUnit::Microsecond, _)
        | arrow::datatypes::DataType::Timestamp(TimeUnit::Millisecond, _)
        | arrow::datatypes::DataType::Timestamp(TimeUnit::Nanosecond, _)
        | arrow::datatypes::DataType::Timestamp(TimeUnit::Second, _) => col
            .downcast_ref::<Int64Array>()
            .expect("Failed to Downcast to Int64Array")
            .raw(12, config.digits, is_null),
        arrow::datatypes::DataType::Time32(_) => todo!(),
        arrow::datatypes::DataType::Time64(_) => todo!(),
        arrow::datatypes::DataType::Duration(_) => todo!(),
        arrow::datatypes::DataType::Interval(_) => todo!(),
        arrow::datatypes::DataType::Binary => todo!(),
        arrow::datatypes::DataType::FixedSizeBinary(_) => todo!(),
        arrow::datatypes::DataType::LargeBinary => todo!(),
        arrow::datatypes::DataType::List(_) => todo!(),
        arrow::datatypes::DataType::FixedSizeList(_, _) => todo!(),
        arrow::datatypes::DataType::LargeList(_) => todo!(),
        arrow::datatypes::DataType::Struct(_) => todo!(),
        arrow::datatypes::DataType::Union(_, _, _) => todo!(),
        arrow::datatypes::DataType::Dictionary(_, _, _) => todo!(),
        arrow::datatypes::DataType::Decimal(_, _) => todo!(),
        arrow::datatypes::DataType::Map(_, _) => todo!(),
        arrow::datatypes::DataType::Extension(_, _, _) => todo!(),
        arrow::datatypes::DataType::Date32 => col
            .downcast_ref::<Int32Array>()
            .expect("Failed to downcast Date to Int32")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Date64 => col
            .downcast_ref::<Int64Array>()
            .expect("Failed to downcast Date to Int64")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::Utf8 => col
            .downcast_ref::<Utf8Array<i32>>()
            .expect("Failed to downcast to Utf-8")
            .raw(config.characters, config.digits, is_null),
        arrow::datatypes::DataType::LargeUtf8 => todo!(),
    }
}

/// Produce MurmurHash for a given RecordBatch
///
pub(crate) fn idhash_batch(
    input: Chunk<ThreadArrayChunk>,
    schema: &Arc<Schema>,
    config: IdHashConfig,
) -> u128 {
    // To progress row-wise, collect all Columns into Iterators, then progress
    // each iterator one at a time.
    // https://stackoverflow.com/a/55292215
    HashIterator(
        input
            .columns()
            .iter()
            .enumerate()
            .map(|(col_index, col)| {
                convert_col_to_raw(
                    col.as_any(),
                    col_index,
                    schema,
                    col.null_count() > 0,
                    config,
                )
            })
            .collect(),
    )
    .map(|row| hash128(row.into_iter().flatten().collect::<Vec<u8>>()))
    .reduce(|acc, x| acc.wrapping_add(x))
    .unwrap()
}