datafusion_common/

hash_utils.rs

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

//! Functionality used both on logical and physical plans

use ahash::RandomState;
use arrow::array::types::{IntervalDayTime, IntervalMonthDayNano};
use arrow::array::*;
use arrow::datatypes::*;
#[cfg(not(feature = "force_hash_collisions"))]
use arrow::{downcast_dictionary_array, downcast_primitive_array};

#[cfg(not(feature = "force_hash_collisions"))]
use crate::cast::{
    as_binary_view_array, as_boolean_array, as_fixed_size_list_array,
    as_generic_binary_array, as_large_list_array, as_list_array, as_map_array,
    as_string_array, as_string_view_array, as_struct_array, as_union_array,
};
use crate::error::Result;
use crate::error::{_internal_datafusion_err, _internal_err};
use std::cell::RefCell;

// Combines two hashes into one hash
#[inline]
pub fn combine_hashes(l: u64, r: u64) -> u64 {
    let hash = (17 * 37u64).wrapping_add(l);
    hash.wrapping_mul(37).wrapping_add(r)
}

/// Maximum size for the thread-local hash buffer before truncation (4MB = 524,288 u64 elements).
/// The goal of this is to avoid unbounded memory growth that would appear as a memory leak.
/// We allow temporary allocations beyond this size, but after use the buffer is truncated
/// to this size.
const MAX_BUFFER_SIZE: usize = 524_288;

thread_local! {
    /// Thread-local buffer for hash computations to avoid repeated allocations.
    /// The buffer is reused across calls and truncated if it exceeds MAX_BUFFER_SIZE.
    /// Defaults to a capacity of 8192 u64 elements which is the default batch size.
    /// This corresponds to 64KB of memory.
    static HASH_BUFFER: RefCell<Vec<u64>> = const { RefCell::new(Vec::new()) };
}

/// Creates hashes for the given arrays using a thread-local buffer, then calls the provided callback
/// with an immutable reference to the computed hashes.
///
/// This function manages a thread-local buffer to avoid repeated allocations. The buffer is automatically
/// truncated if it exceeds `MAX_BUFFER_SIZE` after use.
///
/// # Arguments
/// * `arrays` - The arrays to hash (must contain at least one array)
/// * `random_state` - The random state for hashing
/// * `callback` - A function that receives an immutable reference to the hash slice and returns a result
///
/// # Errors
/// Returns an error if:
/// - No arrays are provided
/// - The function is called reentrantly (i.e., the callback invokes `with_hashes` again on the same thread)
/// - The function is called during or after thread destruction
///
/// # Example
/// ```ignore
/// use datafusion_common::hash_utils::{with_hashes, RandomState};
/// use arrow::array::{Int32Array, ArrayRef};
/// use std::sync::Arc;
///
/// let array: ArrayRef = Arc::new(Int32Array::from(vec![1, 2, 3]));
/// let random_state = RandomState::new();
///
/// let result = with_hashes([&array], &random_state, |hashes| {
///     // Use the hashes here
///     Ok(hashes.len())
/// })?;
/// ```
pub fn with_hashes<I, T, F, R>(
    arrays: I,
    random_state: &RandomState,
    callback: F,
) -> Result<R>
where
    I: IntoIterator<Item = T>,
    T: AsDynArray,
    F: FnOnce(&[u64]) -> Result<R>,
{
    // Peek at the first array to determine buffer size without fully collecting
    let mut iter = arrays.into_iter().peekable();

    // Get the required size from the first array
    let required_size = match iter.peek() {
        Some(arr) => arr.as_dyn_array().len(),
        None => return _internal_err!("with_hashes requires at least one array"),
    };

    HASH_BUFFER.try_with(|cell| {
        let mut buffer = cell.try_borrow_mut()
            .map_err(|_| _internal_datafusion_err!("with_hashes cannot be called reentrantly on the same thread"))?;

        // Ensure buffer has sufficient length, clearing old values
        buffer.clear();
        buffer.resize(required_size, 0);

        // Create hashes in the buffer - this consumes the iterator
        create_hashes(iter, random_state, &mut buffer[..required_size])?;

        // Execute the callback with an immutable slice
        let result = callback(&buffer[..required_size])?;

        // Cleanup: truncate if buffer grew too large
        if buffer.capacity() > MAX_BUFFER_SIZE {
            buffer.truncate(MAX_BUFFER_SIZE);
            buffer.shrink_to_fit();
        }

        Ok(result)
    }).map_err(|_| _internal_datafusion_err!("with_hashes cannot access thread-local storage during or after thread destruction"))?
}

#[cfg(not(feature = "force_hash_collisions"))]
fn hash_null(random_state: &RandomState, hashes_buffer: &'_ mut [u64], mul_col: bool) {
    if mul_col {
        hashes_buffer.iter_mut().for_each(|hash| {
            // stable hash for null value
            *hash = combine_hashes(random_state.hash_one(1), *hash);
        })
    } else {
        hashes_buffer.iter_mut().for_each(|hash| {
            *hash = random_state.hash_one(1);
        })
    }
}

pub trait HashValue {
    fn hash_one(&self, state: &RandomState) -> u64;
}

impl<T: HashValue + ?Sized> HashValue for &T {
    fn hash_one(&self, state: &RandomState) -> u64 {
        T::hash_one(self, state)
    }
}

macro_rules! hash_value {
    ($($t:ty),+) => {
        $(impl HashValue for $t {
            fn hash_one(&self, state: &RandomState) -> u64 {
                state.hash_one(self)
            }
        })+
    };
}
hash_value!(i8, i16, i32, i64, i128, i256, u8, u16, u32, u64, u128);
hash_value!(bool, str, [u8], IntervalDayTime, IntervalMonthDayNano);

macro_rules! hash_float_value {
    ($(($t:ty, $i:ty)),+) => {
        $(impl HashValue for $t {
            fn hash_one(&self, state: &RandomState) -> u64 {
                state.hash_one(<$i>::from_ne_bytes(self.to_ne_bytes()))
            }
        })+
    };
}
hash_float_value!((half::f16, u16), (f32, u32), (f64, u64));

/// Builds hash values of PrimitiveArray and writes them into `hashes_buffer`
/// If `rehash==true` this combines the previous hash value in the buffer
/// with the new hash using `combine_hashes`
#[cfg(not(feature = "force_hash_collisions"))]
fn hash_array_primitive<T>(
    array: &PrimitiveArray<T>,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
    rehash: bool,
) where
    T: ArrowPrimitiveType<Native: HashValue>,
{
    assert_eq!(
        hashes_buffer.len(),
        array.len(),
        "hashes_buffer and array should be of equal length"
    );

    if array.null_count() == 0 {
        if rehash {
            for (hash, &value) in hashes_buffer.iter_mut().zip(array.values().iter()) {
                *hash = combine_hashes(value.hash_one(random_state), *hash);
            }
        } else {
            for (hash, &value) in hashes_buffer.iter_mut().zip(array.values().iter()) {
                *hash = value.hash_one(random_state);
            }
        }
    } else if rehash {
        for (i, hash) in hashes_buffer.iter_mut().enumerate() {
            if !array.is_null(i) {
                let value = unsafe { array.value_unchecked(i) };
                *hash = combine_hashes(value.hash_one(random_state), *hash);
            }
        }
    } else {
        for (i, hash) in hashes_buffer.iter_mut().enumerate() {
            if !array.is_null(i) {
                let value = unsafe { array.value_unchecked(i) };
                *hash = value.hash_one(random_state);
            }
        }
    }
}

/// Hashes one array into the `hashes_buffer`
/// If `rehash==true` this combines the previous hash value in the buffer
/// with the new hash using `combine_hashes`
#[cfg(not(feature = "force_hash_collisions"))]
fn hash_array<T>(
    array: &T,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
    rehash: bool,
) where
    T: ArrayAccessor,
    T::Item: HashValue,
{
    assert_eq!(
        hashes_buffer.len(),
        array.len(),
        "hashes_buffer and array should be of equal length"
    );

    if array.null_count() == 0 {
        if rehash {
            for (i, hash) in hashes_buffer.iter_mut().enumerate() {
                let value = unsafe { array.value_unchecked(i) };
                *hash = combine_hashes(value.hash_one(random_state), *hash);
            }
        } else {
            for (i, hash) in hashes_buffer.iter_mut().enumerate() {
                let value = unsafe { array.value_unchecked(i) };
                *hash = value.hash_one(random_state);
            }
        }
    } else if rehash {
        for (i, hash) in hashes_buffer.iter_mut().enumerate() {
            if !array.is_null(i) {
                let value = unsafe { array.value_unchecked(i) };
                *hash = combine_hashes(value.hash_one(random_state), *hash);
            }
        }
    } else {
        for (i, hash) in hashes_buffer.iter_mut().enumerate() {
            if !array.is_null(i) {
                let value = unsafe { array.value_unchecked(i) };
                *hash = value.hash_one(random_state);
            }
        }
    }
}

/// Hash a StringView or BytesView array
///
/// Templated to optimize inner loop based on presence of nulls and external buffers.
///
/// HAS_NULLS: do we have to check null in the inner loop
/// HAS_BUFFERS: if true, array has external buffers; if false, all strings are inlined/ less then 12 bytes
/// REHASH: if true, combining with existing hash, otherwise initializing
#[inline(never)]
fn hash_string_view_array_inner<
    T: ByteViewType,
    const HAS_NULLS: bool,
    const HAS_BUFFERS: bool,
    const REHASH: bool,
>(
    array: &GenericByteViewArray<T>,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
) {
    assert_eq!(
        hashes_buffer.len(),
        array.len(),
        "hashes_buffer and array should be of equal length"
    );

    let buffers = array.data_buffers();
    let view_bytes = |view_len: u32, view: u128| {
        let view = ByteView::from(view);
        let offset = view.offset as usize;
        // SAFETY: view is a valid view as it came from the array
        unsafe {
            let data = buffers.get_unchecked(view.buffer_index as usize);
            data.get_unchecked(offset..offset + view_len as usize)
        }
    };

    let hashes_and_views = hashes_buffer.iter_mut().zip(array.views().iter());
    for (i, (hash, &v)) in hashes_and_views.enumerate() {
        if HAS_NULLS && array.is_null(i) {
            continue;
        }
        let view_len = v as u32;
        // all views are inlined, no need to access external buffers
        if !HAS_BUFFERS || view_len <= 12 {
            if REHASH {
                *hash = combine_hashes(v.hash_one(random_state), *hash);
            } else {
                *hash = v.hash_one(random_state);
            }
            continue;
        }
        // view is not inlined, so we need to hash the bytes as well
        let value = view_bytes(view_len, v);
        if REHASH {
            *hash = combine_hashes(value.hash_one(random_state), *hash);
        } else {
            *hash = value.hash_one(random_state);
        }
    }
}

/// Builds hash values for array views and writes them into `hashes_buffer`
/// If `rehash==true` this combines the previous hash value in the buffer
/// with the new hash using `combine_hashes`
#[cfg(not(feature = "force_hash_collisions"))]
fn hash_generic_byte_view_array<T: ByteViewType>(
    array: &GenericByteViewArray<T>,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
    rehash: bool,
) {
    // instantiate the correct version based on presence of nulls and external buffers
    match (
        array.null_count() != 0,
        !array.data_buffers().is_empty(),
        rehash,
    ) {
        // no nulls or buffers ==> hash the inlined views directly
        // don't call the inner function as Rust seems better able to inline this simpler code (2-3% faster)
        (false, false, false) => {
            for (hash, &view) in hashes_buffer.iter_mut().zip(array.views().iter()) {
                *hash = view.hash_one(random_state);
            }
        }
        (false, false, true) => {
            for (hash, &view) in hashes_buffer.iter_mut().zip(array.views().iter()) {
                *hash = combine_hashes(view.hash_one(random_state), *hash);
            }
        }
        (false, true, false) => hash_string_view_array_inner::<T, false, true, false>(
            array,
            random_state,
            hashes_buffer,
        ),
        (false, true, true) => hash_string_view_array_inner::<T, false, true, true>(
            array,
            random_state,
            hashes_buffer,
        ),
        (true, false, false) => hash_string_view_array_inner::<T, true, false, false>(
            array,
            random_state,
            hashes_buffer,
        ),
        (true, false, true) => hash_string_view_array_inner::<T, true, false, true>(
            array,
            random_state,
            hashes_buffer,
        ),
        (true, true, false) => hash_string_view_array_inner::<T, true, true, false>(
            array,
            random_state,
            hashes_buffer,
        ),
        (true, true, true) => hash_string_view_array_inner::<T, true, true, true>(
            array,
            random_state,
            hashes_buffer,
        ),
    }
}

/// Helper function to update hash for a dictionary key if the value is valid
#[cfg(not(feature = "force_hash_collisions"))]
#[inline]
fn update_hash_for_dict_key(
    hash: &mut u64,
    dict_hashes: &[u64],
    dict_values: &dyn Array,
    idx: usize,
    multi_col: bool,
) {
    if dict_values.is_valid(idx) {
        if multi_col {
            *hash = combine_hashes(dict_hashes[idx], *hash);
        } else {
            *hash = dict_hashes[idx];
        }
    }
    // no update for invalid dictionary value
}

/// Hash the values in a dictionary array
#[cfg(not(feature = "force_hash_collisions"))]
fn hash_dictionary<K: ArrowDictionaryKeyType>(
    array: &DictionaryArray<K>,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
    multi_col: bool,
) -> Result<()> {
    // Hash each dictionary value once, and then use that computed
    // hash for each key value to avoid a potentially expensive
    // redundant hashing for large dictionary elements (e.g. strings)
    let dict_values = array.values();
    let mut dict_hashes = vec![0; dict_values.len()];
    create_hashes([dict_values], random_state, &mut dict_hashes)?;

    // combine hash for each index in values
    for (hash, key) in hashes_buffer.iter_mut().zip(array.keys().iter()) {
        if let Some(key) = key {
            let idx = key.as_usize();
            update_hash_for_dict_key(
                hash,
                &dict_hashes,
                dict_values.as_ref(),
                idx,
                multi_col,
            );
        } // no update for Null key
    }
    Ok(())
}

#[cfg(not(feature = "force_hash_collisions"))]
fn hash_struct_array(
    array: &StructArray,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
) -> Result<()> {
    let nulls = array.nulls();
    let row_len = array.len();

    let valid_row_indices: Vec<usize> = if let Some(nulls) = nulls {
        nulls.valid_indices().collect()
    } else {
        (0..row_len).collect()
    };

    // Create hashes for each row that combines the hashes over all the column at that row.
    let mut values_hashes = vec![0u64; row_len];
    create_hashes(array.columns(), random_state, &mut values_hashes)?;

    for i in valid_row_indices {
        let hash = &mut hashes_buffer[i];
        *hash = combine_hashes(*hash, values_hashes[i]);
    }

    Ok(())
}

// only adding this `cfg` b/c this function is only used with this `cfg`
#[cfg(not(feature = "force_hash_collisions"))]
fn hash_map_array(
    array: &MapArray,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
) -> Result<()> {
    let nulls = array.nulls();
    let offsets = array.offsets();

    // Create hashes for each entry in each row
    let mut values_hashes = vec![0u64; array.entries().len()];
    create_hashes(array.entries().columns(), random_state, &mut values_hashes)?;

    // Combine the hashes for entries on each row with each other and previous hash for that row
    if let Some(nulls) = nulls {
        for (i, (start, stop)) in offsets.iter().zip(offsets.iter().skip(1)).enumerate() {
            if nulls.is_valid(i) {
                let hash = &mut hashes_buffer[i];
                for values_hash in &values_hashes[start.as_usize()..stop.as_usize()] {
                    *hash = combine_hashes(*hash, *values_hash);
                }
            }
        }
    } else {
        for (i, (start, stop)) in offsets.iter().zip(offsets.iter().skip(1)).enumerate() {
            let hash = &mut hashes_buffer[i];
            for values_hash in &values_hashes[start.as_usize()..stop.as_usize()] {
                *hash = combine_hashes(*hash, *values_hash);
            }
        }
    }

    Ok(())
}

#[cfg(not(feature = "force_hash_collisions"))]
fn hash_list_array<OffsetSize>(
    array: &GenericListArray<OffsetSize>,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
) -> Result<()>
where
    OffsetSize: OffsetSizeTrait,
{
    let values = array.values();
    let offsets = array.value_offsets();
    let nulls = array.nulls();
    let mut values_hashes = vec![0u64; values.len()];
    create_hashes([values], random_state, &mut values_hashes)?;
    if let Some(nulls) = nulls {
        for (i, (start, stop)) in offsets.iter().zip(offsets.iter().skip(1)).enumerate() {
            if nulls.is_valid(i) {
                let hash = &mut hashes_buffer[i];
                for values_hash in &values_hashes[start.as_usize()..stop.as_usize()] {
                    *hash = combine_hashes(*hash, *values_hash);
                }
            }
        }
    } else {
        for (i, (start, stop)) in offsets.iter().zip(offsets.iter().skip(1)).enumerate() {
            let hash = &mut hashes_buffer[i];
            for values_hash in &values_hashes[start.as_usize()..stop.as_usize()] {
                *hash = combine_hashes(*hash, *values_hash);
            }
        }
    }
    Ok(())
}

#[cfg(not(feature = "force_hash_collisions"))]
fn hash_union_array(
    array: &UnionArray,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
) -> Result<()> {
    use std::collections::HashMap;

    let DataType::Union(union_fields, _mode) = array.data_type() else {
        unreachable!()
    };

    let mut child_hashes = HashMap::with_capacity(union_fields.len());

    for (type_id, _field) in union_fields.iter() {
        let child = array.child(type_id);
        let mut child_hash_buffer = vec![0; child.len()];
        create_hashes([child], random_state, &mut child_hash_buffer)?;

        child_hashes.insert(type_id, child_hash_buffer);
    }

    #[expect(clippy::needless_range_loop)]
    for i in 0..array.len() {
        let type_id = array.type_id(i);
        let child_offset = array.value_offset(i);

        let child_hash = child_hashes.get(&type_id).expect("invalid type_id");
        hashes_buffer[i] = combine_hashes(hashes_buffer[i], child_hash[child_offset]);
    }

    Ok(())
}

#[cfg(not(feature = "force_hash_collisions"))]
fn hash_fixed_list_array(
    array: &FixedSizeListArray,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
) -> Result<()> {
    let values = array.values();
    let value_length = array.value_length() as usize;
    let nulls = array.nulls();
    let mut values_hashes = vec![0u64; values.len()];
    create_hashes([values], random_state, &mut values_hashes)?;
    if let Some(nulls) = nulls {
        for i in 0..array.len() {
            if nulls.is_valid(i) {
                let hash = &mut hashes_buffer[i];
                for values_hash in
                    &values_hashes[i * value_length..(i + 1) * value_length]
                {
                    *hash = combine_hashes(*hash, *values_hash);
                }
            }
        }
    } else {
        for i in 0..array.len() {
            let hash = &mut hashes_buffer[i];
            for values_hash in &values_hashes[i * value_length..(i + 1) * value_length] {
                *hash = combine_hashes(*hash, *values_hash);
            }
        }
    }
    Ok(())
}

#[cfg(not(feature = "force_hash_collisions"))]
fn hash_run_array<R: RunEndIndexType>(
    array: &RunArray<R>,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
    rehash: bool,
) -> Result<()> {
    // We find the relevant runs that cover potentially sliced arrays, so we can only hash those
    // values. Then we find the runs that refer to the original runs and ensure that we apply
    // hashes correctly to the sliced, whether sliced at the start, end, or both.
    let array_offset = array.offset();
    let array_len = array.len();

    if array_len == 0 {
        return Ok(());
    }

    let run_ends = array.run_ends();
    let run_ends_values = run_ends.values();
    let values = array.values();

    let start_physical_index = array.get_start_physical_index();
    // get_end_physical_index returns the inclusive last index, but we need the exclusive range end
    // for the operations we use below.
    let end_physical_index = array.get_end_physical_index() + 1;

    let sliced_values = values.slice(
        start_physical_index,
        end_physical_index - start_physical_index,
    );
    let mut values_hashes = vec![0u64; sliced_values.len()];
    create_hashes(
        std::slice::from_ref(&sliced_values),
        random_state,
        &mut values_hashes,
    )?;

    let mut start_in_slice = 0;
    for (adjusted_physical_index, &absolute_run_end) in run_ends_values
        [start_physical_index..end_physical_index]
        .iter()
        .enumerate()
    {
        let is_null_value = sliced_values.is_null(adjusted_physical_index);
        let absolute_run_end = absolute_run_end.as_usize();

        let end_in_slice = (absolute_run_end - array_offset).min(array_len);

        if rehash {
            if !is_null_value {
                let value_hash = values_hashes[adjusted_physical_index];
                for hash in hashes_buffer
                    .iter_mut()
                    .take(end_in_slice)
                    .skip(start_in_slice)
                {
                    *hash = combine_hashes(value_hash, *hash);
                }
            }
        } else {
            let value_hash = values_hashes[adjusted_physical_index];
            hashes_buffer[start_in_slice..end_in_slice].fill(value_hash);
        }

        start_in_slice = end_in_slice;
    }

    Ok(())
}

/// Internal helper function that hashes a single array and either initializes or combines
/// the hash values in the buffer.
#[cfg(not(feature = "force_hash_collisions"))]
fn hash_single_array(
    array: &dyn Array,
    random_state: &RandomState,
    hashes_buffer: &mut [u64],
    rehash: bool,
) -> Result<()> {
    downcast_primitive_array! {
        array => hash_array_primitive(array, random_state, hashes_buffer, rehash),
        DataType::Null => hash_null(random_state, hashes_buffer, rehash),
        DataType::Boolean => hash_array(&as_boolean_array(array)?, random_state, hashes_buffer, rehash),
        DataType::Utf8 => hash_array(&as_string_array(array)?, random_state, hashes_buffer, rehash),
        DataType::Utf8View => hash_generic_byte_view_array(as_string_view_array(array)?, random_state, hashes_buffer, rehash),
        DataType::LargeUtf8 => hash_array(&as_largestring_array(array), random_state, hashes_buffer, rehash),
        DataType::Binary => hash_array(&as_generic_binary_array::<i32>(array)?, random_state, hashes_buffer, rehash),
        DataType::BinaryView => hash_generic_byte_view_array(as_binary_view_array(array)?, random_state, hashes_buffer, rehash),
        DataType::LargeBinary => hash_array(&as_generic_binary_array::<i64>(array)?, random_state, hashes_buffer, rehash),
        DataType::FixedSizeBinary(_) => {
            let array: &FixedSizeBinaryArray = array.as_any().downcast_ref().unwrap();
            hash_array(&array, random_state, hashes_buffer, rehash)
        }
        DataType::Dictionary(_, _) => downcast_dictionary_array! {
            array => hash_dictionary(array, random_state, hashes_buffer, rehash)?,
            _ => unreachable!()
        }
        DataType::Struct(_) => {
            let array = as_struct_array(array)?;
            hash_struct_array(array, random_state, hashes_buffer)?;
        }
        DataType::List(_) => {
            let array = as_list_array(array)?;
            hash_list_array(array, random_state, hashes_buffer)?;
        }
        DataType::LargeList(_) => {
            let array = as_large_list_array(array)?;
            hash_list_array(array, random_state, hashes_buffer)?;
        }
        DataType::Map(_, _) => {
            let array = as_map_array(array)?;
            hash_map_array(array, random_state, hashes_buffer)?;
        }
        DataType::FixedSizeList(_,_) => {
            let array = as_fixed_size_list_array(array)?;
            hash_fixed_list_array(array, random_state, hashes_buffer)?;
        }
        DataType::Union(_, _) => {
            let array = as_union_array(array)?;
            hash_union_array(array, random_state, hashes_buffer)?;
        }
        DataType::RunEndEncoded(_, _) => downcast_run_array! {
            array => hash_run_array(array, random_state, hashes_buffer, rehash)?,
            _ => unreachable!()
        }
        _ => {
            // This is internal because we should have caught this before.
            return _internal_err!(
                "Unsupported data type in hasher: {}",
                array.data_type()
            );
        }
    }
    Ok(())
}

/// Test version of `hash_single_array` that forces all hashes to collide to zero.
#[cfg(feature = "force_hash_collisions")]
fn hash_single_array(
    _array: &dyn Array,
    _random_state: &RandomState,
    hashes_buffer: &mut [u64],
    _rehash: bool,
) -> Result<()> {
    for hash in hashes_buffer.iter_mut() {
        *hash = 0
    }
    Ok(())
}

/// Something that can be returned as a `&dyn Array`.
///
/// We want `create_hashes` to accept either `&dyn Array` or `ArrayRef`,
/// and this seems the best way to do so.
///
/// We tried having it accept `AsRef<dyn Array>`
/// but that is not implemented for and cannot be implemented for
/// `&dyn Array` so callers that have the latter would not be able
/// to call `create_hashes` directly. This shim trait makes it possible.
pub trait AsDynArray {
    fn as_dyn_array(&self) -> &dyn Array;
}

impl AsDynArray for dyn Array {
    fn as_dyn_array(&self) -> &dyn Array {
        self
    }
}

impl AsDynArray for &dyn Array {
    fn as_dyn_array(&self) -> &dyn Array {
        *self
    }
}

impl AsDynArray for ArrayRef {
    fn as_dyn_array(&self) -> &dyn Array {
        self.as_ref()
    }
}

impl AsDynArray for &ArrayRef {
    fn as_dyn_array(&self) -> &dyn Array {
        self.as_ref()
    }
}

/// Creates hash values for every row, based on the values in the columns.
///
/// The number of rows to hash is determined by `hashes_buffer.len()`.
/// `hashes_buffer` should be pre-sized appropriately.
pub fn create_hashes<'a, I, T>(
    arrays: I,
    random_state: &RandomState,
    hashes_buffer: &'a mut [u64],
) -> Result<&'a mut [u64]>
where
    I: IntoIterator<Item = T>,
    T: AsDynArray,
{
    for (i, array) in arrays.into_iter().enumerate() {
        // combine hashes with `combine_hashes` for all columns besides the first
        let rehash = i >= 1;
        hash_single_array(array.as_dyn_array(), random_state, hashes_buffer, rehash)?;
    }
    Ok(hashes_buffer)
}

#[cfg(test)]
mod tests {
    use std::sync::Arc;

    use arrow::array::*;
    #[cfg(not(feature = "force_hash_collisions"))]
    use arrow::datatypes::*;

    use super::*;

    #[test]
    fn create_hashes_for_decimal_array() -> Result<()> {
        let array = vec![1, 2, 3, 4]
            .into_iter()
            .map(Some)
            .collect::<Decimal128Array>()
            .with_precision_and_scale(20, 3)
            .unwrap();
        let array_ref: ArrayRef = Arc::new(array);
        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let hashes_buff = &mut vec![0; array_ref.len()];
        let hashes = create_hashes(&[array_ref], &random_state, hashes_buff)?;
        assert_eq!(hashes.len(), 4);
        Ok(())
    }

    #[test]
    fn create_hashes_for_empty_fixed_size_lit() -> Result<()> {
        let empty_array = FixedSizeListBuilder::new(StringBuilder::new(), 1).finish();
        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let hashes_buff = &mut [0; 0];
        let hashes = create_hashes(
            &[Arc::new(empty_array) as ArrayRef],
            &random_state,
            hashes_buff,
        )?;
        assert_eq!(hashes, &Vec::<u64>::new());
        Ok(())
    }

    #[test]
    fn create_hashes_for_float_arrays() -> Result<()> {
        let f32_arr: ArrayRef =
            Arc::new(Float32Array::from(vec![0.12, 0.5, 1f32, 444.7]));
        let f64_arr: ArrayRef =
            Arc::new(Float64Array::from(vec![0.12, 0.5, 1f64, 444.7]));

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let hashes_buff = &mut vec![0; f32_arr.len()];
        let hashes = create_hashes(&[f32_arr], &random_state, hashes_buff)?;
        assert_eq!(hashes.len(), 4,);

        let hashes = create_hashes(&[f64_arr], &random_state, hashes_buff)?;
        assert_eq!(hashes.len(), 4,);

        Ok(())
    }

    macro_rules! create_hash_binary {
        ($NAME:ident, $ARRAY:ty) => {
            #[cfg(not(feature = "force_hash_collisions"))]
            #[test]
            fn $NAME() {
                let binary = [
                    Some(b"short".to_byte_slice()),
                    None,
                    Some(b"long but different 12 bytes string"),
                    Some(b"short2"),
                    Some(b"Longer than 12 bytes string"),
                    Some(b"short"),
                    Some(b"Longer than 12 bytes string"),
                ];

                let binary_array: ArrayRef =
                    Arc::new(binary.iter().cloned().collect::<$ARRAY>());

                let random_state = RandomState::with_seeds(0, 0, 0, 0);

                let mut binary_hashes = vec![0; binary.len()];
                create_hashes(&[binary_array], &random_state, &mut binary_hashes)
                    .unwrap();

                // Null values result in a zero hash,
                for (val, hash) in binary.iter().zip(binary_hashes.iter()) {
                    match val {
                        Some(_) => assert_ne!(*hash, 0),
                        None => assert_eq!(*hash, 0),
                    }
                }

                // Same values should map to same hash values
                assert_eq!(binary[0], binary[5]);
                assert_eq!(binary[4], binary[6]);

                // different binary should map to different hash values
                assert_ne!(binary[0], binary[2]);
            }
        };
    }

    create_hash_binary!(binary_array, BinaryArray);
    create_hash_binary!(large_binary_array, LargeBinaryArray);
    create_hash_binary!(binary_view_array, BinaryViewArray);

    #[test]
    fn create_hashes_fixed_size_binary() -> Result<()> {
        let input_arg = vec![vec![1, 2], vec![5, 6], vec![5, 6]];
        let fixed_size_binary_array: ArrayRef =
            Arc::new(FixedSizeBinaryArray::try_from_iter(input_arg.into_iter()).unwrap());

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let hashes_buff = &mut vec![0; fixed_size_binary_array.len()];
        let hashes =
            create_hashes(&[fixed_size_binary_array], &random_state, hashes_buff)?;
        assert_eq!(hashes.len(), 3,);

        Ok(())
    }

    macro_rules! create_hash_string {
        ($NAME:ident, $ARRAY:ty) => {
            #[cfg(not(feature = "force_hash_collisions"))]
            #[test]
            fn $NAME() {
                let strings = [
                    Some("short"),
                    None,
                    Some("long but different 12 bytes string"),
                    Some("short2"),
                    Some("Longer than 12 bytes string"),
                    Some("short"),
                    Some("Longer than 12 bytes string"),
                ];

                let string_array: ArrayRef =
                    Arc::new(strings.iter().cloned().collect::<$ARRAY>());
                let dict_array: ArrayRef = Arc::new(
                    strings
                        .iter()
                        .cloned()
                        .collect::<DictionaryArray<Int8Type>>(),
                );

                let random_state = RandomState::with_seeds(0, 0, 0, 0);

                let mut string_hashes = vec![0; strings.len()];
                create_hashes(&[string_array], &random_state, &mut string_hashes)
                    .unwrap();

                let mut dict_hashes = vec![0; strings.len()];
                create_hashes(&[dict_array], &random_state, &mut dict_hashes).unwrap();

                // Null values result in a zero hash,
                for (val, hash) in strings.iter().zip(string_hashes.iter()) {
                    match val {
                        Some(_) => assert_ne!(*hash, 0),
                        None => assert_eq!(*hash, 0),
                    }
                }

                // same logical values should hash to the same hash value
                assert_eq!(string_hashes, dict_hashes);

                // Same values should map to same hash values
                assert_eq!(strings[0], strings[5]);
                assert_eq!(strings[4], strings[6]);

                // different strings should map to different hash values
                assert_ne!(strings[0], strings[2]);
            }
        };
    }

    create_hash_string!(string_array, StringArray);
    create_hash_string!(large_string_array, LargeStringArray);
    create_hash_string!(string_view_array, StringArray);
    create_hash_string!(dict_string_array, DictionaryArray<Int8Type>);

    #[test]
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_run_array() -> Result<()> {
        let values = Arc::new(Int32Array::from(vec![10, 20, 30]));
        let run_ends = Arc::new(Int32Array::from(vec![2, 5, 7]));
        let array = Arc::new(RunArray::try_new(&run_ends, values.as_ref()).unwrap());

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let hashes_buff = &mut vec![0; array.len()];
        let hashes = create_hashes(
            &[Arc::clone(&array) as ArrayRef],
            &random_state,
            hashes_buff,
        )?;

        assert_eq!(hashes.len(), 7);
        assert_eq!(hashes[0], hashes[1]);
        assert_eq!(hashes[2], hashes[3]);
        assert_eq!(hashes[3], hashes[4]);
        assert_eq!(hashes[5], hashes[6]);
        assert_ne!(hashes[0], hashes[2]);
        assert_ne!(hashes[2], hashes[5]);
        assert_ne!(hashes[0], hashes[5]);

        Ok(())
    }

    #[test]
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_multi_column_hash_with_run_array() -> Result<()> {
        let int_array = Arc::new(Int32Array::from(vec![1, 2, 3, 4, 5, 6, 7]));
        let values = Arc::new(StringArray::from(vec!["foo", "bar", "baz"]));
        let run_ends = Arc::new(Int32Array::from(vec![2, 5, 7]));
        let run_array = Arc::new(RunArray::try_new(&run_ends, values.as_ref()).unwrap());

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut one_col_hashes = vec![0; int_array.len()];
        create_hashes(
            &[Arc::clone(&int_array) as ArrayRef],
            &random_state,
            &mut one_col_hashes,
        )?;

        let mut two_col_hashes = vec![0; int_array.len()];
        create_hashes(
            &[
                Arc::clone(&int_array) as ArrayRef,
                Arc::clone(&run_array) as ArrayRef,
            ],
            &random_state,
            &mut two_col_hashes,
        )?;

        assert_eq!(one_col_hashes.len(), 7);
        assert_eq!(two_col_hashes.len(), 7);
        assert_ne!(one_col_hashes, two_col_hashes);

        let diff_0_vs_1_one_col = one_col_hashes[0] != one_col_hashes[1];
        let diff_0_vs_1_two_col = two_col_hashes[0] != two_col_hashes[1];
        assert_eq!(diff_0_vs_1_one_col, diff_0_vs_1_two_col);

        let diff_2_vs_3_one_col = one_col_hashes[2] != one_col_hashes[3];
        let diff_2_vs_3_two_col = two_col_hashes[2] != two_col_hashes[3];
        assert_eq!(diff_2_vs_3_one_col, diff_2_vs_3_two_col);

        Ok(())
    }

    #[test]
    // Tests actual values of hashes, which are different if forcing collisions
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_dict_arrays() {
        let strings = [Some("foo"), None, Some("bar"), Some("foo"), None];

        let string_array: ArrayRef =
            Arc::new(strings.iter().cloned().collect::<StringArray>());
        let dict_array: ArrayRef = Arc::new(
            strings
                .iter()
                .cloned()
                .collect::<DictionaryArray<Int8Type>>(),
        );

        let random_state = RandomState::with_seeds(0, 0, 0, 0);

        let mut string_hashes = vec![0; strings.len()];
        create_hashes(&[string_array], &random_state, &mut string_hashes).unwrap();

        let mut dict_hashes = vec![0; strings.len()];
        create_hashes(&[dict_array], &random_state, &mut dict_hashes).unwrap();

        // Null values result in a zero hash,
        for (val, hash) in strings.iter().zip(string_hashes.iter()) {
            match val {
                Some(_) => assert_ne!(*hash, 0),
                None => assert_eq!(*hash, 0),
            }
        }

        // same logical values should hash to the same hash value
        assert_eq!(string_hashes, dict_hashes);

        // Same values should map to same hash values
        assert_eq!(strings[1], strings[4]);
        assert_eq!(dict_hashes[1], dict_hashes[4]);
        assert_eq!(strings[0], strings[3]);
        assert_eq!(dict_hashes[0], dict_hashes[3]);

        // different strings should map to different hash values
        assert_ne!(strings[0], strings[2]);
        assert_ne!(dict_hashes[0], dict_hashes[2]);
    }

    #[test]
    // Tests actual values of hashes, which are different if forcing collisions
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_list_arrays() {
        let data = vec![
            Some(vec![Some(0), Some(1), Some(2)]),
            None,
            Some(vec![Some(3), None, Some(5)]),
            Some(vec![Some(3), None, Some(5)]),
            None,
            Some(vec![Some(0), Some(1), Some(2)]),
            Some(vec![]),
        ];
        let list_array =
            Arc::new(ListArray::from_iter_primitive::<Int32Type, _, _>(data)) as ArrayRef;
        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut hashes = vec![0; list_array.len()];
        create_hashes(&[list_array], &random_state, &mut hashes).unwrap();
        assert_eq!(hashes[0], hashes[5]);
        assert_eq!(hashes[1], hashes[4]);
        assert_eq!(hashes[2], hashes[3]);
        assert_eq!(hashes[1], hashes[6]); // null vs empty list
    }

    #[test]
    // Tests actual values of hashes, which are different if forcing collisions
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_fixed_size_list_arrays() {
        let data = vec![
            Some(vec![Some(0), Some(1), Some(2)]),
            None,
            Some(vec![Some(3), None, Some(5)]),
            Some(vec![Some(3), None, Some(5)]),
            None,
            Some(vec![Some(0), Some(1), Some(2)]),
        ];
        let list_array =
            Arc::new(FixedSizeListArray::from_iter_primitive::<Int32Type, _, _>(
                data, 3,
            )) as ArrayRef;
        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut hashes = vec![0; list_array.len()];
        create_hashes(&[list_array], &random_state, &mut hashes).unwrap();
        assert_eq!(hashes[0], hashes[5]);
        assert_eq!(hashes[1], hashes[4]);
        assert_eq!(hashes[2], hashes[3]);
    }

    #[test]
    // Tests actual values of hashes, which are different if forcing collisions
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_struct_arrays() {
        use arrow::buffer::Buffer;

        let boolarr = Arc::new(BooleanArray::from(vec![
            false, false, true, true, true, true,
        ]));
        let i32arr = Arc::new(Int32Array::from(vec![10, 10, 20, 20, 30, 31]));

        let struct_array = StructArray::from((
            vec![
                (
                    Arc::new(Field::new("bool", DataType::Boolean, false)),
                    Arc::clone(&boolarr) as ArrayRef,
                ),
                (
                    Arc::new(Field::new("i32", DataType::Int32, false)),
                    Arc::clone(&i32arr) as ArrayRef,
                ),
                (
                    Arc::new(Field::new("i32", DataType::Int32, false)),
                    Arc::clone(&i32arr) as ArrayRef,
                ),
                (
                    Arc::new(Field::new("bool", DataType::Boolean, false)),
                    Arc::clone(&boolarr) as ArrayRef,
                ),
            ],
            Buffer::from(&[0b001011]),
        ));

        assert!(struct_array.is_valid(0));
        assert!(struct_array.is_valid(1));
        assert!(struct_array.is_null(2));
        assert!(struct_array.is_valid(3));
        assert!(struct_array.is_null(4));
        assert!(struct_array.is_null(5));

        let array = Arc::new(struct_array) as ArrayRef;

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut hashes = vec![0; array.len()];
        create_hashes(&[array], &random_state, &mut hashes).unwrap();
        assert_eq!(hashes[0], hashes[1]);
        // same value but the third row ( hashes[2] ) is null
        assert_ne!(hashes[2], hashes[3]);
        // different values but both are null
        assert_eq!(hashes[4], hashes[5]);
    }

    #[test]
    // Tests actual values of hashes, which are different if forcing collisions
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_struct_arrays_more_column_than_row() {
        let struct_array = StructArray::from(vec![
            (
                Arc::new(Field::new("bool", DataType::Boolean, false)),
                Arc::new(BooleanArray::from(vec![false, false])) as ArrayRef,
            ),
            (
                Arc::new(Field::new("i32-1", DataType::Int32, false)),
                Arc::new(Int32Array::from(vec![10, 10])) as ArrayRef,
            ),
            (
                Arc::new(Field::new("i32-2", DataType::Int32, false)),
                Arc::new(Int32Array::from(vec![10, 10])) as ArrayRef,
            ),
            (
                Arc::new(Field::new("i32-3", DataType::Int32, false)),
                Arc::new(Int32Array::from(vec![10, 10])) as ArrayRef,
            ),
        ]);

        assert!(struct_array.is_valid(0));
        assert!(struct_array.is_valid(1));

        let array = Arc::new(struct_array) as ArrayRef;
        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut hashes = vec![0; array.len()];
        create_hashes(&[array], &random_state, &mut hashes).unwrap();
        assert_eq!(hashes[0], hashes[1]);
    }

    #[test]
    // Tests actual values of hashes, which are different if forcing collisions
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_map_arrays() {
        let mut builder =
            MapBuilder::new(None, StringBuilder::new(), Int32Builder::new());
        // Row 0
        builder.keys().append_value("key1");
        builder.keys().append_value("key2");
        builder.values().append_value(1);
        builder.values().append_value(2);
        builder.append(true).unwrap();
        // Row 1
        builder.keys().append_value("key1");
        builder.keys().append_value("key2");
        builder.values().append_value(1);
        builder.values().append_value(2);
        builder.append(true).unwrap();
        // Row 2
        builder.keys().append_value("key1");
        builder.keys().append_value("key2");
        builder.values().append_value(1);
        builder.values().append_value(3);
        builder.append(true).unwrap();
        // Row 3
        builder.keys().append_value("key1");
        builder.keys().append_value("key3");
        builder.values().append_value(1);
        builder.values().append_value(2);
        builder.append(true).unwrap();
        // Row 4
        builder.keys().append_value("key1");
        builder.values().append_value(1);
        builder.append(true).unwrap();
        // Row 5
        builder.keys().append_value("key1");
        builder.values().append_null();
        builder.append(true).unwrap();
        // Row 6
        builder.append(true).unwrap();
        // Row 7
        builder.keys().append_value("key1");
        builder.values().append_value(1);
        builder.append(false).unwrap();

        let array = Arc::new(builder.finish()) as ArrayRef;

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut hashes = vec![0; array.len()];
        create_hashes(&[array], &random_state, &mut hashes).unwrap();
        assert_eq!(hashes[0], hashes[1]); // same value
        assert_ne!(hashes[0], hashes[2]); // different value
        assert_ne!(hashes[0], hashes[3]); // different key
        assert_ne!(hashes[0], hashes[4]); // missing an entry
        assert_ne!(hashes[4], hashes[5]); // filled vs null value
        assert_eq!(hashes[6], hashes[7]); // empty vs null map
    }

    #[test]
    // Tests actual values of hashes, which are different if forcing collisions
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_multi_column_hash_for_dict_arrays() {
        let strings1 = [Some("foo"), None, Some("bar")];
        let strings2 = [Some("blarg"), Some("blah"), None];

        let string_array: ArrayRef =
            Arc::new(strings1.iter().cloned().collect::<StringArray>());
        let dict_array: ArrayRef = Arc::new(
            strings2
                .iter()
                .cloned()
                .collect::<DictionaryArray<Int32Type>>(),
        );

        let random_state = RandomState::with_seeds(0, 0, 0, 0);

        let mut one_col_hashes = vec![0; strings1.len()];
        create_hashes(
            &[Arc::clone(&dict_array) as ArrayRef],
            &random_state,
            &mut one_col_hashes,
        )
        .unwrap();

        let mut two_col_hashes = vec![0; strings1.len()];
        create_hashes(
            &[dict_array, string_array],
            &random_state,
            &mut two_col_hashes,
        )
        .unwrap();

        assert_eq!(one_col_hashes.len(), 3);
        assert_eq!(two_col_hashes.len(), 3);

        assert_ne!(one_col_hashes, two_col_hashes);
    }

    #[test]
    fn test_create_hashes_from_arrays() {
        let int_array: ArrayRef = Arc::new(Int32Array::from(vec![1, 2, 3, 4]));
        let float_array: ArrayRef =
            Arc::new(Float64Array::from(vec![1.0, 2.0, 3.0, 4.0]));

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let hashes_buff = &mut vec![0; int_array.len()];
        let hashes =
            create_hashes(&[int_array, float_array], &random_state, hashes_buff).unwrap();
        assert_eq!(hashes.len(), 4,);
    }

    #[test]
    fn test_create_hashes_from_dyn_arrays() {
        let int_array: ArrayRef = Arc::new(Int32Array::from(vec![1, 2, 3, 4]));
        let float_array: ArrayRef =
            Arc::new(Float64Array::from(vec![1.0, 2.0, 3.0, 4.0]));

        // Verify that we can call create_hashes with only &dyn Array
        fn test(arr1: &dyn Array, arr2: &dyn Array) {
            let random_state = RandomState::with_seeds(0, 0, 0, 0);
            let hashes_buff = &mut vec![0; arr1.len()];
            let hashes = create_hashes([arr1, arr2], &random_state, hashes_buff).unwrap();
            assert_eq!(hashes.len(), 4,);
        }
        test(&*int_array, &*float_array);
    }

    #[test]
    fn test_create_hashes_equivalence() {
        let array: ArrayRef = Arc::new(Int32Array::from(vec![1, 2, 3, 4]));
        let random_state = RandomState::with_seeds(0, 0, 0, 0);

        let mut hashes1 = vec![0; array.len()];
        create_hashes(
            &[Arc::clone(&array) as ArrayRef],
            &random_state,
            &mut hashes1,
        )
        .unwrap();

        let mut hashes2 = vec![0; array.len()];
        create_hashes([array], &random_state, &mut hashes2).unwrap();

        assert_eq!(hashes1, hashes2);
    }

    #[test]
    fn test_with_hashes() {
        let array: ArrayRef = Arc::new(Int32Array::from(vec![1, 2, 3, 4]));
        let random_state = RandomState::with_seeds(0, 0, 0, 0);

        // Test that with_hashes produces the same results as create_hashes
        let mut expected_hashes = vec![0; array.len()];
        create_hashes([&array], &random_state, &mut expected_hashes).unwrap();

        let result = with_hashes([&array], &random_state, |hashes| {
            assert_eq!(hashes.len(), 4);
            // Verify hashes match expected values
            assert_eq!(hashes, &expected_hashes[..]);
            // Return a copy of the hashes
            Ok(hashes.to_vec())
        })
        .unwrap();

        // Verify callback result is returned correctly
        assert_eq!(result, expected_hashes);
    }

    #[test]
    fn test_with_hashes_multi_column() {
        let int_array: ArrayRef = Arc::new(Int32Array::from(vec![1, 2, 3]));
        let str_array: ArrayRef = Arc::new(StringArray::from(vec!["a", "b", "c"]));
        let random_state = RandomState::with_seeds(0, 0, 0, 0);

        // Test multi-column hashing
        let mut expected_hashes = vec![0; int_array.len()];
        create_hashes(
            [&int_array, &str_array],
            &random_state,
            &mut expected_hashes,
        )
        .unwrap();

        with_hashes([&int_array, &str_array], &random_state, |hashes| {
            assert_eq!(hashes.len(), 3);
            assert_eq!(hashes, &expected_hashes[..]);
            Ok(())
        })
        .unwrap();
    }

    #[test]
    fn test_with_hashes_empty_arrays() {
        let random_state = RandomState::with_seeds(0, 0, 0, 0);

        // Test that passing no arrays returns an error
        let empty: [&ArrayRef; 0] = [];
        let result = with_hashes(empty, &random_state, |_hashes| Ok(()));

        assert!(result.is_err());
        assert!(
            result
                .unwrap_err()
                .to_string()
                .contains("requires at least one array")
        );
    }

    #[test]
    fn test_with_hashes_reentrancy() {
        let array: ArrayRef = Arc::new(Int32Array::from(vec![1, 2, 3]));
        let array2: ArrayRef = Arc::new(Int32Array::from(vec![4, 5, 6]));
        let random_state = RandomState::with_seeds(0, 0, 0, 0);

        // Test that reentrant calls return an error instead of panicking
        let result = with_hashes([&array], &random_state, |_hashes| {
            // Try to call with_hashes again inside the callback
            with_hashes([&array2], &random_state, |_inner_hashes| Ok(()))
        });

        assert!(result.is_err());
        let err_msg = result.unwrap_err().to_string();
        assert!(
            err_msg.contains("reentrantly") || err_msg.contains("cannot be called"),
            "Error message should mention reentrancy: {err_msg}",
        );
    }

    #[test]
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_sparse_union_arrays() {
        // logical array: [int(5), str("foo"), int(10), int(5)]
        let int_array = Int32Array::from(vec![Some(5), None, Some(10), Some(5)]);
        let str_array = StringArray::from(vec![None, Some("foo"), None, None]);

        let type_ids = vec![0_i8, 1, 0, 0].into();
        let children = vec![
            Arc::new(int_array) as ArrayRef,
            Arc::new(str_array) as ArrayRef,
        ];

        let union_fields = [
            (0, Arc::new(Field::new("a", DataType::Int32, true))),
            (1, Arc::new(Field::new("b", DataType::Utf8, true))),
        ]
        .into_iter()
        .collect();

        let array = UnionArray::try_new(union_fields, type_ids, None, children).unwrap();
        let array_ref = Arc::new(array) as ArrayRef;

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut hashes = vec![0; array_ref.len()];
        create_hashes(&[array_ref], &random_state, &mut hashes).unwrap();

        // Rows 0 and 3 both have type_id=0 (int) with value 5
        assert_eq!(hashes[0], hashes[3]);
        // Row 0 (int 5) vs Row 2 (int 10) - different values
        assert_ne!(hashes[0], hashes[2]);
        // Row 0 (int) vs Row 1 (string) - different types
        assert_ne!(hashes[0], hashes[1]);
    }

    #[test]
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_sparse_union_arrays_with_nulls() {
        // logical array: [int(5), str("foo"), int(null), str(null)]
        let int_array = Int32Array::from(vec![Some(5), None, None, None]);
        let str_array = StringArray::from(vec![None, Some("foo"), None, None]);

        let type_ids = vec![0, 1, 0, 1].into();
        let children = vec![
            Arc::new(int_array) as ArrayRef,
            Arc::new(str_array) as ArrayRef,
        ];

        let union_fields = [
            (0, Arc::new(Field::new("a", DataType::Int32, true))),
            (1, Arc::new(Field::new("b", DataType::Utf8, true))),
        ]
        .into_iter()
        .collect();

        let array = UnionArray::try_new(union_fields, type_ids, None, children).unwrap();
        let array_ref = Arc::new(array) as ArrayRef;

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut hashes = vec![0; array_ref.len()];
        create_hashes(&[array_ref], &random_state, &mut hashes).unwrap();

        // row 2 (int null) and row 3 (str null) should have the same hash
        // because they are both null values
        assert_eq!(hashes[2], hashes[3]);

        // row 0 (int 5) vs row 2 (int null) - different (value vs null)
        assert_ne!(hashes[0], hashes[2]);

        // row 1 (str "foo") vs row 3 (str null) - different (value vs null)
        assert_ne!(hashes[1], hashes[3]);
    }

    #[test]
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_dense_union_arrays() {
        // creates a dense union array with int and string types
        // [67, "norm", 100, "macdonald", 67]
        let int_array = Int32Array::from(vec![67, 100, 67]);
        let str_array = StringArray::from(vec!["norm", "macdonald"]);

        let type_ids = vec![0, 1, 0, 1, 0].into();
        let offsets = vec![0, 0, 1, 1, 2].into();
        let children = vec![
            Arc::new(int_array) as ArrayRef,
            Arc::new(str_array) as ArrayRef,
        ];

        let union_fields = [
            (0, Arc::new(Field::new("a", DataType::Int32, false))),
            (1, Arc::new(Field::new("b", DataType::Utf8, false))),
        ]
        .into_iter()
        .collect();

        let array =
            UnionArray::try_new(union_fields, type_ids, Some(offsets), children).unwrap();
        let array_ref = Arc::new(array) as ArrayRef;

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut hashes = vec![0; array_ref.len()];
        create_hashes(&[array_ref], &random_state, &mut hashes).unwrap();

        // 67 vs "norm"
        assert_ne!(hashes[0], hashes[1]);
        // 67 vs 100
        assert_ne!(hashes[0], hashes[2]);
        // "norm" vs "macdonald"
        assert_ne!(hashes[1], hashes[3]);
        // 100 vs "macdonald"
        assert_ne!(hashes[2], hashes[3]);
        // 67 vs 67
        assert_eq!(hashes[0], hashes[4]);
    }

    #[test]
    #[cfg(not(feature = "force_hash_collisions"))]
    fn create_hashes_for_sliced_run_array() -> Result<()> {
        let values = Arc::new(Int32Array::from(vec![10, 20, 30]));
        let run_ends = Arc::new(Int32Array::from(vec![2, 5, 7]));
        let array = Arc::new(RunArray::try_new(&run_ends, values.as_ref()).unwrap());

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut full_hashes = vec![0; array.len()];
        create_hashes(
            &[Arc::clone(&array) as ArrayRef],
            &random_state,
            &mut full_hashes,
        )?;

        let array_ref: ArrayRef = Arc::clone(&array) as ArrayRef;
        let sliced_array = array_ref.slice(2, 3);

        let mut sliced_hashes = vec![0; sliced_array.len()];
        create_hashes(
            std::slice::from_ref(&sliced_array),
            &random_state,
            &mut sliced_hashes,
        )?;

        assert_eq!(sliced_hashes.len(), 3);
        assert_eq!(sliced_hashes[0], sliced_hashes[1]);
        assert_eq!(sliced_hashes[1], sliced_hashes[2]);
        assert_eq!(&sliced_hashes, &full_hashes[2..5]);

        Ok(())
    }

    #[test]
    #[cfg(not(feature = "force_hash_collisions"))]
    fn test_run_array_with_nulls() -> Result<()> {
        let values = Arc::new(Int32Array::from(vec![Some(10), None, Some(20)]));
        let run_ends = Arc::new(Int32Array::from(vec![2, 4, 6]));
        let array = Arc::new(RunArray::try_new(&run_ends, values.as_ref()).unwrap());

        let random_state = RandomState::with_seeds(0, 0, 0, 0);
        let mut hashes = vec![0; array.len()];
        create_hashes(
            &[Arc::clone(&array) as ArrayRef],
            &random_state,
            &mut hashes,
        )?;

        assert_eq!(hashes[0], hashes[1]);
        assert_ne!(hashes[0], 0);
        assert_eq!(hashes[2], hashes[3]);
        assert_eq!(hashes[2], 0);
        assert_eq!(hashes[4], hashes[5]);
        assert_ne!(hashes[4], 0);
        assert_ne!(hashes[0], hashes[4]);

        Ok(())
    }

    #[test]
    #[cfg(not(feature = "force_hash_collisions"))]
    fn test_run_array_with_nulls_multicolumn() -> Result<()> {
        let primitive_array = Arc::new(Int32Array::from(vec![Some(10), None, Some(20)]));
        let run_values = Arc::new(Int32Array::from(vec![Some(10), None, Some(20)]));
        let run_ends = Arc::new(Int32Array::from(vec![1, 2, 3]));
        let run_array =
            Arc::new(RunArray::try_new(&run_ends, run_values.as_ref()).unwrap());
        let second_col = Arc::new(Int32Array::from(vec![100, 200, 300]));

        let random_state = RandomState::with_seeds(0, 0, 0, 0);

        let mut primitive_hashes = vec![0; 3];
        create_hashes(
            &[
                Arc::clone(&primitive_array) as ArrayRef,
                Arc::clone(&second_col) as ArrayRef,
            ],
            &random_state,
            &mut primitive_hashes,
        )?;

        let mut run_hashes = vec![0; 3];
        create_hashes(
            &[
                Arc::clone(&run_array) as ArrayRef,
                Arc::clone(&second_col) as ArrayRef,
            ],
            &random_state,
            &mut run_hashes,
        )?;

        assert_eq!(primitive_hashes, run_hashes);

        Ok(())
    }
}