vortex_array/

patches.rs

use std::cmp::Ordering;
use std::fmt::Debug;
use std::hash::Hash;

use itertools::Itertools as _;
use num_traits::ToPrimitive;
use serde::{Deserialize, Serialize};
use vortex_buffer::BufferMut;
use vortex_dtype::Nullability::NonNullable;
use vortex_dtype::{DType, NativePType, PType, match_each_integer_ptype};
use vortex_error::{VortexError, VortexExpect, VortexResult, vortex_bail, vortex_err};
use vortex_mask::{AllOr, Mask};
use vortex_scalar::Scalar;

use crate::aliases::hash_map::HashMap;
use crate::arrays::PrimitiveArray;
use crate::compute::{
    SearchResult, SearchSortedSide, filter, scalar_at, search_sorted, search_sorted_usize,
    search_sorted_usize_many, slice, take, try_cast,
};
use crate::variants::PrimitiveArrayTrait;
use crate::{Array, ArrayRef, IntoArray, ToCanonical};

#[derive(
    Copy,
    Clone,
    Debug,
    Serialize,
    Deserialize,
    rkyv::Archive,
    rkyv::Serialize,
    rkyv::Deserialize,
    rkyv::bytecheck::CheckBytes,
)]
#[bytecheck(crate = rkyv::bytecheck)]
#[repr(C)]
pub struct PatchesMetadata {
    len: usize,
    offset: usize,
    indices_ptype: PType,
}

impl PatchesMetadata {
    pub fn new(len: usize, offset: usize, indices_ptype: PType) -> Self {
        Self {
            len,
            offset,
            indices_ptype,
        }
    }

    #[inline]
    pub fn len(&self) -> usize {
        self.len
    }

    #[inline]
    pub fn is_empty(&self) -> bool {
        self.len == 0
    }

    #[inline]
    pub fn offset(&self) -> usize {
        self.offset
    }

    #[inline]
    pub fn indices_dtype(&self) -> DType {
        assert!(
            self.indices_ptype.is_unsigned_int(),
            "Patch indices must be unsigned integers"
        );
        DType::Primitive(self.indices_ptype, NonNullable)
    }
}

/// A helper for working with patched arrays.
#[derive(Debug, Clone)]
pub struct Patches {
    array_len: usize,
    offset: usize,
    indices: ArrayRef,
    values: ArrayRef,
}

impl Patches {
    pub fn new(array_len: usize, offset: usize, indices: ArrayRef, values: ArrayRef) -> Self {
        assert_eq!(
            indices.len(),
            values.len(),
            "Patch indices and values must have the same length"
        );
        assert!(
            indices.dtype().is_unsigned_int(),
            "Patch indices must be unsigned integers"
        );
        assert!(
            indices.len() <= array_len,
            "Patch indices must be shorter than the array length"
        );
        assert!(!indices.is_empty(), "Patch indices must not be empty");
        let max = usize::try_from(
            &scalar_at(&indices, indices.len() - 1).vortex_expect("indices are not empty"),
        )
        .vortex_expect("indices must be a number");
        assert!(
            max - offset < array_len,
            "Patch indices {:?}, offset {} are longer than the array length {}",
            max,
            offset,
            array_len
        );
        Self::new_unchecked(array_len, offset, indices, values)
    }

    /// Construct new patches without validating any of the arguments
    ///
    /// # Safety
    ///
    /// Users have to assert that
    /// * Indices and values have the same length
    /// * Indices is an unsigned integer type
    /// * Indices must be sorted
    /// * Last value in indices is smaller than array_len
    pub fn new_unchecked(
        array_len: usize,
        offset: usize,
        indices: ArrayRef,
        values: ArrayRef,
    ) -> Self {
        Self {
            array_len,
            offset,
            indices,
            values,
        }
    }

    // TODO(ngates): remove this...
    pub fn into_parts(self) -> (usize, usize, ArrayRef, ArrayRef) {
        (self.array_len, self.offset, self.indices, self.values)
    }

    pub fn array_len(&self) -> usize {
        self.array_len
    }

    pub fn num_patches(&self) -> usize {
        self.indices.len()
    }

    pub fn dtype(&self) -> &DType {
        self.values.dtype()
    }

    pub fn indices(&self) -> &ArrayRef {
        &self.indices
    }

    pub fn into_indices(self) -> ArrayRef {
        self.indices
    }

    pub fn values(&self) -> &ArrayRef {
        &self.values
    }

    pub fn into_values(self) -> ArrayRef {
        self.values
    }

    pub fn offset(&self) -> usize {
        self.offset
    }

    pub fn indices_ptype(&self) -> PType {
        PType::try_from(self.indices.dtype()).vortex_expect("primitive indices")
    }

    pub fn to_metadata(&self, len: usize, dtype: &DType) -> VortexResult<PatchesMetadata> {
        if self.indices.len() > len {
            vortex_bail!(
                "Patch indices {} are longer than the array length {}",
                self.indices.len(),
                len
            );
        }
        if self.values.dtype() != dtype {
            vortex_bail!(
                "Patch values dtype {} does not match array dtype {}",
                self.values.dtype(),
                dtype
            );
        }
        Ok(PatchesMetadata {
            len: self.indices.len(),
            offset: self.offset,
            indices_ptype: PType::try_from(self.indices.dtype()).vortex_expect("primitive indices"),
        })
    }

    pub fn cast_values(self, values_dtype: &DType) -> VortexResult<Self> {
        Ok(Self::new_unchecked(
            self.array_len,
            self.offset,
            self.indices,
            try_cast(&self.values, values_dtype)?,
        ))
    }

    /// Get the patched value at a given index if it exists.
    pub fn get_patched(&self, index: usize) -> VortexResult<Option<Scalar>> {
        if let Some(patch_idx) = self.search_index(index)?.to_found() {
            scalar_at(self.values(), patch_idx).map(Some)
        } else {
            Ok(None)
        }
    }

    /// Return the insertion point of [index] in the [Self::indices].
    fn search_index(&self, index: usize) -> VortexResult<SearchResult> {
        search_sorted_usize(&self.indices, index + self.offset, SearchSortedSide::Left)
    }

    /// Return the search_sorted result for the given target re-mapped into the original indices.
    pub fn search_sorted<T: Into<Scalar>>(
        &self,
        target: T,
        side: SearchSortedSide,
    ) -> VortexResult<SearchResult> {
        search_sorted(self.values(), target.into(), side).and_then(|sr| {
            let sidx = sr.to_offsets_index(self.indices().len());
            let index = usize::try_from(&scalar_at(self.indices(), sidx)?)? - self.offset;
            Ok(match sr {
                // If we reached the end of patched values when searching then the result is one after the last patch index
                SearchResult::Found(i) => SearchResult::Found(if i == self.indices().len() {
                    index + 1
                } else {
                    index
                }),
                // If the result is NotFound we should return index that's one after the nearest not found index for the corresponding value
                SearchResult::NotFound(i) => {
                    SearchResult::NotFound(if i == 0 { index } else { index + 1 })
                }
            })
        })
    }

    /// Returns the minimum patch index
    pub fn min_index(&self) -> VortexResult<usize> {
        Ok(usize::try_from(&scalar_at(self.indices(), 0)?)? - self.offset)
    }

    /// Returns the maximum patch index
    pub fn max_index(&self) -> VortexResult<usize> {
        Ok(usize::try_from(&scalar_at(self.indices(), self.indices().len() - 1)?)? - self.offset)
    }

    /// Filter the patches by a mask, resulting in new patches for the filtered array.
    pub fn filter(&self, mask: &Mask) -> VortexResult<Option<Self>> {
        match mask.indices() {
            AllOr::All => Ok(Some(self.clone())),
            AllOr::None => Ok(None),
            AllOr::Some(mask_indices) => {
                let flat_indices = self.indices().to_primitive()?;
                match_each_integer_ptype!(flat_indices.ptype(), |$I| {
                    filter_patches_with_mask(
                        flat_indices.as_slice::<$I>(),
                        self.offset(),
                        self.values(),
                        mask_indices,
                    )
                })
            }
        }
    }

    /// Slice the patches by a range of the patched array.
    pub fn slice(&self, start: usize, stop: usize) -> VortexResult<Option<Self>> {
        let patch_start = self.search_index(start)?.to_index();
        let patch_stop = self.search_index(stop)?.to_index();

        if patch_start == patch_stop {
            return Ok(None);
        }

        // Slice out the values and indices
        let values = slice(self.values(), patch_start, patch_stop)?;
        let indices = slice(self.indices(), patch_start, patch_stop)?;

        Ok(Some(Self::new(
            stop - start,
            start + self.offset(),
            indices,
            values,
        )))
    }

    // https://docs.google.com/spreadsheets/d/1D9vBZ1QJ6mwcIvV5wIL0hjGgVchcEnAyhvitqWu2ugU
    const PREFER_MAP_WHEN_PATCHES_OVER_INDICES_LESS_THAN: f64 = 5.0;

    fn is_map_faster_than_search(&self, take_indices: &PrimitiveArray) -> bool {
        (self.num_patches() as f64 / take_indices.len() as f64)
            < Self::PREFER_MAP_WHEN_PATCHES_OVER_INDICES_LESS_THAN
    }

    /// Take the indices from the patches.
    pub fn take(&self, take_indices: &dyn Array) -> VortexResult<Option<Self>> {
        if take_indices.is_empty() {
            return Ok(None);
        }
        let take_indices = take_indices.to_primitive()?;
        if self.is_map_faster_than_search(&take_indices) {
            self.take_map(take_indices)
        } else {
            self.take_search(take_indices)
        }
    }

    pub fn take_search(&self, take_indices: PrimitiveArray) -> VortexResult<Option<Self>> {
        let new_length = take_indices.len();

        let Some((new_indices, values_indices)) = match_each_integer_ptype!(take_indices.ptype(), |$I| {
            take_search::<$I>(self.indices(), take_indices, self.offset())?
        }) else {
            return Ok(None);
        };

        Ok(Some(Self::new(
            new_length,
            0,
            new_indices,
            take(self.values(), &values_indices)?,
        )))
    }

    pub fn take_map(&self, take_indices: PrimitiveArray) -> VortexResult<Option<Self>> {
        let indices = self.indices.to_primitive()?;
        let new_length = take_indices.len();

        let Some((new_sparse_indices, value_indices)) = match_each_integer_ptype!(self.indices_ptype(), |$INDICES| {
            match_each_integer_ptype!(take_indices.ptype(), |$TAKE_INDICES| {
                take_map::<_, $TAKE_INDICES>(indices.as_slice::<$INDICES>(), take_indices, self.offset(), self.min_index()?, self.max_index()?)?
            })
        }) else {
            return Ok(None);
        };

        Ok(Some(Patches::new(
            new_length,
            0,
            new_sparse_indices,
            take(self.values(), &value_indices)?,
        )))
    }

    pub fn map_values<F>(self, f: F) -> VortexResult<Self>
    where
        F: FnOnce(ArrayRef) -> VortexResult<ArrayRef>,
    {
        let values = f(self.values)?;
        if self.indices.len() != values.len() {
            vortex_bail!(
                "map_values must preserve length: expected {} received {}",
                self.indices.len(),
                values.len()
            )
        }
        Ok(Self::new(self.array_len, self.offset, self.indices, values))
    }
}

fn take_search<T: NativePType + TryFrom<usize>>(
    indices: &dyn Array,
    take_indices: PrimitiveArray,
    indices_offset: usize,
) -> VortexResult<Option<(ArrayRef, ArrayRef)>>
where
    usize: TryFrom<T>,
    VortexError: From<<usize as TryFrom<T>>::Error>,
{
    let take_indices_validity = take_indices.validity();
    let take_indices = take_indices
        .as_slice::<T>()
        .iter()
        .copied()
        .map(usize::try_from)
        .map_ok(|idx| idx + indices_offset)
        .collect::<Result<Vec<_>, _>>()?;

    let (values_indices, new_indices): (BufferMut<u64>, BufferMut<u64>) =
        search_sorted_usize_many(indices, &take_indices, SearchSortedSide::Left)?
            .iter()
            .enumerate()
            .filter_map(|(idx_in_take, search_result)| {
                search_result
                    .to_found()
                    .map(|patch_idx| (patch_idx as u64, idx_in_take as u64))
            })
            .unzip();

    if new_indices.is_empty() {
        return Ok(None);
    }

    let new_indices = new_indices.into_array();
    let values_validity = take_indices_validity.take(&new_indices)?;
    Ok(Some((
        new_indices,
        PrimitiveArray::new(values_indices, values_validity).into_array(),
    )))
}

fn take_map<I: NativePType + Hash + Eq + TryFrom<usize>, T: NativePType>(
    indices: &[I],
    take_indices: PrimitiveArray,
    indices_offset: usize,
    min_index: usize,
    max_index: usize,
) -> VortexResult<Option<(ArrayRef, ArrayRef)>>
where
    usize: TryFrom<T>,
    VortexError: From<<I as TryFrom<usize>>::Error>,
{
    let take_indices_validity = take_indices.validity();
    let take_indices = take_indices.as_slice::<T>();
    let offset_i = I::try_from(indices_offset)?;

    let sparse_index_to_value_index: HashMap<I, usize> = indices
        .iter()
        .copied()
        .map(|idx| idx - offset_i)
        .enumerate()
        .map(|(value_index, sparse_index)| (sparse_index, value_index))
        .collect();
    let (new_sparse_indices, value_indices): (BufferMut<u64>, BufferMut<u64>) = take_indices
        .iter()
        .copied()
        .map(usize::try_from)
        .process_results(|iter| {
            iter.enumerate()
                .filter(|(_, ti)| *ti >= min_index && *ti <= max_index)
                .filter_map(|(new_sparse_index, take_sparse_index)| {
                    sparse_index_to_value_index
                        .get(
                            &I::try_from(take_sparse_index)
                                .vortex_expect("take_sparse_index is between min and max index"),
                        )
                        .map(|value_index| (new_sparse_index as u64, *value_index as u64))
                })
                .unzip()
        })
        .map_err(|_| vortex_err!("Failed to convert index to usize"))?;

    if new_sparse_indices.is_empty() {
        return Ok(None);
    }

    let new_sparse_indices = new_sparse_indices.into_array();
    let values_validity = take_indices_validity.take(&new_sparse_indices)?;
    Ok(Some((
        new_sparse_indices,
        PrimitiveArray::new(value_indices, values_validity).into_array(),
    )))
}

/// Filter patches with the provided mask (in flattened space).
///
/// The filter mask may contain indices that are non-patched. The return value of this function
/// is a new set of `Patches` with the indices relative to the provided `mask` rank, and the
/// patch values.
fn filter_patches_with_mask<T: ToPrimitive + Copy + Ord>(
    patch_indices: &[T],
    offset: usize,
    patch_values: &dyn Array,
    mask_indices: &[usize],
) -> VortexResult<Option<Patches>> {
    let true_count = mask_indices.len();
    let mut new_patch_indices = BufferMut::<u64>::with_capacity(true_count);
    let mut new_mask_indices = Vec::with_capacity(true_count);

    // Attempt to move the window by `STRIDE` elements on each iteration. This assumes that
    // the patches are relatively sparse compared to the overall mask, and so many indices in the
    // mask will end up being skipped.
    const STRIDE: usize = 4;

    let mut mask_idx = 0usize;
    let mut true_idx = 0usize;

    while mask_idx < patch_indices.len() && true_idx < true_count {
        // NOTE: we are searching for overlaps between sorted, unaligned indices in `patch_indices`
        //  and `mask_indices`. We assume that Patches are sparse relative to the global space of
        //  the mask (which covers both patch and non-patch values of the parent array), and so to
        //  quickly jump through regions with no overlap, we attempt to move our pointers by STRIDE
        //  elements on each iteration. If we cannot rule out overlap due to min/max values, we
        //  fallback to performing a two-way iterator merge.
        if (mask_idx + STRIDE) < patch_indices.len() && (true_idx + STRIDE) < mask_indices.len() {
            // Load a vector of each into our registers.
            let left_min = patch_indices[mask_idx].to_usize().vortex_expect("left_min") - offset;
            let left_max = patch_indices[mask_idx + STRIDE]
                .to_usize()
                .vortex_expect("left_max")
                - offset;
            let right_min = mask_indices[true_idx];
            let right_max = mask_indices[true_idx + STRIDE];

            if left_min > right_max {
                // Advance right side
                true_idx += STRIDE;
                continue;
            } else if right_min > left_max {
                mask_idx += STRIDE;
                continue;
            } else {
                // Fallthrough to direct comparison path.
            }
        }

        // Two-way sorted iterator merge:

        let left = patch_indices[mask_idx].to_usize().vortex_expect("left") - offset;
        let right = mask_indices[true_idx];

        match left.cmp(&right) {
            Ordering::Less => {
                mask_idx += 1;
            }
            Ordering::Greater => {
                true_idx += 1;
            }
            Ordering::Equal => {
                // Save the mask index as well as the positional index.
                new_mask_indices.push(mask_idx);
                new_patch_indices.push(true_idx as u64);

                mask_idx += 1;
                true_idx += 1;
            }
        }
    }

    if new_mask_indices.is_empty() {
        return Ok(None);
    }

    let new_patch_indices = new_patch_indices.into_array();
    let new_patch_values = filter(
        patch_values,
        &Mask::from_indices(patch_values.len(), new_mask_indices),
    )?;

    Ok(Some(Patches::new(
        true_count,
        0,
        new_patch_indices,
        new_patch_values,
    )))
}

#[cfg(test)]
mod test {
    use rstest::{fixture, rstest};
    use vortex_buffer::buffer;
    use vortex_mask::Mask;

    use crate::array::Array;
    use crate::arrays::PrimitiveArray;
    use crate::compute::{SearchResult, SearchSortedSide};
    use crate::patches::Patches;
    use crate::validity::Validity;
    use crate::{IntoArray, ToCanonical};

    #[test]
    fn test_filter() {
        let patches = Patches::new(
            100,
            0,
            buffer![10u32, 11, 20].into_array(),
            buffer![100, 110, 200].into_array(),
        );

        let filtered = patches
            .filter(&Mask::from_indices(100, vec![10, 20, 30]))
            .unwrap()
            .unwrap();

        let indices = filtered.indices().to_primitive().unwrap();
        let values = filtered.values().to_primitive().unwrap();
        assert_eq!(indices.as_slice::<u64>(), &[0, 1]);
        assert_eq!(values.as_slice::<i32>(), &[100, 200]);
    }

    #[fixture]
    fn patches() -> Patches {
        Patches::new(
            20,
            0,
            buffer![2u64, 9, 15].into_array(),
            PrimitiveArray::new(buffer![33_i32, 44, 55], Validity::AllValid).into_array(),
        )
    }

    #[rstest]
    fn search_larger_than(patches: Patches) {
        let res = patches.search_sorted(66, SearchSortedSide::Left).unwrap();
        assert_eq!(res, SearchResult::NotFound(16));
    }

    #[rstest]
    fn search_less_than(patches: Patches) {
        let res = patches.search_sorted(22, SearchSortedSide::Left).unwrap();
        assert_eq!(res, SearchResult::NotFound(2));
    }

    #[rstest]
    fn search_found(patches: Patches) {
        let res = patches.search_sorted(44, SearchSortedSide::Left).unwrap();
        assert_eq!(res, SearchResult::Found(9));
    }

    #[rstest]
    fn search_not_found_right(patches: Patches) {
        let res = patches.search_sorted(56, SearchSortedSide::Right).unwrap();
        assert_eq!(res, SearchResult::NotFound(16));
    }

    #[rstest]
    fn search_sliced(patches: Patches) {
        let sliced = patches.slice(7, 20).unwrap().unwrap();
        assert_eq!(
            sliced.search_sorted(22, SearchSortedSide::Left).unwrap(),
            SearchResult::NotFound(2)
        );
    }

    #[test]
    fn search_right() {
        let patches = Patches::new(
            2,
            0,
            buffer![0u64].into_array(),
            PrimitiveArray::new(buffer![0u8], Validity::AllValid).into_array(),
        );

        assert_eq!(
            patches.search_sorted(0, SearchSortedSide::Right).unwrap(),
            SearchResult::Found(1)
        );
        assert_eq!(
            patches.search_sorted(1, SearchSortedSide::Right).unwrap(),
            SearchResult::NotFound(1)
        );
    }

    #[rstest]
    fn take_wit_nulls(patches: Patches) {
        let taken = patches
            .take(
                &PrimitiveArray::new(buffer![9, 0], Validity::from_iter(vec![true, false]))
                    .into_array(),
            )
            .unwrap()
            .unwrap();
        let primitive_values = taken.values().to_primitive().unwrap();
        assert_eq!(taken.array_len(), 2);
        assert_eq!(primitive_values.as_slice::<i32>(), [44]);
        assert_eq!(
            primitive_values.validity_mask().unwrap(),
            Mask::from_iter(vec![true])
        );
    }
}