perf: Allow for arbitrary skips in Parquet Dictionary Decoding

crates/polars-arrow/src/bitmap/bitmask.rs

@@ -4,7 +4,7 @@ use std::simd::{LaneCount, Mask, MaskElement, SupportedLaneCount};
 use polars_utils::slice::load_padded_le_u64;
 
 use super::iterator::FastU56BitmapIter;
-use super::utils::{count_zeros, BitmapIter};
+use super::utils::{count_zeros, fmt, BitmapIter};
 use crate::bitmap::Bitmap;
 
 /// Returns the nth set bit in w, if n+1 bits are set. The indexing is
@@ -79,6 +79,15 @@ pub struct BitMask<'a> {
     len: usize,
 }
 
+impl std::fmt::Debug for BitMask<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self { bytes, offset, len } = self;
+        let offset_num_bytes = offset / 8;
+        let offset_in_byte = offset % 8;
+        fmt(&bytes[offset_num_bytes..], offset_in_byte, *len, f)
+    }
+}
+
 impl<'a> BitMask<'a> {
     pub fn from_bitmap(bitmap: &'a Bitmap) -> Self {
         let (bytes, offset, len) = bitmap.as_slice();
@@ -92,6 +101,13 @@ impl<'a> BitMask<'a> {
         self.len
     }
 
+    #[inline]
+    pub fn advance_by(&mut self, idx: usize) {
+        assert!(idx <= self.len);
+        self.offset += idx;
+        self.len -= idx;
+    }
+
     #[inline]
     pub fn split_at(&self, idx: usize) -> (Self, Self) {
         assert!(idx <= self.len);

crates/polars-parquet/src/arrow/read/deserialize/binview.rs

@@ -8,11 +8,11 @@ use arrow::bitmap::{Bitmap, MutableBitmap};
 use arrow::buffer::Buffer;
 use arrow::datatypes::{ArrowDataType, PhysicalType};
 
-use super::utils::dict_encoded::{append_validity, constrain_page_validity};
+use super::dictionary_encoded::{append_validity, constrain_page_validity};
 use super::utils::{
     dict_indices_decoder, filter_from_range, freeze_validity, unspecialized_decode,
 };
-use super::Filter;
+use super::{dictionary_encoded, Filter};
 use crate::parquet::encoding::{delta_byte_array, delta_length_byte_array, hybrid_rle, Encoding};
 use crate::parquet::error::{ParquetError, ParquetResult};
 use crate::parquet::page::{split_buffer, DataPage, DictPage};
@@ -521,7 +521,7 @@ impl utils::Decoder for BinViewDecoder {
 
                 let start_length = decoded.0.views().len();
 
-                utils::dict_encoded::decode_dict(
+                dictionary_encoded::decode_dict(
                     indexes.clone(),
                     dict,
                     state.is_optional,

crates/polars-parquet/src/arrow/read/deserialize/boolean.rs

@@ -5,7 +5,7 @@ use arrow::bitmap::{Bitmap, MutableBitmap};
 use arrow::datatypes::ArrowDataType;
 use polars_compute::filter::filter_boolean_kernel;
 
-use super::utils::dict_encoded::{append_validity, constrain_page_validity};
+use super::dictionary_encoded::{append_validity, constrain_page_validity};
 use super::utils::{
     self, decode_hybrid_rle_into_bitmap, filter_from_range, freeze_validity, Decoder, ExactSize,
 };

crates/polars-parquet/src/arrow/read/deserialize/dictionary_encoded/mod.rs

@@ -0,0 +1,233 @@
+use arrow::bitmap::bitmask::BitMask;
+use arrow::bitmap::{Bitmap, MutableBitmap};
+use arrow::types::{AlignedBytes, NativeType};
+use polars_compute::filter::filter_boolean_kernel;
+
+use super::ParquetError;
+use crate::parquet::encoding::hybrid_rle::HybridRleDecoder;
+use crate::parquet::error::ParquetResult;
+use crate::read::Filter;
+
+mod optional;
+mod optional_masked_dense;
+mod required;
+mod required_masked_dense;
+
+pub fn decode_dict<T: NativeType>(
+    values: HybridRleDecoder<'_>,
+    dict: &[T],
+    is_optional: bool,
+    page_validity: Option<&Bitmap>,
+    filter: Option<Filter>,
+    validity: &mut MutableBitmap,
+    target: &mut Vec<T>,
+) -> ParquetResult<()> {
+    decode_dict_dispatch(
+        values,
+        bytemuck::cast_slice(dict),
+        is_optional,
+        page_validity,
+        filter,
+        validity,
+        <T::AlignedBytes as AlignedBytes>::cast_vec_ref_mut(target),
+    )
+}
+
+#[inline(never)]
+pub fn decode_dict_dispatch<B: AlignedBytes>(
+    mut values: HybridRleDecoder<'_>,
+    dict: &[B],
+    is_optional: bool,
+    page_validity: Option<&Bitmap>,
+    filter: Option<Filter>,
+    validity: &mut MutableBitmap,
+    target: &mut Vec<B>,
+) -> ParquetResult<()> {
+    if cfg!(debug_assertions) && is_optional {
+        assert_eq!(target.len(), validity.len());
+    }
+
+    if is_optional {
+        append_validity(page_validity, filter.as_ref(), validity, values.len());
+    }
+
+    let page_validity = constrain_page_validity(values.len(), page_validity, filter.as_ref());
+
+    match (filter, page_validity) {
+        (None, None) => required::decode(values, dict, target, 0),
+        (Some(Filter::Range(rng)), None) => {
+            values.limit_to(rng.end);
+            required::decode(values, dict, target, rng.start)
+        },
+        (None, Some(page_validity)) => optional::decode(values, dict, page_validity, target, 0),
+        (Some(Filter::Range(rng)), Some(page_validity)) => {
+            optional::decode(values, dict, page_validity, target, rng.start)
+        },
+        (Some(Filter::Mask(filter)), None) => {
+            required_masked_dense::decode(values, dict, filter, target)
+        },
+        (Some(Filter::Mask(filter)), Some(page_validity)) => {
+            optional_masked_dense::decode(values, dict, filter, page_validity, target)
+        },
+    }?;
+
+    if cfg!(debug_assertions) && is_optional {
+        assert_eq!(target.len(), validity.len());
+    }
+
+    Ok(())
+}
+
+pub(crate) fn append_validity(
+    page_validity: Option<&Bitmap>,
+    filter: Option<&Filter>,
+    validity: &mut MutableBitmap,
+    values_len: usize,
+) {
+    match (page_validity, filter) {
+        (None, None) => validity.extend_constant(values_len, true),
+        (None, Some(f)) => validity.extend_constant(f.num_rows(), true),
+        (Some(page_validity), None) => validity.extend_from_bitmap(page_validity),
+        (Some(page_validity), Some(Filter::Range(rng))) => {
+            let page_validity = page_validity.clone();
+            validity.extend_from_bitmap(&page_validity.clone().sliced(rng.start, rng.len()))
+        },
+        (Some(page_validity), Some(Filter::Mask(mask))) => {
+            validity.extend_from_bitmap(&filter_boolean_kernel(page_validity, mask))
+        },
+    }
+}
+
+pub(crate) fn constrain_page_validity(
+    values_len: usize,
+    page_validity: Option<&Bitmap>,
+    filter: Option<&Filter>,
+) -> Option<Bitmap> {
+    let num_unfiltered_rows = match (filter.as_ref(), page_validity) {
+        (None, None) => values_len,
+        (None, Some(pv)) => {
+            debug_assert!(pv.len() >= values_len);
+            pv.len()
+        },
+        (Some(f), v) => {
+            if cfg!(debug_assertions) {
+                if let Some(v) = v {
+                    assert!(v.len() >= f.max_offset());
+                }
+            }
+
+            f.max_offset()
+        },
+    };
+
+    page_validity.map(|pv| {
+        if pv.len() > num_unfiltered_rows {
+            pv.clone().sliced(0, num_unfiltered_rows)
+        } else {
+            pv.clone()
+        }
+    })
+}
+
+#[cold]
+fn oob_dict_idx() -> ParquetError {
+    ParquetError::oos("Dictionary Index is out-of-bounds")
+}
+
+#[cold]
+fn no_more_bitpacked_values() -> ParquetError {
+    ParquetError::oos("Bitpacked Hybrid-RLE ran out before all values were served")
+}
+
+#[inline(always)]
+fn verify_dict_indices(indices: &[u32; 32], dict_size: usize) -> ParquetResult<()> {
+    let mut is_valid = true;
+    for &idx in indices {
+        is_valid &= (idx as usize) < dict_size;
+    }
+
+    if is_valid {
+        return Ok(());
+    }
+
+    Err(oob_dict_idx())
+}
+
+#[inline(always)]
+fn verify_dict_indices_slice(indices: &[u32], dict_size: usize) -> ParquetResult<()> {
+    let mut is_valid = true;
+    for &idx in indices {
+        is_valid &= (idx as usize) < dict_size;
+    }
+
+    if is_valid {
+        return Ok(());
+    }
+
+    Err(oob_dict_idx())
+}
+
+/// Skip over entire chunks in a [`HybridRleDecoder`] as long as all skipped chunks do not include
+/// more than `num_values_to_skip` values.
+#[inline(always)]
+fn required_skip_whole_chunks(
+    values: &mut HybridRleDecoder<'_>,
+    num_values_to_skip: &mut usize,
+) -> ParquetResult<()> {
+    if *num_values_to_skip == 0 {
+        return Ok(());
+    }
+
+    loop {
+        let mut values_clone = values.clone();
+        let Some(chunk_len) = values_clone.next_chunk_length()? else {
+            break;
+        };
+        if *num_values_to_skip < chunk_len {
+            break;
+        }
+        *values = values_clone;
+        *num_values_to_skip -= chunk_len;
+    }
+
+    Ok(())
+}
+
+/// Skip over entire chunks in a [`HybridRleDecoder`] as long as all skipped chunks do not include
+/// more than `num_values_to_skip` values.
+#[inline(always)]
+fn optional_skip_whole_chunks(
+    values: &mut HybridRleDecoder<'_>,
+    validity: &mut BitMask<'_>,
+    num_rows_to_skip: &mut usize,
+    num_values_to_skip: &mut usize,
+) -> ParquetResult<()> {
+    if *num_values_to_skip == 0 {
+        return Ok(());
+    }
+
+    let mut total_num_skipped_values = 0;
+
+    loop {
+        let mut values_clone = values.clone();
+        let Some(chunk_len) = values_clone.next_chunk_length()? else {
+            break;
+        };
+        if *num_values_to_skip < chunk_len {
+            break;
+        }
+        *values = values_clone;
+        *num_values_to_skip -= chunk_len;
+        total_num_skipped_values += chunk_len;
+    }
+
+    if total_num_skipped_values > 0 {
+        let offset = validity
+            .nth_set_bit_idx(total_num_skipped_values - 1, 0)
+            .map_or(validity.len(), |v| v + 1);
+        *num_rows_to_skip -= offset;
+        validity.advance_by(offset);
+    }
+
+    Ok(())
+}