[Parquet]Optimize the performance in record reader

parquet/src/arrow/buffer/bit_util.rs

@@ -18,6 +18,7 @@
 use arrow_buffer::bit_chunk_iterator::UnalignedBitChunk;
 use std::ops::Range;
 
+#[allow(unused)]
 /// Counts the number of set bits in the provided range
 pub fn count_set_bits(bytes: &[u8], range: Range<usize>) -> usize {
     let unaligned = UnalignedBitChunk::new(bytes, range.start, range.end - range.start);

parquet/src/arrow/record_reader/definition_levels.rs

@@ -20,7 +20,6 @@ use arrow_buffer::Buffer;
 use arrow_buffer::bit_chunk_iterator::UnalignedBitChunk;
 use bytes::Bytes;
 
-use crate::arrow::buffer::bit_util::count_set_bits;
 use crate::basic::Encoding;
 use crate::column::reader::decoder::{
     ColumnLevelDecoder, DefinitionLevelDecoder, DefinitionLevelDecoderImpl,
@@ -169,10 +168,7 @@ impl DefinitionLevelDecoder for DefinitionLevelBufferDecoder {
             (BufferInner::Mask { nulls }, MaybePacked::Packed(decoder)) => {
                 assert_eq!(self.max_level, 1);
 
-                let start = nulls.len();
-                let levels_read = decoder.read(nulls, num_levels)?;
-
-                let values_read = count_set_bits(nulls.as_slice(), start..start + levels_read);
+                let (values_read, levels_read) = decoder.read(nulls, num_levels)?;
                 Ok((values_read, levels_read))
             }
             _ => unreachable!("inconsistent null mask"),
@@ -284,20 +280,31 @@ impl PackedDecoder {
         self.data_offset = 0;
     }
 
-    fn read(&mut self, buffer: &mut BooleanBufferBuilder, len: usize) -> Result<usize> {
-        let mut read = 0;
-        while read != len {
+    /// Reads up to `len` definition levels directly into a boolean bitmask.
+    ///
+    /// Returns a tuple of `(values_read, levels_read)`, where `values_read` counts the
+    /// number of `true` bits appended to `buffer`.
+    fn read(&mut self, buffer: &mut BooleanBufferBuilder, len: usize) -> Result<(usize, usize)> {
+        let mut levels_read = 0;
+        let mut values_read = 0;
+        while levels_read != len {
             if self.rle_left != 0 {
-                let to_read = self.rle_left.min(len - read);
+                let to_read = self.rle_left.min(len - levels_read);
                 buffer.append_n(to_read, self.rle_value);
                 self.rle_left -= to_read;
-                read += to_read;
+                if self.rle_value {
+                    values_read += to_read;
+                }
+                levels_read += to_read;
             } else if self.packed_count != self.packed_offset {
-                let to_read = (self.packed_count - self.packed_offset).min(len - read);
+                let to_read = (self.packed_count - self.packed_offset).min(len - levels_read);
                 let offset = self.data_offset * 8 + self.packed_offset;
                 buffer.append_packed_range(offset..offset + to_read, self.data.as_ref());
+                // Packed runs already encode bits densely; count the ones we just appended.
+                values_read +=
+                    UnalignedBitChunk::new(self.data.as_ref(), offset, to_read).count_ones();
                 self.packed_offset += to_read;
-                read += to_read;
+                levels_read += to_read;
 
                 if self.packed_offset == self.packed_count {
                     self.data_offset += self.packed_count / 8;
@@ -308,7 +315,7 @@ impl PackedDecoder {
                 self.next_rle_block()?
             }
         }
-        Ok(read)
+        Ok((values_read, levels_read))
     }
 
     /// Skips `level_num` definition levels
@@ -360,10 +367,14 @@ mod tests {
 
         let mut expected = BooleanBufferBuilder::new(len);
         let mut encoder = RleEncoder::new(1, 1024);
+        let mut expected_value_count = 0;
         for _ in 0..len {
             let bool = rng.random_bool(0.8);
             encoder.put(bool as u64);
             expected.append(bool);
+            if bool {
+                expected_value_count += 1;
+            }
         }
         assert_eq!(expected.len(), len);
 
@@ -373,18 +384,27 @@ mod tests {
 
         // Decode data in random length intervals
         let mut decoded = BooleanBufferBuilder::new(len);
+        // Track how many `true` bits we appended to validate the returned counts.
+        let mut decoded_value_count = 0;
         loop {
             let remaining = len - decoded.len();
             if remaining == 0 {
                 break;
             }
 
             let to_read = rng.random_range(1..=remaining);
-            decoder.read(&mut decoded, to_read).unwrap();
+            let offset = decoded.len();
+            let (values_read, levels_read) = decoder.read(&mut decoded, to_read).unwrap();
+            assert_eq!(levels_read, to_read);
+            decoded_value_count += values_read;
+            let expected_chunk_ones =
+                UnalignedBitChunk::new(expected.as_slice(), offset, levels_read).count_ones();
+            assert_eq!(values_read, expected_chunk_ones);
         }
 
         assert_eq!(decoded.len(), len);
         assert_eq!(decoded.as_slice(), expected.as_slice());
+        assert_eq!(decoded_value_count, expected_value_count);
     }
 
     #[test]
@@ -428,18 +448,23 @@ mod tests {
                 skip_level += skip_level_num
             } else {
                 let mut decoded = BooleanBufferBuilder::new(to_read_or_skip_level);
-                let read_level_num = decoder.read(&mut decoded, to_read_or_skip_level).unwrap();
+                let (read_value_num, read_level_num) =
+                    decoder.read(&mut decoded, to_read_or_skip_level).unwrap();
                 read_level += read_level_num;
+                read_value += read_value_num;
+                // Verify the per-chunk counts match the exact bits we compared below.
+                let mut chunk_value_count = 0;
                 for i in 0..read_level_num {
                     assert!(!decoded.is_empty());
                     //check each read bit
                     let read_bit = decoded.get_bit(i);
                     if read_bit {
-                        read_value += 1;
+                        chunk_value_count += 1;
                     }
                     let expect_bit = expected.get_bit(i + offset);
                     assert_eq!(read_bit, expect_bit);
                 }
+                assert_eq!(chunk_value_count, read_value_num);
             }
         }
         assert_eq!(read_level + skip_level, len);

parquet/src/column/reader/decoder.rs

@@ -15,8 +15,6 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use std::collections::HashMap;
-
 use bytes::Bytes;
 
 use crate::basic::Encoding;
@@ -68,9 +66,9 @@ pub trait RepetitionLevelDecoder: ColumnLevelDecoder {
 }
 
 pub trait DefinitionLevelDecoder: ColumnLevelDecoder {
-    /// Read up to `num_levels` definition levels into `out`
+    /// Read up to `num_levels` definition levels into `out`.
     ///
-    /// Returns the number of values skipped, and the number of levels skipped
+    /// Returns the number of values read, and the number of levels read.
     ///
     /// # Panics
     ///
@@ -81,9 +79,9 @@ pub trait DefinitionLevelDecoder: ColumnLevelDecoder {
         num_levels: usize,
     ) -> Result<(usize, usize)>;
 
-    /// Skips over `num_levels` definition levels
+    /// Skips over `num_levels` definition levels.
     ///
-    /// Returns the number of values skipped, and the number of levels skipped
+    /// Returns the number of values skipped, and the number of levels skipped.
     fn skip_def_levels(&mut self, num_levels: usize) -> Result<(usize, usize)>;
 }
 
@@ -136,14 +134,75 @@ pub trait ColumnValueDecoder {
     fn skip_values(&mut self, num_values: usize) -> Result<usize>;
 }
 
+/// Bucket-based storage for decoder instances keyed by `Encoding`.
+///
+/// This replaces `HashMap` lookups with direct indexing to avoid hashing overhead in the
+/// hot decoding paths.
+const ENCODING_SLOTS: usize = 10; // covers the encodings handled in `enc_slot`
+
+#[inline]
+fn enc_slot(e: Encoding) -> usize {
+    match e {
+        Encoding::PLAIN => 0,
+        Encoding::PLAIN_DICTIONARY => 2,
+        Encoding::RLE => 3,
+        #[allow(deprecated)]
+        Encoding::BIT_PACKED => 4,
+        Encoding::DELTA_BINARY_PACKED => 5,
+        Encoding::DELTA_LENGTH_BYTE_ARRAY => 6,
+        Encoding::DELTA_BYTE_ARRAY => 7,
+        Encoding::RLE_DICTIONARY => 8,
+        Encoding::BYTE_STREAM_SPLIT => 9,
+    }
+}
+
+/// Fixed-capacity storage for decoder instances keyed by Parquet encoding.
+struct DecoderBuckets<V> {
+    inner: [Option<V>; ENCODING_SLOTS],
+}
+
+impl<V> DecoderBuckets<V> {
+    #[inline]
+    fn new() -> Self {
+        Self {
+            inner: std::array::from_fn(|_| None),
+        }
+    }
+
+    #[inline]
+    fn contains_key(&self, e: Encoding) -> bool {
+        self.inner[enc_slot(e)].is_some()
+    }
+
+    #[inline]
+    fn get_mut(&mut self, e: Encoding) -> Option<&mut V> {
+        self.inner[enc_slot(e)].as_mut()
+    }
+
+    #[inline]
+    fn insert_and_get_mut(&mut self, e: Encoding, v: V) -> &mut V {
+        let slot = &mut self.inner[enc_slot(e)];
+        debug_assert!(slot.is_none());
+        *slot = Some(v);
+        slot.as_mut().unwrap()
+    }
+}
+
+impl<V> Default for DecoderBuckets<V> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 /// An implementation of [`ColumnValueDecoder`] for `[T::T]`
 pub struct ColumnValueDecoderImpl<T: DataType> {
     descr: ColumnDescPtr,
 
     current_encoding: Option<Encoding>,
 
-    // Cache of decoders for existing encodings
-    decoders: HashMap<Encoding, Box<dyn Decoder<T>>>,
+    /// Cache of decoders for existing encodings.
+    /// Uses `DecoderBuckets` instead of `HashMap` for predictable indexing.
+    decoders: DecoderBuckets<Box<dyn Decoder<T>>>,
 }
 
 impl<T: DataType> ColumnValueDecoder for ColumnValueDecoderImpl<T> {
@@ -153,7 +212,7 @@ impl<T: DataType> ColumnValueDecoder for ColumnValueDecoderImpl<T> {
         Self {
             descr: descr.clone(),
             current_encoding: None,
-            decoders: Default::default(),
+            decoders: DecoderBuckets::new(),
         }
     }
 
@@ -168,7 +227,7 @@ impl<T: DataType> ColumnValueDecoder for ColumnValueDecoderImpl<T> {
             encoding = Encoding::RLE_DICTIONARY
         }
 
-        if self.decoders.contains_key(&encoding) {
+        if self.decoders.contains_key(encoding) {
             return Err(general_err!("Column cannot have more than one dictionary"));
         }
 
@@ -178,7 +237,8 @@ impl<T: DataType> ColumnValueDecoder for ColumnValueDecoderImpl<T> {
 
             let mut decoder = DictDecoder::new();
             decoder.set_dict(Box::new(dictionary))?;
-            self.decoders.insert(encoding, Box::new(decoder));
+            self.decoders
+                .insert_and_get_mut(encoding, Box::new(decoder));
             Ok(())
         } else {
             Err(nyi_err!(
@@ -195,24 +255,20 @@ impl<T: DataType> ColumnValueDecoder for ColumnValueDecoderImpl<T> {
         num_levels: usize,
         num_values: Option<usize>,
     ) -> Result<()> {
-        use std::collections::hash_map::Entry;
-
         if encoding == Encoding::PLAIN_DICTIONARY {
             encoding = Encoding::RLE_DICTIONARY;
         }
 
         let decoder = if encoding == Encoding::RLE_DICTIONARY {
             self.decoders
-                .get_mut(&encoding)
+                .get_mut(encoding)
                 .expect("Decoder for dict should have been set")
         } else {
-            // Search cache for data page decoder
-            match self.decoders.entry(encoding) {
-                Entry::Occupied(e) => e.into_mut(),
-                Entry::Vacant(v) => {
-                    let data_decoder = get_decoder::<T>(self.descr.clone(), encoding)?;
-                    v.insert(data_decoder)
-                }
+            if let Some(decoder) = self.decoders.get_mut(encoding) {
+                decoder
+            } else {
+                let data_decoder = get_decoder::<T>(self.descr.clone(), encoding)?;
+                self.decoders.insert_and_get_mut(encoding, data_decoder)
             }
         };
 
@@ -228,7 +284,7 @@ impl<T: DataType> ColumnValueDecoder for ColumnValueDecoderImpl<T> {
 
         let current_decoder = self
             .decoders
-            .get_mut(&encoding)
+            .get_mut(encoding)
             .unwrap_or_else(|| panic!("decoder for encoding {encoding} should be set"));
 
         // TODO: Push vec into decoder (#5177)
@@ -246,7 +302,7 @@ impl<T: DataType> ColumnValueDecoder for ColumnValueDecoderImpl<T> {
 
         let current_decoder = self
             .decoders
-            .get_mut(&encoding)
+            .get_mut(encoding)
             .unwrap_or_else(|| panic!("decoder for encoding {encoding} should be set"));
 
         current_decoder.skip(num_values)