[GitHub] [arrow-rs] alamb commented on a diff in pull request #2116: Simplify null mask preservation in parquet reader

[GitBox <gi...@apache.org>]

alamb commented on code in PR #2116:
URL: https://github.com/apache/arrow-rs/pull/2116#discussion_r927056687


##########
parquet/src/column/reader/decoder.rs:
##########
@@ -277,25 +288,25 @@ enum LevelDecoderInner {
 impl ColumnLevelDecoder for ColumnLevelDecoderImpl {
     type Slice = [i16];
 
-    fn new(max_level: i16, encoding: Encoding, data: ByteBufferPtr) -> Self {
-        let bit_width = num_required_bits(max_level as u64);
+    fn set_data(&mut self, encoding: Encoding, data: ByteBufferPtr) {

Review Comment:
   I am not an expert in this area, but the new code structure seems to make sense to me



##########
parquet/src/arrow/array_reader/byte_array.rs:
##########
@@ -127,15 +124,11 @@ impl<I: OffsetSizeTrait + ScalarValue> ArrayReader for ByteArrayReader<I> {
     }
 
     fn get_def_levels(&self) -> Option<&[i16]> {
-        self.def_levels_buffer
-            .as_ref()
-            .map(|buf| buf.typed_data())
+        self.def_levels_buffer.as_ref().map(|buf| buf.typed_data())

Review Comment:
   it is not entirely clear to me why the formatting changed on these lines -- not that it is a bad change, but it seems like it wasn't a semantic change either 🤷 



##########
parquet/src/arrow/record_reader/mod.rs:
##########
@@ -76,33 +77,8 @@ where
 {
     /// Create a new [`GenericRecordReader`]
     pub fn new(desc: ColumnDescPtr) -> Self {
-        Self::new_with_options(desc, false)
-    }
-
-    /// Create a new [`GenericRecordReader`] with the ability to only generate the bitmask
-    ///
-    /// If `null_mask_only` is true only the null bitmask will be generated and
-    /// [`Self::consume_def_levels`] and [`Self::consume_rep_levels`] will always return `None`
-    ///
-    /// It is insufficient to solely check that that the max definition level is 1 as we
-    /// need there to be no nullable parent array that will required decoded definition levels
-    ///
-    /// In particular consider the case of:
-    ///
-    /// ```ignore
-    /// message nested {
-    ///   OPTIONAL Group group {
-    ///     REQUIRED INT32 leaf;
-    ///   }
-    /// }
-    /// ```
-    ///
-    /// The maximum definition level of leaf is 1, however, we still need to decode the
-    /// definition levels so that the parent group can be constructed correctly
-    ///
-    pub(crate) fn new_with_options(desc: ColumnDescPtr, null_mask_only: bool) -> Self {
         let def_levels = (desc.max_def_level() > 0)
-            .then(|| DefinitionLevelBuffer::new(&desc, null_mask_only));
+            .then(|| DefinitionLevelBuffer::new(&desc, packed_null_mask(&desc)));

Review Comment:
   Is this is the key change in this PR? that the decision to use a null mask is pushed down to this level?



##########
parquet/src/column/reader.rs:
##########
@@ -195,7 +195,6 @@ where
     ///
     /// `values` will be contiguously populated with the non-null values. Note that if the column
     /// is not required, this may be less than either `batch_size` or the number of levels read
-    #[inline]

Review Comment:
   as in "when you leave `inline` the benchmarks get slower"?



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