Further docs

apache · Jan 4, 2022 · 28228b2 · 28228b2
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commit 28228b2
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Showing 2 changed files with 12 additions and 2 deletions.
diff --git a/parquet/src/arrow/record_reader.rs b/parquet/src/arrow/record_reader.rs
@@ -45,6 +45,11 @@ pub type RecordReader<T> =
     GenericRecordReader<TypedBuffer<<T as DataType>::T>, ColumnValueDecoderImpl<T>>;
 
 #[doc(hidden)]
+/// A generic stateful column reader that delimits semantic records
+///
+/// This type is hidden from the docs, and relies on private traits with no
+/// public implementations. As such this type signature may be changed without
+/// breaking downstream users as it can only be constructed through type aliases
 pub struct GenericRecordReader<V, CV> {
     column_desc: ColumnDescPtr,
 

diff --git a/parquet/src/arrow/record_reader/buffer.rs b/parquet/src/arrow/record_reader/buffer.rs
@@ -162,8 +162,13 @@ pub trait ValuesBuffer: BufferQueue {
     /// Iterate through the indexes in `range` in reverse order, moving the value at each
     /// index to the next index returned by `rev_valid_position_iter`
     ///
-    /// It is guaranteed that the `i`th index returned by `rev_valid_position_iter` is greater
-    /// than or equal to `range.end - i - 1`
+    /// It is required that:
+    ///
+    /// - `rev_valid_position_iter` has at least `range.end - range.start` elements
+    /// - `rev_valid_position_iter` returns strictly monotonically decreasing values
+    /// - the `i`th index returned by `rev_valid_position_iter` is `>= range.end - i - 1`
+    ///
+    /// Implementations may panic or otherwise misbehave if this is not the case
     ///
     fn pad_nulls(
         &mut self,