improve comments

Author: alamb

datafusion/core/src/datasource/physical_plan/parquet/access_plan.rs

@@ -17,10 +17,10 @@
 
 use parquet::arrow::arrow_reader::RowSelection;
 
-/// Specifies a selection of row groups / rows within a ParquetFile to decode.
+/// Specifies a selection of rows and row groups within a ParquetFile to decode.
 ///
-/// This structure can limit the row groups and data pages a `ParquetExec` will
-/// read and decode.
+/// A `ParquetAccessPlan` is used to limits the row groups and data pages a `ParquetExec`
+/// will read and decode and this improve performance.
 ///
 /// Note that page level pruning based on ArrowPredicate is applied after all of
 /// these selections

datafusion/core/src/datasource/physical_plan/parquet/page_filter.rs

@@ -284,7 +284,7 @@ fn find_column_index(
 
 /// Intersects the [`RowSelector`]s
 ///
-/// For exampe, given:
+/// For example, given:
 /// * `RowSelector1: [ Skip(0~199), Read(200~299)]`
 /// * `RowSelector2: [ Skip(0~99), Read(100~249), Skip(250~299)]`
 ///