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new b8c2741491b Minor: refine row selection example more (#5850)
b8c2741491b is described below
commit b8c2741491ba5c3464010e023d390a34d037cd2d
Author: Andrew Lamb <[email protected]>
AuthorDate: Tue Jun 11 14:28:41 2024 -0400
Minor: refine row selection example more (#5850)
---
parquet/src/arrow/arrow_reader/mod.rs | 29 ++++++++++++++++++++++++-----
1 file changed, 24 insertions(+), 5 deletions(-)
diff --git a/parquet/src/arrow/arrow_reader/mod.rs
b/parquet/src/arrow/arrow_reader/mod.rs
index bbb1c079b16..793f79272c1 100644
--- a/parquet/src/arrow/arrow_reader/mod.rs
+++ b/parquet/src/arrow/arrow_reader/mod.rs
@@ -155,24 +155,43 @@ impl<T> ArrowReaderBuilder<T> {
///
/// # Example
///
- /// Given a parquet file with 3 row groups, and a row group filter of
- /// `[0, 2]`, in order to only scan rows 50-100 in row group 2:
+ /// Given a parquet file with 4 row groups, and a row group filter of `[0,
+ /// 2, 3]`, in order to scan rows 50-100 in row group 2 and rows 200-300 in
+ /// row group 3:
///
/// ```text
/// Row Group 0, 1000 rows (selected)
/// Row Group 1, 1000 rows (skipped)
/// Row Group 2, 1000 rows (selected, but want to only scan rows 50-100)
+ /// Row Group 3, 1000 rows (selected, but want to only scan rows 200-300)
/// ```
///
- /// You would pass the following [`RowSelection`]:
+ /// You could pass the following [`RowSelection`]:
///
/// ```text
/// Select 1000 (scan all rows in row group 0)
- /// Select 50-100 (scan rows 50-100 in row group 2)
+ /// Skip 50 (skip the first 50 rows in row group 2)
+ /// Select 50 (scan rows 50-100 in row group 2)
+ /// Skip 900 (skip the remaining rows in row group 2)
+ /// Skip 200 (skip the first 200 rows in row group 3)
+ /// Select 100 (scan rows 200-300 in row group 3)
+ /// Skip 700 (skip the remaining rows in row group 3)
/// ```
- ///
/// Note there is no entry for the (entirely) skipped row group 1.
///
+ /// Note you can represent the same selection with fewer entries. Instead
of
+ ///
+ /// ```text
+ /// Skip 900 (skip the remaining rows in row group 2)
+ /// Skip 200 (skip the first 200 rows in row group 3)
+ /// ```
+ ///
+ /// you could use
+ ///
+ /// ```text
+ /// Skip 1100 (skip the remaining 900 rows in row group 2 and the
first 200 rows in row group 3)
+ /// ```
+ ///
/// [`Index`]: crate::file::page_index::index::Index
pub fn with_row_selection(self, selection: RowSelection) -> Self {
Self {
