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Minor: Add arrow-rs ticket reference and turn some comments into docstrings #4088

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Nov 3, 2022
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Minor: Add arrow-rs ticket reference and turn some comments into docstrings #4088

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108 changes: 56 additions & 52 deletions datafusion/core/src/physical_plan/file_format/parquet.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -585,51 +585,53 @@ impl FileOpener for ParquetOpener {
}
}

// For example:
// > ┏━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━
// > ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┃
// > ┃ ┌──────────────┐ │ ┌──────────────┐ │ ┃
// > ┃ │ │ │ │ │ │ ┃
// > ┃ │ │ │ │ Page │ │
// > │ │ │ │ │ 3 │ ┃
// > ┃ │ │ │ │ min: "A" │ │ ┃
// > ┃ │ │ │ │ │ max: "C" │ ┃
// > ┃ │ Page │ │ │ first_row: 0 │ │
// > │ │ 1 │ │ │ │ ┃
// > ┃ │ min: 10 │ │ └──────────────┘ │ ┃
// > ┃ │ │ max: 20 │ │ ┌──────────────┐ ┃
// > ┃ │ first_row: 0 │ │ │ │ │
// > │ │ │ │ │ Page │ ┃
// > ┃ │ │ │ │ 4 │ │ ┃
// > ┃ │ │ │ │ │ min: "D" │ ┃
// > ┃ │ │ │ │ max: "G" │ │
// > │ │ │ │ │first_row: 100│ ┃
// > ┃ └──────────────┘ │ │ │ │ ┃
// > ┃ │ ┌──────────────┐ │ │ │ ┃
// > ┃ │ │ │ └──────────────┘ │
// > │ │ Page │ │ ┌──────────────┐ ┃
// > ┃ │ 2 │ │ │ │ │ ┃
// > ┃ │ │ min: 30 │ │ │ Page │ ┃
// > ┃ │ max: 40 │ │ │ 5 │ │
// > │ │first_row: 200│ │ │ min: "H" │ ┃
// > ┃ │ │ │ │ max: "Z" │ │ ┃
// > ┃ │ │ │ │ │first_row: 250│ ┃
// > ┃ └──────────────┘ │ │ │ │
// > │ │ └──────────────┘ ┃
// > ┃ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┃
// > ┃ ColumnChunk ColumnChunk ┃
// > ┃ A B
// > ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━┛
// >
// > Total rows: 300
//
// Given the predicate 'A > 35 AND B = "F"':
// using `extract_page_index_push_down_predicates` get two single column predicate:
// Using 'A > 35': could get RowSelector1: [ Skip(0~199), Read(200~299)]
// Using B = "F": could get RowSelector2: [ Skip(0~99), Read(100~249), Skip(250~299)]
//
// As the Final selection is the intersection of each columns RowSelectors:
// final_selection:[ Skip(0~199), Read(200~249), Skip(250~299)]
/// For example:
/// ```text
/// ┏━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━
/// ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┃
/// ┃ ┌──────────────┐ │ ┌──────────────┐ │ ┃
/// ┃ │ │ │ │ │ │ ┃
/// ┃ │ │ │ │ Page │ │
/// │ │ │ │ │ 3 │ ┃
/// ┃ │ │ │ │ min: "A" │ │ ┃
/// ┃ │ │ │ │ │ max: "C" │ ┃
/// ┃ │ Page │ │ │ first_row: 0 │ │
/// │ │ 1 │ │ │ │ ┃
/// ┃ │ min: 10 │ │ └──────────────┘ │ ┃
/// ┃ │ │ max: 20 │ │ ┌──────────────┐ ┃
/// ┃ │ first_row: 0 │ │ │ │ │
/// │ │ │ │ │ Page │ ┃
/// ┃ │ │ │ │ 4 │ │ ┃
/// ┃ │ │ │ │ │ min: "D" │ ┃
/// ┃ │ │ │ │ max: "G" │ │
/// │ │ │ │ │first_row: 100│ ┃
/// ┃ └──────────────┘ │ │ │ │ ┃
/// ┃ │ ┌──────────────┐ │ │ │ ┃
/// ┃ │ │ │ └──────────────┘ │
/// │ │ Page │ │ ┌──────────────┐ ┃
/// ┃ │ 2 │ │ │ │ │ ┃
/// ┃ │ │ min: 30 │ │ │ Page │ ┃
/// ┃ │ max: 40 │ │ │ 5 │ │
/// │ │first_row: 200│ │ │ min: "H" │ ┃
/// ┃ │ │ │ │ max: "Z" │ │ ┃
/// ┃ │ │ │ │ │first_row: 250│ ┃
/// ┃ └──────────────┘ │ │ │ │
/// │ │ └──────────────┘ ┃
/// ┃ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┃
/// ┃ ColumnChunk ColumnChunk ┃
/// ┃ A B
/// ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━━ ━━┛
///
/// Total rows: 300
/// ```
///
/// Given the predicate 'A > 35 AND B = "F"':
/// using `extract_page_index_push_down_predicates` get two single column predicate:
/// Using 'A > 35': could get `RowSelector1: [ Skip(0~199), Read(200~299)]`
/// Using B = "F": could get `RowSelector2: [ Skip(0~99), Read(100~249), Skip(250~299)]`
///
/// As the Final selection is the intersection of each columns `RowSelectors:
/// final_selection:[ Skip(0~199), Read(200~249), Skip(250~299)]`
fn combine_multi_col_selection(
row_selections: VecDeque<Vec<RowSelector>>,
) -> Vec<RowSelector> {
Expand All @@ -639,13 +641,15 @@ fn combine_multi_col_selection(
.unwrap()
}

// combine two `RowSelection` return the intersection
// For example:
// self: NNYYYYNNY
// other: NYNNNNNNY
//
// returned: NNNNNNNNY
// set `need_combine` true will combine result: Select(2) + Select(1) + Skip(2) -> Select(3) + Skip(2)
/// combine two `RowSelection` return the intersection
/// For example:
/// self: NNYYYYNNY
/// other: NYNNNNNNY
///
/// returned: NNNNNNNNY
/// set `need_combine` true will combine result: Select(2) + Select(1) + Skip(2) -> Select(3) + Skip(2)
///
/// Move to arrow-rs: https://github.com/apache/arrow-rs/issues/3003
pub(crate) fn intersect_row_selection(
left: Vec<RowSelector>,
right: Vec<RowSelector>,
Expand Down