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btree: add MAX_NEW_PAGES_AFTER_BALANCE constant and use it

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This commit is contained in:
Jussi Saurio
2025-07-10 15:24:32 +03:00
parent 10d301c53c
commit 6ff13113ce
1 changed files with 16 additions and 10 deletions
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26
core/storage/btree.rs
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@@ -101,6 +101,9 @@ pub mod offset {
/// assumed that the database is corrupt.
pub const BTCURSOR_MAX_DEPTH: usize = 20;
/// We only need maximum 5 pages to balance 3 pages, because we can guarantee that cells from 3 pages will fit in 5 pages.
pub const MAX_NEW_PAGES_AFTER_BALANCE: usize = 5;
/// Evaluate a Result<CursorResult<T>>, if IO return IO.
macro_rules! return_if_io {
($expr:expr) => {
@@ -2493,8 +2496,8 @@ impl BTreeCursor {
// The count includes: all cells and overflow cells from the sibling pages, and divider cells from the parent page,
// excluding the rightmost divider, which will not be dropped from the parent; instead it will be updated at the end.
let mut total_cells_to_redistribute = 0;
// We only need maximum 5 pages to balance 3 pages, because we can guarantee that cells from 3 pages will fit in 5 pages.
let mut pages_to_balance_new: [Option<BTreePage>; 5] = [const { None }; 5];
let mut pages_to_balance_new: [Option<BTreePage>; MAX_NEW_PAGES_AFTER_BALANCE] =
[const { None }; MAX_NEW_PAGES_AFTER_BALANCE];
for i in (0..balance_info.sibling_count).rev() {
let sibling_page = balance_info.pages_to_balance[i].as_ref().unwrap();
let sibling_page = sibling_page.get();
@@ -2537,14 +2540,15 @@ impl BTreeCursor {
/* 2. Initialize CellArray with all the cells used for distribution, this includes divider cells if !leaf. */
let mut cell_array = CellArray {
cell_payloads: Vec::with_capacity(total_cells_to_redistribute),
cell_count_per_page_cumulative: [0; 5],
cell_count_per_page_cumulative: [0; MAX_NEW_PAGES_AFTER_BALANCE],
};
let cells_capacity_start = cell_array.cell_payloads.capacity();
let mut total_cells_inserted = 0;
// This is otherwise identical to CellArray.cell_count_per_page_cumulative,
// but we exclusively track what the prefix sums were _before_ we started redistributing cells.
let mut old_cell_count_per_page_cumulative: [u16; 5] = [0; 5];
let mut old_cell_count_per_page_cumulative: [u16; MAX_NEW_PAGES_AFTER_BALANCE] =
[0; MAX_NEW_PAGES_AFTER_BALANCE];
let page_type = balance_info.pages_to_balance[0]
.as_ref()
@@ -2637,7 +2641,8 @@ impl BTreeCursor {
validate_cells_after_insertion(&cell_array, is_table_leaf);
/* 3. Initiliaze current size of every page including overflow cells and divider cells that might be included. */
let mut new_page_sizes: [i64; 5] = [0; 5];
let mut new_page_sizes: [i64; MAX_NEW_PAGES_AFTER_BALANCE] =
[0; MAX_NEW_PAGES_AFTER_BALANCE];
let header_size = if is_leaf {
LEAF_PAGE_HEADER_SIZE_BYTES
} else {
@@ -2902,7 +2907,8 @@ impl BTreeCursor {
// Reassign page numbers in increasing order
{
let mut page_numbers: [usize; 5] = [0; 5];
let mut page_numbers: [usize; MAX_NEW_PAGES_AFTER_BALANCE] =
[0; MAX_NEW_PAGES_AFTER_BALANCE];
for (i, page) in pages_to_balance_new
.iter()
.take(sibling_count_new)
@@ -3114,7 +3120,7 @@ impl BTreeCursor {
** upwards pass simply processes pages that were missed on the downward
** pass.
*/
let mut done = [false; 5];
let mut done = [false; MAX_NEW_PAGES_AFTER_BALANCE];
for i in (1 - sibling_count_new as i64)..sibling_count_new as i64 {
// As mentioned above, we do two passes over the pages:
// 1. Downward pass: Process pages in decreasing order
@@ -3314,7 +3320,7 @@ impl BTreeCursor {
parent_page: &BTreePage,
balance_info: &mut BalanceInfo,
parent_contents: &mut PageContent,
pages_to_balance_new: [Option<BTreePage>; 5],
pages_to_balance_new: [Option<BTreePage>; MAX_NEW_PAGES_AFTER_BALANCE],
page_type: PageType,
leaf_data: bool,
mut cells_debug: Vec<Vec<u8>>,
@@ -5503,7 +5509,7 @@ struct CellArray {
/// Prefix sum of cells in each page.
/// For example, if three pages have 1, 2, and 3 cells, respectively,
/// then cell_count_per_page_cumulative will be [1, 3, 6].
cell_count_per_page_cumulative: [u16; 5],
cell_count_per_page_cumulative: [u16; MAX_NEW_PAGES_AFTER_BALANCE],
}
impl CellArray {
@@ -8381,7 +8387,7 @@ mod tests {
for _ in 0..ITERATIONS {
let mut cell_array = CellArray {
cell_payloads: Vec::new(),
cell_count_per_page_cumulative: [0; 5],
cell_count_per_page_cumulative: [0; MAX_NEW_PAGES_AFTER_BALANCE],
};
let mut cells_cloned = Vec::new();
let (pager, _, _, _) = empty_btree();