aljaz/turso
1
0
Fork 0
mirror of https://github.com/aljazceru/turso.git synced 2026-02-06 16:54:23 +01:00
Code Issues Packages Projects Releases Wiki Activity

introduce additional condition for cells distribution in order to avoid almost empty pages

Browse Source
This commit is contained in:
Nikita Sivukhin
2025-02-09 19:26:03 +04:00
parent bc289d314a
commit 32b5b0d019
1 changed files with 9 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
core/storage/btree.rs
View File

@@ -1137,7 +1137,12 @@ impl BTreeCursor {
scratch_cells.insert(cell.index, to_static_buf(&cell.payload));
}
// amount of cells for pages involved in split (distributed with naive greedy approach)
// amount of cells for pages involved in split
// the algorithm accumulate cells in greedy manner with 2 conditions for split:
// 1. new cell will overflow single cell (accumulated + new > usable_space - header_size)
// 2. accumulated size already reach >50% of content_usable_size
// second condition is necessary, otherwise in case of small cells we will create a lot of almost empty pages
//
// if we have single overflow cell in a table leaf node - we still can have 3 split pages
//
// for example, if current page has 4 entries with size ~1/4 page size, and new cell has size ~page size
@@ -1149,7 +1154,9 @@ impl BTreeCursor {
let content_usable_space = usable_space - page_copy.header_size();
for scratch_cell in scratch_cells.iter() {
let cell_size = scratch_cell.len() + 2; // + cell pointer size (u16)
if last_page_cells_size + cell_size > content_usable_space {
if last_page_cells_size + cell_size > content_usable_space
|| 2 * last_page_cells_size > content_usable_space
{
split_pages_cells_count.push(last_page_cells_count);
last_page_cells_count = 0;
last_page_cells_size = 0;