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fix negative free space after balance-shallower

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This commit is contained in:
TcMits
2025-04-14 14:25:18 +07:00
parent b3c2593980
commit ee660187dc
1 changed files with 27 additions and 10 deletions
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37
core/storage/btree.rs
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@@ -2451,24 +2451,41 @@ impl BTreeCursor {
rightmost_pointer,
);
let first_child_page = &pages_to_balance_new[0];
let first_child_contents = first_child_page.get_contents();
// TODO: vacuum support
if parent_is_root && parent_contents.cell_count() == 0 {
if parent_is_root
&& parent_contents.cell_count() == 0
// this check to make sure we are not having negative free space
&& parent_contents.offset
<= compute_free_space(first_child_contents, self.usable_space() as u16)
as usize
{
// From SQLite:
// The root page of the b-tree now contains no cells. The only sibling
// page is the right-child of the parent. Copy the contents of the
// child page into the parent, decreasing the overall height of the
// b-tree structure by one. This is described as the "balance-shallower"
// sub-algorithm in some documentation.
assert!(sibling_count_new == 1);
let parent_offset = if parent_page.get().id == 1 {
DATABASE_HEADER_SIZE
} else {
0
};
let child_page = &pages_to_balance_new[0];
let child_contents = child_page.get_contents();
let child_top = child_contents.cell_content_area() as usize;
// From SQLite:
// It is critical that the child page be defragmented before being
// copied into the parent, because if the parent is page 1 then it will
// by smaller than the child due to the database header, and so
// all the free space needs to be up front.
defragment_page(first_child_contents, self.usable_space() as u16);
let child_top = first_child_contents.cell_content_area() as usize;
let parent_buf = parent_contents.as_ptr();
let child_buf = child_contents.as_ptr();
let child_buf = first_child_contents.as_ptr();
let content_size = self.usable_space() - child_top;
// Copy cell contents
@@ -2478,17 +2495,17 @@ impl BTreeCursor {
// Copy header and pointer
// NOTE: don't use .cell_pointer_array_offset_and_size() because of different
// header size
let header_and_pointer_size =
child_contents.header_size() + child_contents.cell_pointer_array_size();
let header_and_pointer_size = first_child_contents.header_size()
+ first_child_contents.cell_pointer_array_size();
parent_buf[parent_offset..parent_offset + header_and_pointer_size]
.copy_from_slice(
&child_buf[child_contents.offset
..child_contents.offset + header_and_pointer_size],
&child_buf[first_child_contents.offset
..first_child_contents.offset + header_and_pointer_size],
);
self.stack.set_cell_index(0); // reset cell index, top is already parent
self.pager
.free_page(Some(child_page.clone()), child_page.get().id)?;
.free_page(Some(first_child_page.clone()), first_child_page.get().id)?;
}
// We have to free pages that are not used anymore