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simplify balance_root

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This commit is contained in:
Pere Diaz Bou
2025-02-16 18:01:33 +01:00
parent f9d979575b
commit 177dbcd403
1 changed files with 51 additions and 59 deletions
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110
core/storage/btree.rs
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@@ -1071,6 +1071,7 @@ impl BTreeCursor {
.borrow_mut()
.push(cell_buf.to_vec());
log::trace!(
tracing::trace!(
"dropping divider cell from parent cell_idx={} count={}",
cell_idx,
parent_contents.cell_count()
@@ -1468,73 +1469,64 @@ impl BTreeCursor {
};
let offset = if is_page_1 { DATABASE_HEADER_SIZE } else { 0 };
let new_root_page = self.allocate_page(PageType::TableInterior, offset);
{
let current_root = self.stack.top();
let current_root_contents = current_root.get().contents.as_ref().unwrap();
let new_root_page_contents = new_root_page.get().contents.as_mut().unwrap();
if is_page_1 {
// Copy header
let current_root_buf = current_root_contents.as_ptr();
let new_root_buf = new_root_page_contents.as_ptr();
new_root_buf[0..DATABASE_HEADER_SIZE]
.copy_from_slice(&current_root_buf[0..DATABASE_HEADER_SIZE]);
}
// point new root right child to previous root
new_root_page_contents.write_u32(
PAGE_HEADER_OFFSET_RIGHTMOST_PTR,
current_root.get().id as u32,
);
new_root_page_contents.write_u16(PAGE_HEADER_OFFSET_CELL_COUNT, 0);
}
let root = self.stack.top();
let root_contents = root.get_contents();
let child = self.allocate_page(root_contents.page_type(), 0);
/* swap split page buffer with new root buffer so we don't have to update page idx */
{
let (root_id, child_id, child) = {
let page_ref = self.stack.top();
let child = page_ref.clone();
tracing::debug!(
"Balancing root. root={}, rightmost={}",
root.get().id,
child.get().id
);
// Swap the entire Page structs
std::mem::swap(&mut child.get().id, &mut new_root_page.get().id);
// TODO:: shift bytes by offset to left on child because now child has offset 100
// and header bytes
// Also change the offset of page
//
if is_page_1 {
// Remove header from child and set offset to 0
let contents = child.get().contents.as_mut().unwrap();
let (cell_pointer_offset, _) = contents.cell_pointer_array_offset_and_size();
// change cell pointers
for cell_idx in 0..contents.cell_count() {
let cell_pointer_offset = cell_pointer_offset + (2 * cell_idx);
let pc = contents.read_u16_no_offset(cell_pointer_offset);
contents.write_u16_no_offset(cell_pointer_offset, pc as u16);
}
self.pager.add_dirty(root.get().id);
self.pager.add_dirty(child.get().id);
contents.offset = 0;
let buf = contents.as_ptr();
buf.copy_within(DATABASE_HEADER_SIZE.., 0);
}
let root_buf = root_contents.as_ptr();
let child_contents = child.get_contents();
let child_buf = child_contents.as_ptr();
let (root_pointer_start, root_pointer_len) =
root_contents.cell_pointer_array_offset_and_size();
let (child_pointer_start, _) = child.get_contents().cell_pointer_array_offset_and_size();
self.pager.add_dirty(new_root_page.get().id);
self.pager.add_dirty(child.get().id);
(new_root_page.get().id, child.get().id, child)
};
let top = root_contents.cell_content_area() as usize;
debug!("Balancing root. root={}, rightmost={}", root_id, child_id);
let root = new_root_page.clone();
// 1. Modify child
// Copy pointers
child_buf[child_pointer_start..child_pointer_start + root_pointer_len]
.copy_from_slice(&root_buf[root_pointer_start..root_pointer_start + root_pointer_len]);
// Copy cell contents
child_buf[top..].copy_from_slice(&root_buf[top..]);
// Copy header
child_buf[0..root_contents.header_size()]
.copy_from_slice(&root_buf[offset..offset + root_contents.header_size()]);
// Copy overflow cells
child_contents.overflow_cells = root_contents.overflow_cells.clone();
self.root_page = root_id;
self.stack.clear();
self.stack.push(root.clone());
// advance in order to maintain semantics
self.stack.advance();
self.stack.push(child.clone());
// 2. Modify root
let new_root_page_type = match root_contents.page_type() {
PageType::IndexLeaf => PageType::IndexInterior,
PageType::TableLeaf => PageType::TableInterior,
_ => unreachable!("invalid root non leaf page type"),
} as u8;
// set new page type
root_contents.write_u8(PAGE_HEADER_OFFSET_PAGE_TYPE, new_root_page_type);
root_contents.write_u32(PAGE_HEADER_OFFSET_RIGHTMOST_PTR, child.get().id as u32);
root_contents.write_u16(
PAGE_HEADER_OFFSET_CELL_CONTENT_AREA,
self.usable_space() as u16,
);
root_contents.write_u16(PAGE_HEADER_OFFSET_CELL_COUNT, 0);
root_contents.write_u16(PAGE_HEADER_OFFSET_FIRST_FREEBLOCK, 0);
self.pager.put_loaded_page(root_id, root);
self.pager.put_loaded_page(child_id, child);
}
root_contents.write_u8(PAGE_HEADER_OFFSET_FRAGMENTED_BYTES_COUNT, 0);
root_contents.overflow_cells.clear();
self.root_page = root.get().id;
self.stack.clear();
self.stack.push(root.clone());
self.stack.advance();
self.stack.push(child.clone());
}
/// Allocate a new page to the btree via the pager.