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//! Maintenance walks: rekey under a new epoch and reachable-page collection.
use crate::Result;
use crate::errors::PagedbError;
use crate::pager::format::page_kind::PageKind;
use crate::vfs::Vfs;
use crate::btree::leaf::{Leaf, LeafValue};
use crate::btree::node::{NodeKind, read_header};
use crate::btree::{internal, overflow};
use super::core::BTree;
impl<V: Vfs> BTree<V> {
/// Walk every page reachable from `self.root_page_id` (internal nodes,
/// leaves, overflow chains) and rewrite each one under the pager's current
/// `mk_epoch`. Pages are read via epoch-routing (so old-epoch pages decrypt
/// correctly) and marked dirty so the next flush re-seals them under the
/// new epoch.
///
/// Returns the count of pages touched.
pub async fn rekey_walk(&self) -> Result<u64> {
if self.root_page_id == 0 {
return Ok(0);
}
let mut stack: Vec<u64> = vec![self.root_page_id];
let mut count: u64 = 0;
while let Some(page_id) = stack.pop() {
// Determine kind by reading node header via epoch-routed path.
// Try leaf page kind first; on AAD mismatch try internal.
let (is_leaf, body_bytes) = {
match self
.pager
.read_main_page(page_id, self.realm_id, PageKind::BTreeLeaf)
.await
{
Ok(g) => {
let body = g.body();
let header = read_header(&body)?;
let is_leaf = header.kind == NodeKind::Leaf;
(is_leaf, body.to_vec())
}
Err(PagedbError::ChecksumFailure) => {
let g = self
.pager
.read_main_page(page_id, self.realm_id, PageKind::BTreeInternal)
.await?;
let body = g.body();
(false, body.to_vec())
}
Err(e) => return Err(e),
}
};
if is_leaf {
// Collect overflow chains referenced by this leaf.
let leaf = Leaf::decode(&body_bytes)?;
for (_k, v) in &leaf.records {
if let LeafValue::Overflow {
root_page_id: ov_root,
..
} = v
{
// Rewrite root page (v2 OverflowRoot or v1 Overflow).
let root_info =
overflow::read_root_page(&self.pager, self.realm_id, *ov_root).await?;
let root_kind = if root_info.is_v2 {
PageKind::OverflowRoot
} else {
PageKind::Overflow
};
self.pager
.rewrite_page_under_current_epoch(*ov_root, self.realm_id, root_kind)
.await?;
count += 1;
// Walk and rewrite chain pages (always PageKind::Overflow).
let mut next = root_info.next;
while next != 0 {
let ov_guard = self
.pager
.read_main_page(next, self.realm_id, PageKind::Overflow)
.await?;
let ov_body = ov_guard.body();
let (ov_next, _) = overflow::decode_overflow(&ov_body)?;
drop(ov_guard);
self.pager
.rewrite_page_under_current_epoch(
next,
self.realm_id,
PageKind::Overflow,
)
.await?;
count += 1;
next = ov_next;
}
}
}
// Rewrite the leaf page.
self.pager
.rewrite_page_under_current_epoch(page_id, self.realm_id, PageKind::BTreeLeaf)
.await?;
count += 1;
} else {
// Internal node: push children onto stack.
let internal = internal::Internal::decode(&body_bytes)?;
stack.push(internal.leftmost_child);
for entry in &internal.entries {
stack.push(entry.right_child);
}
// Rewrite the internal page.
self.pager
.rewrite_page_under_current_epoch(
page_id,
self.realm_id,
PageKind::BTreeInternal,
)
.await?;
count += 1;
}
}
Ok(count)
}
/// Collect all page IDs reachable from this tree's root (internal nodes,
/// leaves, overflow chains) into `out`. Used by the deep-walk integrity
/// checker to identify orphan pages.
#[allow(clippy::too_many_lines)]
pub async fn collect_all_page_ids(
&self,
out: &mut std::collections::BTreeSet<u64>,
) -> Result<()> {
if self.root_page_id == 0 {
return Ok(());
}
let mut stack: Vec<u64> = vec![self.root_page_id];
while let Some(page_id) = stack.pop() {
if !out.insert(page_id) {
// Already visited.
continue;
}
let (is_leaf, body_bytes) = {
match self
.pager
.read_main_page(page_id, self.realm_id, PageKind::BTreeLeaf)
.await
{
Ok(g) => {
let body = g.body();
let header = read_header(&body)?;
let is_leaf = header.kind == NodeKind::Leaf;
(is_leaf, body.to_vec())
}
Err(PagedbError::ChecksumFailure) => {
match self
.pager
.read_main_page(page_id, self.realm_id, PageKind::BTreeInternal)
.await
{
Ok(g) => (false, g.body().to_vec()),
Err(_) => continue, // unreadable — best effort
}
}
Err(_) => continue,
}
};
if is_leaf {
let Ok(leaf) = Leaf::decode(&body_bytes) else {
continue;
};
for (_k, v) in &leaf.records {
if let LeafValue::Overflow {
root_page_id: ov_root,
..
} = v
{
self.collect_overflow_chain(*ov_root, out).await;
}
}
} else {
// Internal node: push child page IDs.
let Ok(internal) = internal::Internal::decode(&body_bytes) else {
continue;
};
if internal.leftmost_child != 0 {
stack.push(internal.leftmost_child);
}
for entry in &internal.entries {
if entry.right_child != 0 {
stack.push(entry.right_child);
}
}
}
}
Ok(())
}
/// Walk an overflow chain starting at `root` and insert all page IDs into
/// `out`. Best-effort: stops on any read failure.
async fn collect_overflow_chain(&self, root: u64, out: &mut std::collections::BTreeSet<u64>) {
let mut first = true;
let mut chain_id = root;
while chain_id != 0 {
if !out.insert(chain_id) {
break;
}
let kind = if first {
first = false;
PageKind::OverflowRoot
} else {
PageKind::Overflow
};
let g = match self
.pager
.read_main_page(chain_id, self.realm_id, kind)
.await
{
Ok(g) => g,
Err(PagedbError::ChecksumFailure) => {
match self
.pager
.read_main_page(chain_id, self.realm_id, PageKind::Overflow)
.await
{
Ok(g) => g,
Err(_) => break,
}
}
Err(_) => break,
};
let body = g.body();
if body.len() < 8 {
break;
}
let mut b = [0u8; 8];
b.copy_from_slice(&body[..8]);
chain_id = u64::from_le_bytes(b);
}
}
}