aiondb-buffer-pool

Buffer pool / page cache. Manages fixed-size 8 KiB pages in memory with clock-sweep eviction, dirty-page tracking, and a PageStore trait that decouples in-memory frames from the underlying page-backed file. Also bundles the on-disk B-Tree, variable-length B-Tree, heap, and free-space-map data structures that sit directly on top of the pool.

cargo

[dependencies]
aiondb-buffer-pool = { path = "../aiondb-buffer-pool" }

modules

module	purpose
`page`	`Page` frame, `PageId`, `PAGE_SIZE` constant.
`pool`	`BufferPool`, `BufferPoolConfig`, `PageStore` trait, in-memory and file backends.
`eviction`	`ClockSweep` eviction policy.
`flusher`	background dirty-page flusher (`BackgroundFlusher`, `FlusherConfig`, `FlusherHandle`).
`metrics`	counters and snapshot type.
`disk`	`FilePageStore` page-file backend.
`disk_btree`	fixed-key disk B-Tree (`DiskBTree`, config, stats).
`disk_var_btree`	variable-length-key disk B-Tree.
`disk_heap`	tuple heap with vacuum support.
`heap_page`	low-level heap page format (`HeapPage`, `ItemId`).
`free_space_map`	per-relation free-space map.

key types

type	role
`BufferPool`	the in-memory page cache; striped page-load locks, clock-sweep, metrics.
`BufferPoolConfig`	`num_frames`, `max_dirty_pages`, flusher poll interval, flush batch size, flag for the background flusher.
`BufferPoolError`, `BufferPoolResult<T>`	error and result aliases.
`PageGuard<'a>`	RAII pin handle returned by `fetch_page` / `new_page`.
`Page`, `PageId`, `PAGE_SIZE`	the page frame and its identifier.
`PageStore`	trait every backing store implements (`read_page`, `write_page`, `allocate_page`, `reset_relation`, `sync`).
`MemoryPageStore`	in-memory `PageStore`, used for tests.
`FilePageStore`	file-backed `PageStore` for production.
`ClockSweep`	the eviction policy.
`BackgroundFlusher`, `FlusherConfig`, `FlusherHandle`	background dirty-page flushing.
`BufferPoolMetrics`, `BufferPoolMetricsSnapshot`	hit/miss/eviction counters.
`DiskBTree`, `DiskBTreeConfig`, `DiskBTreeStats`	fixed-key B-Tree on top of the pool.
`DiskVarBTree`, `DiskVarBTreeConfig`, `DiskVarBTreeStats`, `VarEntry`	variable-key B-Tree.
`DiskHeap`, `TupleLocation`, `VacuumStats`	heap of tuples with vacuum.
`HeapPage`, `HeapPageRef`, `ItemId`	heap page layout.
`FreeSpaceMap`	per-relation free-space tracker.

example

use std::sync::Arc;
use aiondb_buffer_pool::{BufferPool, MemoryPageStore, PageId};

let store = Arc::new(MemoryPageStore::new());
let pool = BufferPool::new(64, store);

let guard = pool.new_page(/* relation_id = */ 1).expect("allocate page");
let page_id: PageId = guard.page_id();
{
    let mut page = guard.write();
    page.data_mut()[..5].copy_from_slice(b"hello");
}
drop(guard);

pool.flush_page(page_id).expect("flush");
let _snapshot = pool.metrics();