Line data Source code
1 : //!
2 : //! Simple on-disk B-tree implementation
3 : //!
4 : //! This is used as the index structure within image and delta layers
5 : //!
6 : //! Features:
7 : //! - Fixed-width keys
8 : //! - Fixed-width values (VALUE_SZ)
9 : //! - The tree is created in a bulk operation. Insert/deletion after creation
10 : //! is not supported
11 : //! - page-oriented
12 : //!
13 : //! TODO:
14 : //! - maybe something like an Adaptive Radix Tree would be more efficient?
15 : //! - the values stored by image and delta layers are offsets into the file,
16 : //! and they are in monotonically increasing order. Prefix compression would
17 : //! be very useful for them, too.
18 : //! - An Iterator interface would be more convenient for the callers than the
19 : //! 'visit' function
20 : //!
21 : use std::cmp::Ordering;
22 : use std::iter::Rev;
23 : use std::ops::{Range, RangeInclusive};
24 : use std::{io, result};
25 :
26 : use async_stream::try_stream;
27 : use byteorder::{BE, ReadBytesExt};
28 : use bytes::BufMut;
29 : use either::Either;
30 : use futures::{Stream, StreamExt};
31 : use hex;
32 : use thiserror::Error;
33 : use tracing::error;
34 :
35 : use crate::context::RequestContext;
36 : use crate::tenant::block_io::{BlockReader, BlockWriter};
37 : use crate::virtual_file::{IoBuffer, IoBufferMut, owned_buffers_io::write::Buffer};
38 :
39 : // The maximum size of a value stored in the B-tree. 5 bytes is enough currently.
40 : pub const VALUE_SZ: usize = 5;
41 : pub const MAX_VALUE: u64 = 0x007f_ffff_ffff;
42 :
43 : pub const PAGE_SZ: usize = 8192;
44 :
45 : #[derive(Clone, Copy, Debug)]
46 : struct Value([u8; VALUE_SZ]);
47 :
48 : impl Value {
49 4557504 : fn from_slice(slice: &[u8]) -> Value {
50 4557504 : let mut b = [0u8; VALUE_SZ];
51 4557504 : b.copy_from_slice(slice);
52 4557504 : Value(b)
53 4557504 : }
54 :
55 3374389 : fn from_u64(x: u64) -> Value {
56 3374389 : assert!(x <= 0x007f_ffff_ffff);
57 3374389 : Value([
58 3374389 : (x >> 32) as u8,
59 3374389 : (x >> 24) as u8,
60 3374389 : (x >> 16) as u8,
61 3374389 : (x >> 8) as u8,
62 3374389 : x as u8,
63 3374389 : ])
64 3374389 : }
65 :
66 6243 : fn from_blknum(x: u32) -> Value {
67 6243 : Value([
68 6243 : 0x80,
69 6243 : (x >> 24) as u8,
70 6243 : (x >> 16) as u8,
71 6243 : (x >> 8) as u8,
72 6243 : x as u8,
73 6243 : ])
74 6243 : }
75 :
76 : #[allow(dead_code)]
77 0 : fn is_offset(self) -> bool {
78 0 : self.0[0] & 0x80 != 0
79 0 : }
80 :
81 4227905 : fn to_u64(self) -> u64 {
82 4227905 : let b = &self.0;
83 4227905 : ((b[0] as u64) << 32)
84 4227905 : | ((b[1] as u64) << 24)
85 4227905 : | ((b[2] as u64) << 16)
86 4227905 : | ((b[3] as u64) << 8)
87 4227905 : | b[4] as u64
88 4227905 : }
89 :
90 326587 : fn to_blknum(self) -> u32 {
91 326587 : let b = &self.0;
92 326587 : assert!(b[0] == 0x80);
93 326587 : ((b[1] as u32) << 24) | ((b[2] as u32) << 16) | ((b[3] as u32) << 8) | b[4] as u32
94 326587 : }
95 : }
96 :
97 : #[derive(Error, Debug)]
98 : pub enum DiskBtreeError {
99 : #[error("Attempt to append a value that is too large {0} > {}", MAX_VALUE)]
100 : AppendOverflow(u64),
101 :
102 : #[error("Unsorted input: key {key:?} is <= last_key {last_key:?}")]
103 : UnsortedInput { key: Box<[u8]>, last_key: Box<[u8]> },
104 :
105 : #[error("Could not push to new leaf node")]
106 : FailedToPushToNewLeafNode,
107 :
108 : #[error("IoError: {0}")]
109 : Io(#[from] io::Error),
110 : }
111 :
112 : pub type Result<T> = result::Result<T, DiskBtreeError>;
113 :
114 : /// This is the on-disk representation.
115 : struct OnDiskNode<'a, const L: usize> {
116 : // Fixed-width fields
117 : num_children: u16,
118 : level: u8,
119 : prefix_len: u8,
120 : suffix_len: u8,
121 :
122 : // Variable-length fields. These are stored on-disk after the fixed-width
123 : // fields, in this order. In the in-memory representation, these point to
124 : // the right parts in the page buffer.
125 : prefix: &'a [u8],
126 : keys: &'a [u8],
127 : values: &'a [u8],
128 : }
129 :
130 : impl<const L: usize> OnDiskNode<'_, L> {
131 : ///
132 : /// Interpret a PAGE_SZ page as a node.
133 : ///
134 790071 : fn deparse(buf: &[u8]) -> Result<OnDiskNode<L>> {
135 790071 : let mut cursor = std::io::Cursor::new(buf);
136 790071 : let num_children = cursor.read_u16::<BE>()?;
137 790071 : let level = cursor.read_u8()?;
138 790071 : let prefix_len = cursor.read_u8()?;
139 790071 : let suffix_len = cursor.read_u8()?;
140 :
141 790071 : let mut off = cursor.position();
142 790071 : let prefix_off = off as usize;
143 790071 : off += prefix_len as u64;
144 790071 :
145 790071 : let keys_off = off as usize;
146 790071 : let keys_len = num_children as usize * suffix_len as usize;
147 790071 : off += keys_len as u64;
148 790071 :
149 790071 : let values_off = off as usize;
150 790071 : let values_len = num_children as usize * VALUE_SZ;
151 790071 : //off += values_len as u64;
152 790071 :
153 790071 : let prefix = &buf[prefix_off..prefix_off + prefix_len as usize];
154 790071 : let keys = &buf[keys_off..keys_off + keys_len];
155 790071 : let values = &buf[values_off..values_off + values_len];
156 790071 :
157 790071 : Ok(OnDiskNode {
158 790071 : num_children,
159 790071 : level,
160 790071 : prefix_len,
161 790071 : suffix_len,
162 790071 : prefix,
163 790071 : keys,
164 790071 : values,
165 790071 : })
166 790071 : }
167 :
168 : ///
169 : /// Read a value at 'idx'
170 : ///
171 4557504 : fn value(&self, idx: usize) -> Value {
172 4557504 : let value_off = idx * VALUE_SZ;
173 4557504 : let value_slice = &self.values[value_off..value_off + VALUE_SZ];
174 4557504 : Value::from_slice(value_slice)
175 4557504 : }
176 :
177 676171 : fn binary_search(
178 676171 : &self,
179 676171 : search_key: &[u8; L],
180 676171 : keybuf: &mut [u8],
181 676171 : ) -> result::Result<usize, usize> {
182 676171 : let mut size = self.num_children as usize;
183 676171 : let mut low = 0;
184 676171 : let mut high = size;
185 5161822 : while low < high {
186 4623194 : let mid = low + size / 2;
187 4623194 :
188 4623194 : let key_off = mid * self.suffix_len as usize;
189 4623194 : let suffix = &self.keys[key_off..key_off + self.suffix_len as usize];
190 4623194 : // Does this match?
191 4623194 : keybuf[self.prefix_len as usize..].copy_from_slice(suffix);
192 4623194 :
193 4623194 : let cmp = keybuf[..].cmp(search_key);
194 4623194 :
195 4623194 : if cmp == Ordering::Less {
196 2920475 : low = mid + 1;
197 2920475 : } else if cmp == Ordering::Greater {
198 1565176 : high = mid;
199 1565176 : } else {
200 137543 : return Ok(mid);
201 : }
202 4485651 : size = high - low;
203 : }
204 538628 : Err(low)
205 676171 : }
206 : }
207 :
208 : ///
209 : /// Public reader object, to search the tree.
210 : ///
211 : #[derive(Clone)]
212 : pub struct DiskBtreeReader<R, const L: usize>
213 : where
214 : R: BlockReader,
215 : {
216 : start_blk: u32,
217 : root_blk: u32,
218 : reader: R,
219 : }
220 :
221 : #[derive(Clone, Copy, Debug, PartialEq, Eq)]
222 : pub enum VisitDirection {
223 : Forwards,
224 : Backwards,
225 : }
226 :
227 : impl<R, const L: usize> DiskBtreeReader<R, L>
228 : where
229 : R: BlockReader,
230 : {
231 134079 : pub fn new(start_blk: u32, root_blk: u32, reader: R) -> Self {
232 134079 : DiskBtreeReader {
233 134079 : start_blk,
234 134079 : root_blk,
235 134079 : reader,
236 134079 : }
237 134079 : }
238 :
239 : ///
240 : /// Read the value for given key. Returns the value, or None if it doesn't exist.
241 : ///
242 201628 : pub async fn get(&self, search_key: &[u8; L], ctx: &RequestContext) -> Result<Option<u64>> {
243 201628 : let mut result: Option<u64> = None;
244 201628 : self.visit(
245 201628 : search_key,
246 201628 : VisitDirection::Forwards,
247 201628 : |key, value| {
248 101616 : if key == search_key {
249 100613 : result = Some(value);
250 100613 : }
251 101616 : false
252 201628 : },
253 201628 : ctx,
254 201628 : )
255 201628 : .await?;
256 201628 : Ok(result)
257 201628 : }
258 :
259 352 : pub fn iter<'a>(self, start_key: &'a [u8; L], ctx: &'a RequestContext) -> DiskBtreeIterator<'a>
260 352 : where
261 352 : R: 'a + Send,
262 352 : {
263 352 : DiskBtreeIterator {
264 352 : stream: Box::pin(self.into_stream(start_key, ctx)),
265 352 : }
266 352 : }
267 :
268 : /// Return a stream which yields all key, value pairs from the index
269 : /// starting from the first key greater or equal to `start_key`.
270 : ///
271 : /// Note 1: that this is a copy of [`Self::visit`].
272 : /// TODO: Once the sequential read path is removed this will become
273 : /// the only index traversal method.
274 : ///
275 : /// Note 2: this function used to take `&self` but it now consumes `self`. This is due to
276 : /// the lifetime constraints of the reader and the stream / iterator it creates. Using `&self`
277 : /// requires the reader to be present when the stream is used, and this creates a lifetime
278 : /// dependency between the reader and the stream. Now if we want to create an iterator that
279 : /// holds the stream, someone will need to keep a reference to the reader, which is inconvenient
280 : /// to use from the image/delta layer APIs.
281 : ///
282 : /// Feel free to add the `&self` variant back if it's necessary.
283 143730 : pub fn into_stream<'a>(
284 143730 : self,
285 143730 : start_key: &'a [u8; L],
286 143730 : ctx: &'a RequestContext,
287 143730 : ) -> impl Stream<Item = std::result::Result<(Vec<u8>, u64), DiskBtreeError>> + 'a
288 143730 : where
289 143730 : R: 'a,
290 143730 : {
291 143730 : try_stream! {
292 143730 : let mut stack = Vec::new();
293 143730 : stack.push((self.root_blk, None));
294 143730 : let block_cursor = self.reader.block_cursor();
295 143730 : let mut node_buf = [0_u8; PAGE_SZ];
296 143730 : while let Some((node_blknum, opt_iter)) = stack.pop() {
297 143730 : // Read the node, through the PS PageCache, into local variable `node_buf`.
298 143730 : // We could keep the page cache read guard alive, but, at the time of writing,
299 143730 : // we run quite small PS PageCache s => can't risk running out of
300 143730 : // PageCache space because this stream isn't consumed fast enough.
301 143730 : let page_read_guard = block_cursor
302 143730 : .read_blk(self.start_blk + node_blknum, ctx)
303 143730 : .await?;
304 143730 : node_buf.copy_from_slice(page_read_guard.as_ref());
305 143730 : drop(page_read_guard); // drop page cache read guard early
306 143730 :
307 143730 : let node = OnDiskNode::deparse(&node_buf)?;
308 143730 : let prefix_len = node.prefix_len as usize;
309 143730 : let suffix_len = node.suffix_len as usize;
310 143730 :
311 143730 : assert!(node.num_children > 0);
312 143730 :
313 143730 : let mut keybuf = Vec::new();
314 143730 : keybuf.extend(node.prefix);
315 143730 : keybuf.resize(prefix_len + suffix_len, 0);
316 143730 :
317 143730 : let mut iter: Either<Range<usize>, Rev<RangeInclusive<usize>>> = if let Some(iter) = opt_iter {
318 143730 : iter
319 143730 : } else {
320 143730 : // Locate the first match
321 143730 : let idx = match node.binary_search(start_key, keybuf.as_mut_slice()) {
322 143730 : Ok(idx) => idx,
323 143730 : Err(idx) => {
324 143730 : if node.level == 0 {
325 143730 : // Imagine that the node contains the following keys:
326 143730 : //
327 143730 : // 1
328 143730 : // 3 <-- idx
329 143730 : // 5
330 143730 : //
331 143730 : // If the search key is '2' and there is exact match,
332 143730 : // the binary search would return the index of key
333 143730 : // '3'. That's cool, '3' is the first key to return.
334 143730 : idx
335 143730 : } else {
336 143730 : // This is an internal page, so each key represents a lower
337 143730 : // bound for what's in the child page. If there is no exact
338 143730 : // match, we have to return the *previous* entry.
339 143730 : //
340 143730 : // 1 <-- return this
341 143730 : // 3 <-- idx
342 143730 : // 5
343 143730 : idx.saturating_sub(1)
344 143730 : }
345 143730 : }
346 143730 : };
347 143730 : Either::Left(idx..node.num_children.into())
348 143730 : };
349 143730 :
350 143730 :
351 143730 : // idx points to the first match now. Keep going from there
352 143730 : while let Some(idx) = iter.next() {
353 143730 : let key_off = idx * suffix_len;
354 143730 : let suffix = &node.keys[key_off..key_off + suffix_len];
355 143730 : keybuf[prefix_len..].copy_from_slice(suffix);
356 143730 : let value = node.value(idx);
357 143730 : #[allow(clippy::collapsible_if)]
358 143730 : if node.level == 0 {
359 143730 : // leaf
360 143730 : yield (keybuf.clone(), value.to_u64());
361 143730 : } else {
362 143730 : stack.push((node_blknum, Some(iter)));
363 143730 : stack.push((value.to_blknum(), None));
364 143730 : break;
365 143730 : }
366 143730 : }
367 143730 : }
368 143730 : }
369 143730 : }
370 :
371 : ///
372 : /// Scan the tree, starting from 'search_key', in the given direction. 'visitor'
373 : /// will be called for every key >= 'search_key' (or <= 'search_key', if scanning
374 : /// backwards)
375 : ///
376 205858 : pub async fn visit<V>(
377 205858 : &self,
378 205858 : search_key: &[u8; L],
379 205858 : dir: VisitDirection,
380 205858 : mut visitor: V,
381 205858 : ctx: &RequestContext,
382 205858 : ) -> Result<bool>
383 205858 : where
384 205858 : V: FnMut(&[u8], u64) -> bool,
385 205858 : {
386 205858 : let mut stack = Vec::new();
387 205858 : stack.push((self.root_blk, None));
388 205858 : let block_cursor = self.reader.block_cursor();
389 609629 : while let Some((node_blknum, opt_iter)) = stack.pop() {
390 : // Locate the node.
391 509362 : let node_buf = block_cursor
392 509362 : .read_blk(self.start_blk + node_blknum, ctx)
393 509362 : .await?;
394 :
395 509362 : let node = OnDiskNode::deparse(node_buf.as_ref())?;
396 509362 : let prefix_len = node.prefix_len as usize;
397 509362 : let suffix_len = node.suffix_len as usize;
398 509362 :
399 509362 : assert!(node.num_children > 0);
400 :
401 509362 : let mut keybuf = Vec::new();
402 509362 : keybuf.extend(node.prefix);
403 509362 : keybuf.resize(prefix_len + suffix_len, 0);
404 :
405 509362 : let mut iter = if let Some(iter) = opt_iter {
406 101949 : iter
407 407413 : } else if dir == VisitDirection::Forwards {
408 : // Locate the first match
409 405400 : let idx = match node.binary_search(search_key, keybuf.as_mut_slice()) {
410 101717 : Ok(idx) => idx,
411 303683 : Err(idx) => {
412 303683 : if node.level == 0 {
413 : // Imagine that the node contains the following keys:
414 : //
415 : // 1
416 : // 3 <-- idx
417 : // 5
418 : //
419 : // If the search key is '2' and there is exact match,
420 : // the binary search would return the index of key
421 : // '3'. That's cool, '3' is the first key to return.
422 104058 : idx
423 : } else {
424 : // This is an internal page, so each key represents a lower
425 : // bound for what's in the child page. If there is no exact
426 : // match, we have to return the *previous* entry.
427 : //
428 : // 1 <-- return this
429 : // 3 <-- idx
430 : // 5
431 199625 : idx.saturating_sub(1)
432 : }
433 : }
434 : };
435 405400 : Either::Left(idx..node.num_children.into())
436 : } else {
437 2013 : let idx = match node.binary_search(search_key, keybuf.as_mut_slice()) {
438 1001 : Ok(idx) => {
439 1001 : // Exact match. That's the first entry to return, and walk
440 1001 : // backwards from there.
441 1001 : idx
442 : }
443 1012 : Err(idx) => {
444 : // No exact match. The binary search returned the index of the
445 : // first key that's > search_key. Back off by one, and walk
446 : // backwards from there.
447 1012 : if let Some(idx) = idx.checked_sub(1) {
448 1010 : idx
449 : } else {
450 2 : return Ok(false);
451 : }
452 : }
453 : };
454 2011 : Either::Right((0..=idx).rev())
455 : };
456 :
457 : // idx points to the first match now. Keep going from there
458 1581337 : while let Some(idx) = iter.next() {
459 1379121 : let key_off = idx * suffix_len;
460 1379121 : let suffix = &node.keys[key_off..key_off + suffix_len];
461 1379121 : keybuf[prefix_len..].copy_from_slice(suffix);
462 1379121 : let value = node.value(idx);
463 1379121 : #[allow(clippy::collapsible_if)]
464 1379121 : if node.level == 0 {
465 : // leaf
466 1177566 : if !visitor(&keybuf, value.to_u64()) {
467 105589 : return Ok(false);
468 1071977 : }
469 : } else {
470 201555 : stack.push((node_blknum, Some(iter)));
471 201555 : stack.push((value.to_blknum(), None));
472 201555 : break;
473 : }
474 : }
475 : }
476 100267 : Ok(true)
477 205858 : }
478 :
479 : #[allow(dead_code)]
480 5 : pub async fn dump(&self, ctx: &RequestContext) -> Result<()> {
481 5 : let mut stack = Vec::new();
482 5 :
483 5 : stack.push((self.root_blk, String::new(), 0, 0, 0));
484 5 :
485 5 : let block_cursor = self.reader.block_cursor();
486 :
487 3021 : while let Some((blknum, path, depth, child_idx, key_off)) = stack.pop() {
488 3016 : let blk = block_cursor.read_blk(self.start_blk + blknum, ctx).await?;
489 3016 : let buf: &[u8] = blk.as_ref();
490 3016 : let node = OnDiskNode::<L>::deparse(buf)?;
491 :
492 3016 : if child_idx == 0 {
493 9 : print!("{:indent$}", "", indent = depth * 2);
494 9 : let path_prefix = stack
495 9 : .iter()
496 9 : .map(|(_blknum, path, ..)| path.as_str())
497 9 : .collect::<String>();
498 9 : println!(
499 9 : "blk #{blknum}: path {path_prefix}{path}: prefix {}, suffix_len {}",
500 9 : hex::encode(node.prefix),
501 9 : node.suffix_len
502 9 : );
503 3007 : }
504 :
505 3016 : if child_idx + 1 < node.num_children {
506 3007 : let key_off = key_off + node.suffix_len as usize;
507 3007 : stack.push((blknum, path.clone(), depth, child_idx + 1, key_off));
508 3007 : }
509 3016 : let key = &node.keys[key_off..key_off + node.suffix_len as usize];
510 3016 : let val = node.value(child_idx as usize);
511 3016 :
512 3016 : print!("{:indent$}", "", indent = depth * 2 + 2);
513 3016 : println!("{}: {}", hex::encode(key), hex::encode(val.0));
514 3016 :
515 3016 : if node.level > 0 {
516 4 : stack.push((val.to_blknum(), hex::encode(node.prefix), depth + 1, 0, 0));
517 3012 : }
518 : }
519 5 : Ok(())
520 5 : }
521 : }
522 :
523 : pub struct DiskBtreeIterator<'a> {
524 : #[allow(clippy::type_complexity)]
525 : stream: std::pin::Pin<
526 : Box<dyn Stream<Item = std::result::Result<(Vec<u8>, u64), DiskBtreeError>> + 'a + Send>,
527 : >,
528 : }
529 :
530 : impl DiskBtreeIterator<'_> {
531 1161958 : pub async fn next(&mut self) -> Option<std::result::Result<(Vec<u8>, u64), DiskBtreeError>> {
532 1161958 : self.stream.next().await
533 1161958 : }
534 : }
535 :
536 : ///
537 : /// Public builder object, for creating a new tree.
538 : ///
539 : /// Usage: Create a builder object by calling 'new', load all the data into the
540 : /// tree by calling 'append' for each key-value pair, and then call 'finish'
541 : ///
542 : /// 'L' is the key length in bytes
543 : pub struct DiskBtreeBuilder<W, const L: usize>
544 : where
545 : W: BlockWriter,
546 : {
547 : writer: W,
548 :
549 : ///
550 : /// `stack[0]` is the current root page, `stack.last()` is the leaf.
551 : ///
552 : /// We maintain the length of the stack to be always greater than zero.
553 : /// Two exceptions are:
554 : /// 1. `Self::flush_node`. The method will push the new node if it extracted the last one.
555 : /// So because other methods cannot see the intermediate state invariant still holds.
556 : /// 2. `Self::finish`. It consumes self and does not return it back,
557 : /// which means that this is where the structure is destroyed.
558 : /// Thus stack of zero length cannot be observed by other methods.
559 : stack: Vec<BuildNode<L>>,
560 :
561 : /// Last key that was appended to the tree. Used to sanity check that append
562 : /// is called in increasing key order.
563 : last_key: Option<[u8; L]>,
564 : }
565 :
566 : impl<W, const L: usize> DiskBtreeBuilder<W, L>
567 : where
568 : W: BlockWriter,
569 : {
570 1058 : pub fn new(writer: W) -> Self {
571 1058 : DiskBtreeBuilder {
572 1058 : writer,
573 1058 : last_key: None,
574 1058 : stack: vec![BuildNode::new(0)],
575 1058 : }
576 1058 : }
577 :
578 3374390 : pub fn append(&mut self, key: &[u8; L], value: u64) -> Result<()> {
579 3374390 : if value > MAX_VALUE {
580 0 : return Err(DiskBtreeError::AppendOverflow(value));
581 3374390 : }
582 3374390 : if let Some(last_key) = &self.last_key {
583 3373444 : if key <= last_key {
584 1 : return Err(DiskBtreeError::UnsortedInput {
585 1 : key: key.as_slice().into(),
586 1 : last_key: last_key.as_slice().into(),
587 1 : });
588 3373443 : }
589 946 : }
590 3374389 : self.last_key = Some(*key);
591 3374389 :
592 3374389 : self.append_internal(key, Value::from_u64(value))
593 3374390 : }
594 :
595 3380632 : fn append_internal(&mut self, key: &[u8; L], value: Value) -> Result<()> {
596 3380632 : // Try to append to the current leaf buffer
597 3380632 : let last = self
598 3380632 : .stack
599 3380632 : .last_mut()
600 3380632 : .expect("should always have at least one item");
601 3380632 : let level = last.level;
602 3380632 : if last.push(key, value) {
603 3368769 : return Ok(());
604 11863 : }
605 11863 :
606 11863 : // It did not fit. Try to compress, and if it succeeds to make
607 11863 : // some room on the node, try appending to it again.
608 11863 : #[allow(clippy::collapsible_if)]
609 11863 : if last.compress() {
610 6025 : if last.push(key, value) {
611 6022 : return Ok(());
612 3 : }
613 5838 : }
614 :
615 : // Could not append to the current leaf. Flush it and create a new one.
616 5841 : self.flush_node()?;
617 :
618 : // Replace the node we flushed with an empty one and append the new
619 : // key to it.
620 5841 : let mut last = BuildNode::new(level);
621 5841 : if !last.push(key, value) {
622 0 : return Err(DiskBtreeError::FailedToPushToNewLeafNode);
623 5841 : }
624 5841 :
625 5841 : self.stack.push(last);
626 5841 :
627 5841 : Ok(())
628 3380632 : }
629 :
630 : /// Flush the bottommost node in the stack to disk. Appends a downlink to its parent,
631 : /// and recursively flushes the parent too, if it becomes full. If the root page becomes full,
632 : /// creates a new root page, increasing the height of the tree.
633 6243 : fn flush_node(&mut self) -> Result<()> {
634 6243 : // Get the current bottommost node in the stack and flush it to disk.
635 6243 : let last = self
636 6243 : .stack
637 6243 : .pop()
638 6243 : .expect("should always have at least one item");
639 6243 : let buf = last.pack();
640 6243 : let downlink_key = last.first_key();
641 6243 : let downlink_ptr = self.writer.write_blk(buf)?;
642 :
643 : // Append the downlink to the parent. If there is no parent, ie. this was the root page,
644 : // create a new root page, increasing the height of the tree.
645 6243 : if self.stack.is_empty() {
646 402 : self.stack.push(BuildNode::new(last.level + 1));
647 5841 : }
648 6243 : self.append_internal(&downlink_key, Value::from_blknum(downlink_ptr))
649 6243 : }
650 :
651 : ///
652 : /// Flushes everything to disk, and returns the block number of the root page.
653 : /// The caller must store the root block number "out-of-band", and pass it
654 : /// to the DiskBtreeReader::new() when you want to read the tree again.
655 : /// (In the image and delta layers, it is stored in the beginning of the file,
656 : /// in the summary header)
657 : ///
658 921 : pub fn finish(mut self) -> Result<(u32, W)> {
659 : // flush all levels, except the root.
660 1323 : while self.stack.len() > 1 {
661 402 : self.flush_node()?;
662 : }
663 :
664 921 : let root = self
665 921 : .stack
666 921 : .first()
667 921 : .expect("by the check above we left one item there");
668 921 : let buf = root.pack();
669 921 : let root_blknum = self.writer.write_blk(buf)?;
670 :
671 921 : Ok((root_blknum, self.writer))
672 921 : }
673 :
674 1023833 : pub fn borrow_writer(&self) -> &W {
675 1023833 : &self.writer
676 1023833 : }
677 : }
678 :
679 : ///
680 : /// BuildNode represesnts an incomplete page that we are appending to.
681 : ///
682 : #[derive(Clone, Debug)]
683 : struct BuildNode<const L: usize> {
684 : num_children: u16,
685 : level: u8,
686 : prefix: Vec<u8>,
687 : suffix_len: usize,
688 :
689 : keys: Vec<u8>,
690 : values: Vec<u8>,
691 :
692 : size: usize, // physical size of this node, if it was written to disk like this
693 : }
694 :
695 : const NODE_SIZE: usize = PAGE_SZ;
696 :
697 : const NODE_HDR_SIZE: usize = 2 + 1 + 1 + 1;
698 :
699 : impl<const L: usize> BuildNode<L> {
700 7301 : fn new(level: u8) -> Self {
701 7301 : BuildNode {
702 7301 : num_children: 0,
703 7301 : level,
704 7301 : prefix: Vec::new(),
705 7301 : suffix_len: 0,
706 7301 : keys: Vec::new(),
707 7301 : values: Vec::new(),
708 7301 : size: NODE_HDR_SIZE,
709 7301 : }
710 7301 : }
711 :
712 : /// Try to append a key-value pair to this node. Returns 'true' on
713 : /// success, 'false' if the page was full or the key was
714 : /// incompatible with the prefix of the existing keys.
715 3392498 : fn push(&mut self, key: &[u8; L], value: Value) -> bool {
716 3392498 : // If we have already performed prefix-compression on the page,
717 3392498 : // check that the incoming key has the same prefix.
718 3392498 : if self.num_children > 0 {
719 : // does the prefix allow it?
720 3385309 : if !key.starts_with(&self.prefix) {
721 104 : return false;
722 3385205 : }
723 7189 : } else {
724 7189 : self.suffix_len = key.len();
725 7189 : }
726 :
727 : // Is the node too full?
728 3392394 : if self.size + self.suffix_len + VALUE_SZ >= NODE_SIZE {
729 11762 : return false;
730 3380632 : }
731 3380632 :
732 3380632 : // All clear
733 3380632 : self.num_children += 1;
734 3380632 : self.keys.extend(&key[self.prefix.len()..]);
735 3380632 : self.values.extend(value.0);
736 3380632 :
737 3380632 : assert!(self.keys.len() == self.num_children as usize * self.suffix_len);
738 3380632 : assert!(self.values.len() == self.num_children as usize * VALUE_SZ);
739 :
740 3380632 : self.size += self.suffix_len + VALUE_SZ;
741 3380632 :
742 3380632 : true
743 3392498 : }
744 :
745 : ///
746 : /// Perform prefix-compression.
747 : ///
748 : /// Returns 'true' on success, 'false' if no compression was possible.
749 : ///
750 11863 : fn compress(&mut self) -> bool {
751 11863 : let first_suffix = self.first_suffix();
752 11863 : let last_suffix = self.last_suffix();
753 11863 :
754 11863 : // Find the common prefix among all keys
755 11863 : let mut prefix_len = 0;
756 107962 : while prefix_len < self.suffix_len {
757 107962 : if first_suffix[prefix_len] != last_suffix[prefix_len] {
758 11863 : break;
759 96099 : }
760 96099 : prefix_len += 1;
761 : }
762 11863 : if prefix_len == 0 {
763 5838 : return false;
764 6025 : }
765 6025 :
766 6025 : // Can compress. Rewrite the keys without the common prefix.
767 6025 : self.prefix.extend(&self.keys[..prefix_len]);
768 6025 :
769 6025 : let mut new_keys = Vec::new();
770 6025 : let mut key_off = 0;
771 1612004 : while key_off < self.keys.len() {
772 1605979 : let next_key_off = key_off + self.suffix_len;
773 1605979 : new_keys.extend(&self.keys[key_off + prefix_len..next_key_off]);
774 1605979 : key_off = next_key_off;
775 1605979 : }
776 6025 : self.keys = new_keys;
777 6025 : self.suffix_len -= prefix_len;
778 6025 :
779 6025 : self.size -= prefix_len * self.num_children as usize;
780 6025 : self.size += prefix_len;
781 6025 :
782 6025 : assert!(self.keys.len() == self.num_children as usize * self.suffix_len);
783 6025 : assert!(self.values.len() == self.num_children as usize * VALUE_SZ);
784 :
785 6025 : true
786 11863 : }
787 :
788 : ///
789 : /// Serialize the node to on-disk format.
790 : ///
791 7164 : fn pack(&self) -> IoBuffer {
792 7164 : assert!(self.keys.len() == self.num_children as usize * self.suffix_len);
793 7164 : assert!(self.values.len() == self.num_children as usize * VALUE_SZ);
794 7164 : assert!(self.num_children > 0);
795 :
796 7164 : let mut buf = IoBufferMut::with_capacity(PAGE_SZ);
797 7164 :
798 7164 : buf.put_u16(self.num_children);
799 7164 : buf.put_u8(self.level);
800 7164 : buf.put_u8(self.prefix.len() as u8);
801 7164 : buf.put_u8(self.suffix_len as u8);
802 7164 : buf.put(&self.prefix[..]);
803 7164 : buf.put(&self.keys[..]);
804 7164 : buf.put(&self.values[..]);
805 7164 :
806 7164 : assert!(buf.len() == self.size);
807 :
808 7164 : assert!(buf.len() <= PAGE_SZ);
809 7164 : buf.extend_with(0, PAGE_SZ - buf.len());
810 7164 : buf.freeze()
811 7164 : }
812 :
813 18106 : fn first_suffix(&self) -> &[u8] {
814 18106 : &self.keys[..self.suffix_len]
815 18106 : }
816 11863 : fn last_suffix(&self) -> &[u8] {
817 11863 : &self.keys[self.keys.len() - self.suffix_len..]
818 11863 : }
819 :
820 : /// Return the full first key of the page, including the prefix
821 6243 : fn first_key(&self) -> [u8; L] {
822 6243 : let mut key = [0u8; L];
823 6243 : key[..self.prefix.len()].copy_from_slice(&self.prefix);
824 6243 : key[self.prefix.len()..].copy_from_slice(self.first_suffix());
825 6243 : key
826 6243 : }
827 : }
828 :
829 : #[cfg(test)]
830 : pub(crate) mod tests {
831 : use std::collections::BTreeMap;
832 : use std::sync::atomic::{AtomicUsize, Ordering};
833 :
834 : use rand::Rng;
835 :
836 : use super::*;
837 : use crate::context::DownloadBehavior;
838 : use crate::task_mgr::TaskKind;
839 : use crate::tenant::block_io::{BlockCursor, BlockLease, BlockReaderRef};
840 :
841 : #[derive(Clone, Default)]
842 : pub(crate) struct TestDisk {
843 : blocks: Vec<IoBuffer>,
844 : }
845 : impl TestDisk {
846 5 : fn new() -> Self {
847 5 : Self::default()
848 5 : }
849 508484 : pub(crate) fn read_blk(&self, blknum: u32) -> io::Result<BlockLease> {
850 508484 : let mut buf = [0u8; PAGE_SZ];
851 508484 : buf.copy_from_slice(&self.blocks[blknum as usize]);
852 508484 : Ok(std::sync::Arc::new(buf).into())
853 508484 : }
854 : }
855 : impl BlockReader for TestDisk {
856 205661 : fn block_cursor(&self) -> BlockCursor<'_> {
857 205661 : BlockCursor::new(BlockReaderRef::TestDisk(self))
858 205661 : }
859 : }
860 : impl BlockWriter for &mut TestDisk {
861 108 : fn write_blk(&mut self, buf: IoBuffer) -> io::Result<u32> {
862 108 : let blknum = self.blocks.len();
863 108 : self.blocks.push(buf);
864 108 : Ok(blknum as u32)
865 108 : }
866 : }
867 :
868 : #[tokio::test]
869 1 : async fn basic() -> Result<()> {
870 1 : let mut disk = TestDisk::new();
871 1 : let mut writer = DiskBtreeBuilder::<_, 6>::new(&mut disk);
872 1 :
873 1 : let ctx =
874 1 : RequestContext::new(TaskKind::UnitTest, DownloadBehavior::Error).with_scope_unit_test();
875 1 :
876 1 : let all_keys: Vec<&[u8; 6]> = vec![
877 1 : b"xaaaaa", b"xaaaba", b"xaaaca", b"xabaaa", b"xababa", b"xabaca", b"xabada", b"xabadb",
878 1 : ];
879 1 : let all_data: Vec<(&[u8; 6], u64)> = all_keys
880 1 : .iter()
881 1 : .enumerate()
882 8 : .map(|(idx, key)| (*key, idx as u64))
883 1 : .collect();
884 8 : for (key, val) in all_data.iter() {
885 8 : writer.append(key, *val)?;
886 1 : }
887 1 :
888 1 : let (root_offset, _writer) = writer.finish()?;
889 1 :
890 1 : let reader = DiskBtreeReader::new(0, root_offset, disk);
891 1 :
892 1 : reader.dump(&ctx).await?;
893 1 :
894 1 : // Test the `get` function on all the keys.
895 8 : for (key, val) in all_data.iter() {
896 8 : assert_eq!(reader.get(key, &ctx).await?, Some(*val));
897 1 : }
898 1 : // And on some keys that don't exist
899 1 : assert_eq!(reader.get(b"aaaaaa", &ctx).await?, None);
900 1 : assert_eq!(reader.get(b"zzzzzz", &ctx).await?, None);
901 1 : assert_eq!(reader.get(b"xaaabx", &ctx).await?, None);
902 1 :
903 1 : // Test search with `visit` function
904 1 : let search_key = b"xabaaa";
905 1 : let expected: Vec<(Vec<u8>, u64)> = all_data
906 1 : .iter()
907 8 : .filter(|(key, _value)| key[..] >= search_key[..])
908 5 : .map(|(key, value)| (key.to_vec(), *value))
909 1 : .collect();
910 1 :
911 1 : let mut data = Vec::new();
912 1 : reader
913 1 : .visit(
914 1 : search_key,
915 1 : VisitDirection::Forwards,
916 5 : |key, value| {
917 5 : data.push((key.to_vec(), value));
918 5 : true
919 5 : },
920 1 : &ctx,
921 1 : )
922 1 : .await?;
923 1 : assert_eq!(data, expected);
924 1 :
925 1 : // Test a backwards scan
926 1 : let mut expected: Vec<(Vec<u8>, u64)> = all_data
927 1 : .iter()
928 8 : .filter(|(key, _value)| key[..] <= search_key[..])
929 4 : .map(|(key, value)| (key.to_vec(), *value))
930 1 : .collect();
931 1 : expected.reverse();
932 1 : let mut data = Vec::new();
933 1 : reader
934 1 : .visit(
935 1 : search_key,
936 1 : VisitDirection::Backwards,
937 4 : |key, value| {
938 4 : data.push((key.to_vec(), value));
939 4 : true
940 4 : },
941 1 : &ctx,
942 1 : )
943 1 : .await?;
944 1 : assert_eq!(data, expected);
945 1 :
946 1 : // Backward scan where nothing matches
947 1 : reader
948 1 : .visit(
949 1 : b"aaaaaa",
950 1 : VisitDirection::Backwards,
951 1 : |key, value| {
952 0 : panic!("found unexpected key {}: {}", hex::encode(key), value);
953 1 : },
954 1 : &ctx,
955 1 : )
956 1 : .await?;
957 1 :
958 1 : // Full scan
959 1 : let expected: Vec<(Vec<u8>, u64)> = all_data
960 1 : .iter()
961 8 : .map(|(key, value)| (key.to_vec(), *value))
962 1 : .collect();
963 1 : let mut data = Vec::new();
964 1 : reader
965 1 : .visit(
966 1 : &[0u8; 6],
967 1 : VisitDirection::Forwards,
968 8 : |key, value| {
969 8 : data.push((key.to_vec(), value));
970 8 : true
971 8 : },
972 1 : &ctx,
973 1 : )
974 1 : .await?;
975 1 : assert_eq!(data, expected);
976 1 :
977 1 : Ok(())
978 1 : }
979 :
980 : #[tokio::test]
981 1 : async fn lots_of_keys() -> Result<()> {
982 1 : let mut disk = TestDisk::new();
983 1 : let mut writer = DiskBtreeBuilder::<_, 8>::new(&mut disk);
984 1 : let ctx =
985 1 : RequestContext::new(TaskKind::UnitTest, DownloadBehavior::Error).with_scope_unit_test();
986 1 :
987 1 : const NUM_KEYS: u64 = 1000;
988 1 :
989 1 : let mut all_data: BTreeMap<u64, u64> = BTreeMap::new();
990 1 :
991 1001 : for idx in 0..NUM_KEYS {
992 1000 : let key_int: u64 = 1 + idx * 2;
993 1000 : let key = u64::to_be_bytes(key_int);
994 1000 : writer.append(&key, idx)?;
995 1 :
996 1000 : all_data.insert(key_int, idx);
997 1 : }
998 1 :
999 1 : let (root_offset, _writer) = writer.finish()?;
1000 1 :
1001 1 : let reader = DiskBtreeReader::new(0, root_offset, disk);
1002 1 :
1003 1 : reader.dump(&ctx).await?;
1004 1 :
1005 1 : use std::sync::Mutex;
1006 1 :
1007 1 : let result = Mutex::new(Vec::new());
1008 1 : let limit: AtomicUsize = AtomicUsize::new(10);
1009 41910 : let take_ten = |key: &[u8], value: u64| {
1010 41910 : let mut keybuf = [0u8; 8];
1011 41910 : keybuf.copy_from_slice(key);
1012 41910 : let key_int = u64::from_be_bytes(keybuf);
1013 41910 :
1014 41910 : let mut result = result.lock().unwrap();
1015 41910 : result.push((key_int, value));
1016 41910 :
1017 41910 : // keep going until we have 10 matches
1018 41910 : result.len() < limit.load(Ordering::Relaxed)
1019 41910 : };
1020 1 :
1021 2010 : for search_key_int in 0..(NUM_KEYS * 2 + 10) {
1022 2010 : let search_key = u64::to_be_bytes(search_key_int);
1023 2010 : assert_eq!(
1024 2010 : reader.get(&search_key, &ctx).await?,
1025 2010 : all_data.get(&search_key_int).cloned()
1026 1 : );
1027 1 :
1028 1 : // Test a forward scan starting with this key
1029 2010 : result.lock().unwrap().clear();
1030 2010 : reader
1031 2010 : .visit(&search_key, VisitDirection::Forwards, take_ten, &ctx)
1032 2010 : .await?;
1033 2010 : let expected = all_data
1034 2010 : .range(search_key_int..)
1035 2010 : .take(10)
1036 19910 : .map(|(&key, &val)| (key, val))
1037 2010 : .collect::<Vec<(u64, u64)>>();
1038 2010 : assert_eq!(*result.lock().unwrap(), expected);
1039 1 :
1040 1 : // And a backwards scan
1041 2010 : result.lock().unwrap().clear();
1042 2010 : reader
1043 2010 : .visit(&search_key, VisitDirection::Backwards, take_ten, &ctx)
1044 2010 : .await?;
1045 2010 : let expected = all_data
1046 2010 : .range(..=search_key_int)
1047 2010 : .rev()
1048 2010 : .take(10)
1049 20000 : .map(|(&key, &val)| (key, val))
1050 2010 : .collect::<Vec<(u64, u64)>>();
1051 2010 : assert_eq!(*result.lock().unwrap(), expected);
1052 1 : }
1053 1 :
1054 1 : // full scan
1055 1 : let search_key = u64::to_be_bytes(0);
1056 1 : limit.store(usize::MAX, Ordering::Relaxed);
1057 1 : result.lock().unwrap().clear();
1058 1 : reader
1059 1 : .visit(&search_key, VisitDirection::Forwards, take_ten, &ctx)
1060 1 : .await?;
1061 1 : let expected = all_data
1062 1 : .iter()
1063 1000 : .map(|(&key, &val)| (key, val))
1064 1 : .collect::<Vec<(u64, u64)>>();
1065 1 : assert_eq!(*result.lock().unwrap(), expected);
1066 1 :
1067 1 : // full scan
1068 1 : let search_key = u64::to_be_bytes(u64::MAX);
1069 1 : limit.store(usize::MAX, Ordering::Relaxed);
1070 1 : result.lock().unwrap().clear();
1071 1 : reader
1072 1 : .visit(&search_key, VisitDirection::Backwards, take_ten, &ctx)
1073 1 : .await?;
1074 1 : let expected = all_data
1075 1 : .iter()
1076 1 : .rev()
1077 1000 : .map(|(&key, &val)| (key, val))
1078 1 : .collect::<Vec<(u64, u64)>>();
1079 1 : assert_eq!(*result.lock().unwrap(), expected);
1080 1 :
1081 1 : Ok(())
1082 1 : }
1083 :
1084 : #[tokio::test]
1085 1 : async fn random_data() -> Result<()> {
1086 1 : let ctx = RequestContext::new(TaskKind::UnitTest, DownloadBehavior::Error);
1087 1 :
1088 1 : // Generate random keys with exponential distribution, to
1089 1 : // exercise the prefix compression
1090 1 : const NUM_KEYS: usize = 100000;
1091 1 : let mut all_data: BTreeMap<u128, u64> = BTreeMap::new();
1092 100001 : for idx in 0..NUM_KEYS {
1093 100000 : let u: f64 = rand::thread_rng().gen_range(0.0..1.0);
1094 100000 : let t = -(f64::ln(u));
1095 100000 : let key_int = (t * 1000000.0) as u128;
1096 100000 :
1097 100000 : all_data.insert(key_int, idx as u64);
1098 100000 : }
1099 1 :
1100 1 : // Build a tree from it
1101 1 : let mut disk = TestDisk::new();
1102 1 : let mut writer = DiskBtreeBuilder::<_, 16>::new(&mut disk);
1103 1 :
1104 97605 : for (&key, &val) in all_data.iter() {
1105 97605 : writer.append(&u128::to_be_bytes(key), val)?;
1106 1 : }
1107 1 : let (root_offset, _writer) = writer.finish()?;
1108 1 :
1109 1 : let reader = DiskBtreeReader::new(0, root_offset, disk);
1110 1 :
1111 1 : // Test get() operation on all the keys
1112 97605 : for (&key, &val) in all_data.iter() {
1113 97605 : let search_key = u128::to_be_bytes(key);
1114 97605 : assert_eq!(reader.get(&search_key, &ctx).await?, Some(val));
1115 1 : }
1116 1 :
1117 1 : // Test get() operations on random keys, most of which will not exist
1118 100001 : for _ in 0..100000 {
1119 100000 : let key_int = rand::thread_rng().r#gen::<u128>();
1120 100000 : let search_key = u128::to_be_bytes(key_int);
1121 100000 : assert!(reader.get(&search_key, &ctx).await? == all_data.get(&key_int).cloned());
1122 1 : }
1123 1 :
1124 1 : // Test boundary cases
1125 1 : assert!(
1126 1 : reader.get(&u128::to_be_bytes(u128::MIN), &ctx).await?
1127 1 : == all_data.get(&u128::MIN).cloned()
1128 1 : );
1129 1 : assert!(
1130 1 : reader.get(&u128::to_be_bytes(u128::MAX), &ctx).await?
1131 1 : == all_data.get(&u128::MAX).cloned()
1132 1 : );
1133 1 :
1134 1 : // Test iterator and get_stream API
1135 1 : let mut iter = reader.iter(&[0; 16], &ctx);
1136 1 : let mut cnt = 0;
1137 97606 : while let Some(res) = iter.next().await {
1138 97605 : let (key, val) = res?;
1139 97605 : let key = u128::from_be_bytes(key.as_slice().try_into().unwrap());
1140 97605 : assert_eq!(val, *all_data.get(&key).unwrap());
1141 97605 : cnt += 1;
1142 1 : }
1143 1 : assert_eq!(cnt, all_data.len());
1144 1 :
1145 1 : Ok(())
1146 1 : }
1147 :
1148 : #[test]
1149 1 : fn unsorted_input() {
1150 1 : let mut disk = TestDisk::new();
1151 1 : let mut writer = DiskBtreeBuilder::<_, 2>::new(&mut disk);
1152 1 :
1153 1 : let _ = writer.append(b"ba", 1);
1154 1 : let _ = writer.append(b"bb", 2);
1155 1 : let err = writer.append(b"aa", 3).expect_err("should've failed");
1156 1 : match err {
1157 1 : DiskBtreeError::UnsortedInput { key, last_key } => {
1158 1 : assert_eq!(key.as_ref(), b"aa".as_slice());
1159 1 : assert_eq!(last_key.as_ref(), b"bb".as_slice());
1160 : }
1161 0 : _ => panic!("unexpected error variant, expected DiskBtreeError::UnsortedInput"),
1162 : }
1163 1 : }
1164 :
1165 : ///
1166 : /// This test contains a particular data set, see disk_btree_test_data.rs
1167 : ///
1168 : #[tokio::test]
1169 1 : async fn particular_data() -> Result<()> {
1170 1 : // Build a tree from it
1171 1 : let mut disk = TestDisk::new();
1172 1 : let mut writer = DiskBtreeBuilder::<_, 26>::new(&mut disk);
1173 1 : let ctx =
1174 1 : RequestContext::new(TaskKind::UnitTest, DownloadBehavior::Error).with_scope_unit_test();
1175 1 :
1176 2001 : for (key, val) in disk_btree_test_data::TEST_DATA {
1177 2000 : writer.append(&key, val)?;
1178 1 : }
1179 1 : let (root_offset, writer) = writer.finish()?;
1180 1 :
1181 1 : println!("SIZE: {} blocks", writer.blocks.len());
1182 1 :
1183 1 : let reader = DiskBtreeReader::new(0, root_offset, disk);
1184 1 :
1185 1 : // Test get() operation on all the keys
1186 2001 : for (key, val) in disk_btree_test_data::TEST_DATA {
1187 2000 : assert_eq!(reader.get(&key, &ctx).await?, Some(val));
1188 1 : }
1189 1 :
1190 1 : // Test full scan
1191 1 : let mut count = 0;
1192 1 : reader
1193 1 : .visit(
1194 1 : &[0u8; 26],
1195 1 : VisitDirection::Forwards,
1196 2000 : |_key, _value| {
1197 2000 : count += 1;
1198 2000 : true
1199 2000 : },
1200 1 : &ctx,
1201 1 : )
1202 1 : .await?;
1203 1 : assert_eq!(count, disk_btree_test_data::TEST_DATA.len());
1204 1 :
1205 1 : reader.dump(&ctx).await?;
1206 1 :
1207 1 : Ok(())
1208 1 : }
1209 : }
1210 :
1211 : #[cfg(test)]
1212 : #[path = "disk_btree_test_data.rs"]
1213 : mod disk_btree_test_data;
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