Line data Source code
1 : //! See docs/rfcs/031-sharding-static.md for an overview of sharding.
2 : //!
3 : //! This module contains a variety of types used to represent the concept of sharding
4 : //! a Neon tenant across multiple physical shards. Since there are quite a few of these,
5 : //! we provide an summary here.
6 : //!
7 : //! Types used to describe shards:
8 : //! - [`ShardCount`] describes how many shards make up a tenant, plus the magic `unsharded` value
9 : //! which identifies a tenant which is not shard-aware. This means its storage paths do not include
10 : //! a shard suffix.
11 : //! - [`ShardNumber`] is simply the zero-based index of a shard within a tenant.
12 : //! - [`ShardIndex`] is the 2-tuple of `ShardCount` and `ShardNumber`, it's just like a `TenantShardId`
13 : //! without the tenant ID. This is useful for things that are implicitly scoped to a particular
14 : //! tenant, such as layer files.
15 : //! - [`ShardIdentity`]` is the full description of a particular shard's parameters, in sufficient
16 : //! detail to convert a [`Key`] to a [`ShardNumber`] when deciding where to write/read.
17 : //! - The [`ShardSlug`] is a terse formatter for ShardCount and ShardNumber, written as
18 : //! four hex digits. An unsharded tenant is `0000`.
19 : //! - [`TenantShardId`] is the unique ID of a particular shard within a particular tenant
20 : //!
21 : //! Types used to describe the parameters for data distribution in a sharded tenant:
22 : //! - [`ShardStripeSize`] controls how long contiguous runs of [`Key`]s (stripes) are when distributed across
23 : //! multiple shards. Its value is given in 8kiB pages.
24 : //! - [`ShardLayout`] describes the data distribution scheme, and at time of writing is
25 : //! always zero: this is provided for future upgrades that might introduce different
26 : //! data distribution schemes.
27 : //!
28 : //! Examples:
29 : //! - A legacy unsharded tenant has one shard with ShardCount(0), ShardNumber(0), and its slug is 0000
30 : //! - A single sharded tenant has one shard with ShardCount(1), ShardNumber(0), and its slug is 0001
31 : //! - In a tenant with 4 shards, each shard has ShardCount(N), ShardNumber(i) where i in 0..N-1 (inclusive),
32 : //! and their slugs are 0004, 0104, 0204, and 0304.
33 :
34 : use std::hash::{Hash, Hasher};
35 :
36 : #[doc(inline)]
37 : pub use ::utils::shard::*;
38 : use postgres_ffi_types::forknum::INIT_FORKNUM;
39 : use serde::{Deserialize, Serialize};
40 : use utils::critical;
41 :
42 : use crate::key::Key;
43 : use crate::models::ShardParameters;
44 :
45 : /// The ShardIdentity contains enough information to map a [`Key`] to a [`ShardNumber`],
46 : /// and to check whether that [`ShardNumber`] is the same as the current shard.
47 0 : #[derive(Clone, Copy, Serialize, Deserialize, Eq, PartialEq, Debug)]
48 : pub struct ShardIdentity {
49 : pub number: ShardNumber,
50 : pub count: ShardCount,
51 : pub stripe_size: ShardStripeSize,
52 : layout: ShardLayout,
53 : }
54 :
55 : /// Hash implementation
56 : ///
57 : /// The stripe size cannot change dynamically, so it can be ignored for efficiency reasons.
58 : impl Hash for ShardIdentity {
59 148146 : fn hash<H: Hasher>(&self, state: &mut H) {
60 : let ShardIdentity {
61 148146 : number,
62 148146 : count,
63 : stripe_size: _,
64 : layout: _,
65 148146 : } = self;
66 :
67 148146 : number.0.hash(state);
68 148146 : count.0.hash(state);
69 0 : }
70 : }
71 :
72 : /// Layout version: for future upgrades where we might change how the key->shard mapping works
73 0 : #[derive(Clone, Copy, Serialize, Deserialize, Eq, PartialEq, Hash, Debug)]
74 : pub struct ShardLayout(u8);
75 :
76 : const LAYOUT_V1: ShardLayout = ShardLayout(1);
77 : /// ShardIdentity uses a magic layout value to indicate if it is unusable
78 : const LAYOUT_BROKEN: ShardLayout = ShardLayout(255);
79 :
80 : /// The default stripe size in pages. 16 MiB divided by 8 kiB page size.
81 : ///
82 : /// A lower stripe size distributes ingest load better across shards, but reduces IO amortization.
83 : /// 16 MiB appears to be a reasonable balance: <https://github.com/neondatabase/neon/pull/10510>.
84 : pub const DEFAULT_STRIPE_SIZE: ShardStripeSize = ShardStripeSize(16 * 1024 / 8);
85 :
86 : #[derive(thiserror::Error, Debug, PartialEq, Eq)]
87 : pub enum ShardConfigError {
88 : #[error("Invalid shard count")]
89 : InvalidCount,
90 : #[error("Invalid shard number")]
91 : InvalidNumber,
92 : #[error("Invalid stripe size")]
93 : InvalidStripeSize,
94 : }
95 :
96 : impl ShardIdentity {
97 : /// An identity with number=0 count=0 is a "none" identity, which represents legacy
98 : /// tenants. Modern single-shard tenants should not use this: they should
99 : /// have number=0 count=1.
100 646 : pub const fn unsharded() -> Self {
101 646 : Self {
102 646 : number: ShardNumber(0),
103 646 : count: ShardCount(0),
104 646 : layout: LAYOUT_V1,
105 646 : stripe_size: DEFAULT_STRIPE_SIZE,
106 646 : }
107 646 : }
108 :
109 : /// An unsharded identity with the given stripe size (if non-zero). This is typically used to
110 : /// carry over a stripe size for an unsharded tenant from persistent storage.
111 0 : pub fn unsharded_with_stripe_size(stripe_size: ShardStripeSize) -> Self {
112 0 : let mut shard_identity = Self::unsharded();
113 0 : if stripe_size.0 > 0 {
114 0 : shard_identity.stripe_size = stripe_size;
115 0 : }
116 0 : shard_identity
117 0 : }
118 :
119 : /// A broken instance of this type is only used for `TenantState::Broken` tenants,
120 : /// which are constructed in code paths that don't have access to proper configuration.
121 : ///
122 : /// A ShardIdentity in this state may not be used for anything, and should not be persisted.
123 : /// Enforcement is via assertions, to avoid making our interface fallible for this
124 : /// edge case: it is the Tenant's responsibility to avoid trying to do any I/O when in a broken
125 : /// state, and by extension to avoid trying to do any page->shard resolution.
126 0 : pub fn broken(number: ShardNumber, count: ShardCount) -> Self {
127 0 : Self {
128 0 : number,
129 0 : count,
130 0 : layout: LAYOUT_BROKEN,
131 0 : stripe_size: DEFAULT_STRIPE_SIZE,
132 0 : }
133 0 : }
134 :
135 : /// The "unsharded" value is distinct from simply having a single shard: it represents
136 : /// a tenant which is not shard-aware at all, and whose storage paths will not include
137 : /// a shard suffix.
138 191 : pub fn is_unsharded(&self) -> bool {
139 191 : self.number == ShardNumber(0) && self.count == ShardCount(0)
140 191 : }
141 :
142 : /// Count must be nonzero, and number must be < count. To construct
143 : /// the legacy case (count==0), use Self::unsharded instead.
144 13358 : pub fn new(
145 13358 : number: ShardNumber,
146 13358 : count: ShardCount,
147 13358 : stripe_size: ShardStripeSize,
148 13358 : ) -> Result<Self, ShardConfigError> {
149 13358 : if count.0 == 0 {
150 1 : Err(ShardConfigError::InvalidCount)
151 13357 : } else if number.0 > count.0 - 1 {
152 3 : Err(ShardConfigError::InvalidNumber)
153 13354 : } else if stripe_size.0 == 0 {
154 1 : Err(ShardConfigError::InvalidStripeSize)
155 : } else {
156 13353 : Ok(Self {
157 13353 : number,
158 13353 : count,
159 13353 : layout: LAYOUT_V1,
160 13353 : stripe_size,
161 13353 : })
162 : }
163 13358 : }
164 :
165 : /// For use when creating ShardIdentity instances for new shards, where a creation request
166 : /// specifies the ShardParameters that apply to all shards.
167 122 : pub fn from_params(number: ShardNumber, params: ShardParameters) -> Self {
168 122 : Self {
169 122 : number,
170 122 : count: params.count,
171 122 : layout: LAYOUT_V1,
172 122 : stripe_size: params.stripe_size,
173 122 : }
174 122 : }
175 :
176 : /// Asserts that the given shard identities are equal. Changes to shard parameters will likely
177 : /// result in data corruption.
178 0 : pub fn assert_equal(&self, other: ShardIdentity) {
179 0 : if self != &other {
180 : // TODO: for now, we're conservative and just log errors in production. Turn this into a
181 : // real assertion when we're confident it doesn't misfire, and also reject requests that
182 : // attempt to change it with an error response.
183 0 : critical!("shard identity mismatch: {self:?} != {other:?}");
184 0 : }
185 0 : }
186 :
187 2731458 : fn is_broken(&self) -> bool {
188 2731458 : self.layout == LAYOUT_BROKEN
189 2731458 : }
190 :
191 1542 : pub fn get_shard_number(&self, key: &Key) -> ShardNumber {
192 1542 : assert!(!self.is_broken());
193 1542 : key_to_shard_number(self.count, self.stripe_size, key)
194 1542 : }
195 :
196 : /// Return true if the key is stored only on this shard. This does not include
197 : /// global keys, see is_key_global().
198 : ///
199 : /// Shards must ingest _at least_ keys which return true from this check.
200 2729916 : pub fn is_key_local(&self, key: &Key) -> bool {
201 2729916 : assert!(!self.is_broken());
202 2729916 : if self.count < ShardCount(2) || (key_is_shard0(key) && self.number == ShardNumber(0)) {
203 2693817 : true
204 : } else {
205 36099 : key_to_shard_number(self.count, self.stripe_size, key) == self.number
206 : }
207 2729916 : }
208 :
209 : /// Return true if the key should be stored on all shards, not just one.
210 36192 : pub fn is_key_global(&self, key: &Key) -> bool {
211 36192 : if key.is_slru_block_key()
212 36192 : || key.is_slru_segment_size_key()
213 36192 : || key.is_aux_file_key()
214 36192 : || key.is_slru_dir_key()
215 : {
216 : // Special keys that are only stored on shard 0
217 24 : false
218 36168 : } else if key.is_rel_block_key() {
219 : // Ordinary relation blocks are distributed across shards
220 36086 : false
221 82 : } else if key.is_rel_size_key() {
222 : // All shards maintain rel size keys (although only shard 0 is responsible for
223 : // keeping it strictly accurate, other shards just reflect the highest block they've ingested)
224 5 : true
225 : } else {
226 : // For everything else, we assume it must be kept everywhere, because ingest code
227 : // might assume this -- this covers functionality where the ingest code has
228 : // not (yet) been made fully shard aware.
229 77 : true
230 : }
231 36192 : }
232 :
233 : /// Return true if the key should be discarded if found in this shard's
234 : /// data store, e.g. during compaction after a split.
235 : ///
236 : /// Shards _may_ drop keys which return false here, but are not obliged to.
237 1414890 : pub fn is_key_disposable(&self, key: &Key) -> bool {
238 1414890 : if self.count < ShardCount(2) {
239 : // Fast path: unsharded tenant doesn't dispose of anything
240 1378710 : return false;
241 36180 : }
242 :
243 36180 : if self.is_key_global(key) {
244 70 : false
245 : } else {
246 36110 : !self.is_key_local(key)
247 : }
248 1414890 : }
249 :
250 : /// Obtains the shard number and count combined into a `ShardIndex`.
251 189 : pub fn shard_index(&self) -> ShardIndex {
252 189 : ShardIndex {
253 189 : shard_count: self.count,
254 189 : shard_number: self.number,
255 189 : }
256 189 : }
257 :
258 4 : pub fn shard_slug(&self) -> String {
259 4 : if self.count > ShardCount(0) {
260 4 : format!("-{:02x}{:02x}", self.number.0, self.count.0)
261 : } else {
262 0 : String::new()
263 : }
264 4 : }
265 :
266 : /// Convenience for checking if this identity is the 0th shard in a tenant,
267 : /// for special cases on shard 0 such as ingesting relation sizes.
268 1487 : pub fn is_shard_zero(&self) -> bool {
269 1487 : self.number == ShardNumber(0)
270 1487 : }
271 : }
272 :
273 : /// Whether this key is always held on shard 0 (e.g. shard 0 holds all SLRU keys
274 : /// in order to be able to serve basebackup requests without peer communication).
275 72248 : fn key_is_shard0(key: &Key) -> bool {
276 : // To decide what to shard out to shards >0, we apply a simple rule that only
277 : // relation pages are distributed to shards other than shard zero. Everything else gets
278 : // stored on shard 0. This guarantees that shard 0 can independently serve basebackup
279 : // requests, and any request other than those for particular blocks in relations.
280 : //
281 : // The only exception to this rule is "initfork" data -- this relates to postgres's UNLOGGED table
282 : // type. These are special relations, usually with only 0 or 1 blocks, and we store them on shard 0
283 : // because they must be included in basebackups.
284 72248 : let is_initfork = key.field5 == INIT_FORKNUM;
285 :
286 72248 : !key.is_rel_block_key() || is_initfork
287 72248 : }
288 :
289 : /// Provide the same result as the function in postgres `hashfn.h` with the same name
290 72195 : fn murmurhash32(mut h: u32) -> u32 {
291 72195 : h ^= h >> 16;
292 72195 : h = h.wrapping_mul(0x85ebca6b);
293 72195 : h ^= h >> 13;
294 72195 : h = h.wrapping_mul(0xc2b2ae35);
295 72195 : h ^= h >> 16;
296 72195 : h
297 72195 : }
298 :
299 : /// Provide the same result as the function in postgres `hashfn.h` with the same name
300 36098 : fn hash_combine(mut a: u32, mut b: u32) -> u32 {
301 36098 : b = b.wrapping_add(0x9e3779b9);
302 36098 : b = b.wrapping_add(a << 6);
303 36098 : b = b.wrapping_add(a >> 2);
304 :
305 36098 : a ^= b;
306 36098 : a
307 36098 : }
308 :
309 : /// Where a Key is to be distributed across shards, select the shard. This function
310 : /// does not account for keys that should be broadcast across shards.
311 : ///
312 : /// The hashing in this function must exactly match what we do in postgres smgr
313 : /// code. The resulting distribution of pages is intended to preserve locality within
314 : /// `stripe_size` ranges of contiguous block numbers in the same relation, while otherwise
315 : /// distributing data pseudo-randomly.
316 : ///
317 : /// The mapping of key to shard is not stable across changes to ShardCount: this is intentional
318 : /// and will be handled at higher levels when shards are split.
319 37642 : pub fn key_to_shard_number(
320 37642 : count: ShardCount,
321 37642 : stripe_size: ShardStripeSize,
322 37642 : key: &Key,
323 37642 : ) -> ShardNumber {
324 : // Fast path for un-sharded tenants or broadcast keys
325 37642 : if count < ShardCount(2) || key_is_shard0(key) {
326 1545 : return ShardNumber(0);
327 36097 : }
328 :
329 : // relNode
330 36097 : let mut hash = murmurhash32(key.field4);
331 : // blockNum/stripe size
332 36097 : hash = hash_combine(hash, murmurhash32(key.field6 / stripe_size.0));
333 :
334 36097 : ShardNumber((hash % count.0 as u32) as u8)
335 37642 : }
336 :
337 : /// For debugging, while not exposing the internals.
338 : #[derive(Debug)]
339 : #[allow(unused)] // used by debug formatting by pagectl
340 : struct KeyShardingInfo {
341 : shard0: bool,
342 : shard_number: ShardNumber,
343 : }
344 :
345 0 : pub fn describe(
346 0 : key: &Key,
347 0 : shard_count: ShardCount,
348 0 : stripe_size: ShardStripeSize,
349 0 : ) -> impl std::fmt::Debug {
350 0 : KeyShardingInfo {
351 0 : shard0: key_is_shard0(key),
352 0 : shard_number: key_to_shard_number(shard_count, stripe_size, key),
353 0 : }
354 0 : }
355 :
356 : #[cfg(test)]
357 : mod tests {
358 : use std::str::FromStr;
359 :
360 : use utils::Hex;
361 : use utils::id::TenantId;
362 :
363 : use super::*;
364 :
365 : const EXAMPLE_TENANT_ID: &str = "1f359dd625e519a1a4e8d7509690f6fc";
366 :
367 : #[test]
368 1 : fn tenant_shard_id_string() -> Result<(), hex::FromHexError> {
369 1 : let example = TenantShardId {
370 1 : tenant_id: TenantId::from_str(EXAMPLE_TENANT_ID).unwrap(),
371 1 : shard_count: ShardCount(10),
372 1 : shard_number: ShardNumber(7),
373 1 : };
374 :
375 1 : let encoded = format!("{example}");
376 :
377 1 : let expected = format!("{EXAMPLE_TENANT_ID}-070a");
378 1 : assert_eq!(&encoded, &expected);
379 :
380 1 : let decoded = TenantShardId::from_str(&encoded)?;
381 :
382 1 : assert_eq!(example, decoded);
383 :
384 1 : Ok(())
385 1 : }
386 :
387 : #[test]
388 1 : fn tenant_shard_id_binary() -> Result<(), hex::FromHexError> {
389 1 : let example = TenantShardId {
390 1 : tenant_id: TenantId::from_str(EXAMPLE_TENANT_ID).unwrap(),
391 1 : shard_count: ShardCount(10),
392 1 : shard_number: ShardNumber(7),
393 1 : };
394 :
395 1 : let encoded = bincode::serialize(&example).unwrap();
396 1 : let expected: [u8; 18] = [
397 1 : 0x1f, 0x35, 0x9d, 0xd6, 0x25, 0xe5, 0x19, 0xa1, 0xa4, 0xe8, 0xd7, 0x50, 0x96, 0x90,
398 1 : 0xf6, 0xfc, 0x07, 0x0a,
399 1 : ];
400 1 : assert_eq!(Hex(&encoded), Hex(&expected));
401 :
402 1 : let decoded = bincode::deserialize(&encoded).unwrap();
403 :
404 1 : assert_eq!(example, decoded);
405 :
406 1 : Ok(())
407 1 : }
408 :
409 : #[test]
410 1 : fn tenant_shard_id_backward_compat() -> Result<(), hex::FromHexError> {
411 : // Test that TenantShardId can decode a TenantId in human
412 : // readable form
413 1 : let example = TenantId::from_str(EXAMPLE_TENANT_ID).unwrap();
414 1 : let encoded = format!("{example}");
415 :
416 1 : assert_eq!(&encoded, EXAMPLE_TENANT_ID);
417 :
418 1 : let decoded = TenantShardId::from_str(&encoded)?;
419 :
420 1 : assert_eq!(example, decoded.tenant_id);
421 1 : assert_eq!(decoded.shard_count, ShardCount(0));
422 1 : assert_eq!(decoded.shard_number, ShardNumber(0));
423 :
424 1 : Ok(())
425 1 : }
426 :
427 : #[test]
428 1 : fn tenant_shard_id_forward_compat() -> Result<(), hex::FromHexError> {
429 : // Test that a legacy TenantShardId encodes into a form that
430 : // can be decoded as TenantId
431 1 : let example_tenant_id = TenantId::from_str(EXAMPLE_TENANT_ID).unwrap();
432 1 : let example = TenantShardId::unsharded(example_tenant_id);
433 1 : let encoded = format!("{example}");
434 :
435 1 : assert_eq!(&encoded, EXAMPLE_TENANT_ID);
436 :
437 1 : let decoded = TenantId::from_str(&encoded)?;
438 :
439 1 : assert_eq!(example_tenant_id, decoded);
440 :
441 1 : Ok(())
442 1 : }
443 :
444 : #[test]
445 1 : fn tenant_shard_id_legacy_binary() -> Result<(), hex::FromHexError> {
446 : // Unlike in human readable encoding, binary encoding does not
447 : // do any special handling of legacy unsharded TenantIds: this test
448 : // is equivalent to the main test for binary encoding, just verifying
449 : // that the same behavior applies when we have used `unsharded()` to
450 : // construct a TenantShardId.
451 1 : let example = TenantShardId::unsharded(TenantId::from_str(EXAMPLE_TENANT_ID).unwrap());
452 1 : let encoded = bincode::serialize(&example).unwrap();
453 :
454 1 : let expected: [u8; 18] = [
455 1 : 0x1f, 0x35, 0x9d, 0xd6, 0x25, 0xe5, 0x19, 0xa1, 0xa4, 0xe8, 0xd7, 0x50, 0x96, 0x90,
456 1 : 0xf6, 0xfc, 0x00, 0x00,
457 1 : ];
458 1 : assert_eq!(Hex(&encoded), Hex(&expected));
459 :
460 1 : let decoded = bincode::deserialize::<TenantShardId>(&encoded).unwrap();
461 1 : assert_eq!(example, decoded);
462 :
463 1 : Ok(())
464 1 : }
465 :
466 : #[test]
467 1 : fn shard_identity_validation() -> Result<(), ShardConfigError> {
468 : // Happy cases
469 1 : ShardIdentity::new(ShardNumber(0), ShardCount(1), DEFAULT_STRIPE_SIZE)?;
470 1 : ShardIdentity::new(ShardNumber(0), ShardCount(1), ShardStripeSize(1))?;
471 1 : ShardIdentity::new(ShardNumber(254), ShardCount(255), ShardStripeSize(1))?;
472 :
473 1 : assert_eq!(
474 1 : ShardIdentity::new(ShardNumber(0), ShardCount(0), DEFAULT_STRIPE_SIZE),
475 : Err(ShardConfigError::InvalidCount)
476 : );
477 1 : assert_eq!(
478 1 : ShardIdentity::new(ShardNumber(10), ShardCount(10), DEFAULT_STRIPE_SIZE),
479 : Err(ShardConfigError::InvalidNumber)
480 : );
481 1 : assert_eq!(
482 1 : ShardIdentity::new(ShardNumber(11), ShardCount(10), DEFAULT_STRIPE_SIZE),
483 : Err(ShardConfigError::InvalidNumber)
484 : );
485 1 : assert_eq!(
486 1 : ShardIdentity::new(ShardNumber(255), ShardCount(255), DEFAULT_STRIPE_SIZE),
487 : Err(ShardConfigError::InvalidNumber)
488 : );
489 1 : assert_eq!(
490 1 : ShardIdentity::new(ShardNumber(0), ShardCount(1), ShardStripeSize(0)),
491 : Err(ShardConfigError::InvalidStripeSize)
492 : );
493 :
494 1 : Ok(())
495 1 : }
496 :
497 : #[test]
498 1 : fn shard_index_human_encoding() -> Result<(), hex::FromHexError> {
499 1 : let example = ShardIndex {
500 1 : shard_number: ShardNumber(13),
501 1 : shard_count: ShardCount(17),
502 1 : };
503 1 : let expected: String = "0d11".to_string();
504 1 : let encoded = format!("{example}");
505 1 : assert_eq!(&encoded, &expected);
506 :
507 1 : let decoded = ShardIndex::from_str(&encoded)?;
508 1 : assert_eq!(example, decoded);
509 1 : Ok(())
510 1 : }
511 :
512 : #[test]
513 1 : fn shard_index_binary_encoding() -> Result<(), hex::FromHexError> {
514 1 : let example = ShardIndex {
515 1 : shard_number: ShardNumber(13),
516 1 : shard_count: ShardCount(17),
517 1 : };
518 1 : let expected: [u8; 2] = [0x0d, 0x11];
519 :
520 1 : let encoded = bincode::serialize(&example).unwrap();
521 1 : assert_eq!(Hex(&encoded), Hex(&expected));
522 1 : let decoded = bincode::deserialize(&encoded).unwrap();
523 1 : assert_eq!(example, decoded);
524 :
525 1 : Ok(())
526 1 : }
527 :
528 : // These are only smoke tests to spot check that our implementation doesn't
529 : // deviate from a few examples values: not aiming to validate the overall
530 : // hashing algorithm.
531 : #[test]
532 1 : fn murmur_hash() {
533 1 : assert_eq!(murmurhash32(0), 0);
534 :
535 1 : assert_eq!(hash_combine(0xb1ff3b40, 0), 0xfb7923c9);
536 1 : }
537 :
538 : #[test]
539 1 : fn shard_mapping() {
540 1 : let key = Key {
541 1 : field1: 0x00,
542 1 : field2: 0x67f,
543 1 : field3: 0x5,
544 1 : field4: 0x400c,
545 1 : field5: 0x00,
546 1 : field6: 0x7d06,
547 1 : };
548 :
549 1 : let shard = key_to_shard_number(ShardCount(10), ShardStripeSize(32768), &key);
550 1 : assert_eq!(shard, ShardNumber(8));
551 1 : }
552 :
553 : #[test]
554 1 : fn shard_id_split() {
555 1 : let tenant_id = TenantId::generate();
556 1 : let parent = TenantShardId::unsharded(tenant_id);
557 :
558 : // Unsharded into 2
559 1 : assert_eq!(
560 1 : parent.split(ShardCount(2)),
561 1 : vec![
562 1 : TenantShardId {
563 1 : tenant_id,
564 1 : shard_count: ShardCount(2),
565 1 : shard_number: ShardNumber(0)
566 1 : },
567 1 : TenantShardId {
568 1 : tenant_id,
569 1 : shard_count: ShardCount(2),
570 1 : shard_number: ShardNumber(1)
571 1 : }
572 : ]
573 : );
574 :
575 : // Unsharded into 4
576 1 : assert_eq!(
577 1 : parent.split(ShardCount(4)),
578 1 : vec![
579 1 : TenantShardId {
580 1 : tenant_id,
581 1 : shard_count: ShardCount(4),
582 1 : shard_number: ShardNumber(0)
583 1 : },
584 1 : TenantShardId {
585 1 : tenant_id,
586 1 : shard_count: ShardCount(4),
587 1 : shard_number: ShardNumber(1)
588 1 : },
589 1 : TenantShardId {
590 1 : tenant_id,
591 1 : shard_count: ShardCount(4),
592 1 : shard_number: ShardNumber(2)
593 1 : },
594 1 : TenantShardId {
595 1 : tenant_id,
596 1 : shard_count: ShardCount(4),
597 1 : shard_number: ShardNumber(3)
598 1 : }
599 : ]
600 : );
601 :
602 : // count=1 into 2 (check this works the same as unsharded.)
603 1 : let parent = TenantShardId {
604 1 : tenant_id,
605 1 : shard_count: ShardCount(1),
606 1 : shard_number: ShardNumber(0),
607 1 : };
608 1 : assert_eq!(
609 1 : parent.split(ShardCount(2)),
610 1 : vec![
611 1 : TenantShardId {
612 1 : tenant_id,
613 1 : shard_count: ShardCount(2),
614 1 : shard_number: ShardNumber(0)
615 1 : },
616 1 : TenantShardId {
617 1 : tenant_id,
618 1 : shard_count: ShardCount(2),
619 1 : shard_number: ShardNumber(1)
620 1 : }
621 : ]
622 : );
623 :
624 : // count=2 into count=8
625 1 : let parent = TenantShardId {
626 1 : tenant_id,
627 1 : shard_count: ShardCount(2),
628 1 : shard_number: ShardNumber(1),
629 1 : };
630 1 : assert_eq!(
631 1 : parent.split(ShardCount(8)),
632 1 : vec![
633 1 : TenantShardId {
634 1 : tenant_id,
635 1 : shard_count: ShardCount(8),
636 1 : shard_number: ShardNumber(1)
637 1 : },
638 1 : TenantShardId {
639 1 : tenant_id,
640 1 : shard_count: ShardCount(8),
641 1 : shard_number: ShardNumber(3)
642 1 : },
643 1 : TenantShardId {
644 1 : tenant_id,
645 1 : shard_count: ShardCount(8),
646 1 : shard_number: ShardNumber(5)
647 1 : },
648 1 : TenantShardId {
649 1 : tenant_id,
650 1 : shard_count: ShardCount(8),
651 1 : shard_number: ShardNumber(7)
652 1 : },
653 : ]
654 : );
655 1 : }
656 : }
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