Line data Source code
1 : // Copyright 2011 The LevelDB-Go and Pebble Authors. All rights reserved. Use
2 : // of this source code is governed by a BSD-style license that can be found in
3 : // the LICENSE file.
4 :
5 : package pebble
6 :
7 : import (
8 : "bytes"
9 : "context"
10 : "io"
11 : "sync"
12 : "unsafe"
13 :
14 : "github.com/cockroachdb/errors"
15 : "github.com/cockroachdb/pebble/internal/base"
16 : "github.com/cockroachdb/pebble/internal/bytealloc"
17 : "github.com/cockroachdb/pebble/internal/fastrand"
18 : "github.com/cockroachdb/pebble/internal/humanize"
19 : "github.com/cockroachdb/pebble/internal/invariants"
20 : "github.com/cockroachdb/pebble/internal/keyspan"
21 : "github.com/cockroachdb/pebble/internal/manifest"
22 : "github.com/cockroachdb/pebble/internal/rangekey"
23 : "github.com/cockroachdb/pebble/sstable"
24 : "github.com/cockroachdb/redact"
25 : )
26 :
27 : // iterPos describes the state of the internal iterator, in terms of whether it
28 : // is at the position returned to the user (cur), one ahead of the position
29 : // returned (next for forward iteration and prev for reverse iteration). The cur
30 : // position is split into two states, for forward and reverse iteration, since
31 : // we need to differentiate for switching directions.
32 : //
33 : // There is subtlety in what is considered the current position of the Iterator.
34 : // The internal iterator exposes a sequence of internal keys. There is not
35 : // always a single internalIterator position corresponding to the position
36 : // returned to the user. Consider the example:
37 : //
38 : // a.MERGE.9 a.MERGE.8 a.MERGE.7 a.SET.6 b.DELETE.9 b.DELETE.5 b.SET.4
39 : // \ /
40 : // \ Iterator.Key() = 'a' /
41 : //
42 : // The Iterator exposes one valid position at user key 'a' and the two exhausted
43 : // positions at the beginning and end of iteration. The underlying
44 : // internalIterator contains 7 valid positions and 2 exhausted positions.
45 : //
46 : // Iterator positioning methods must set iterPos to iterPosCur{Foward,Backward}
47 : // iff the user key at the current internalIterator position equals the
48 : // Iterator.Key returned to the user. This guarantees that a call to nextUserKey
49 : // or prevUserKey will advance to the next or previous iterator position.
50 : // iterPosCur{Forward,Backward} does not make any guarantee about the internal
51 : // iterator position among internal keys with matching user keys, and it will
52 : // vary subtly depending on the particular key kinds encountered. In the above
53 : // example, the iterator returning 'a' may set iterPosCurForward if the internal
54 : // iterator is positioned at any of a.MERGE.9, a.MERGE.8, a.MERGE.7 or a.SET.6.
55 : //
56 : // When setting iterPos to iterPosNext or iterPosPrev, the internal iterator
57 : // must be advanced to the first internalIterator position at a user key greater
58 : // (iterPosNext) or less (iterPosPrev) than the key returned to the user. An
59 : // internalIterator position that's !Valid() must also be considered greater or
60 : // less—depending on the direction of iteration—than the last valid Iterator
61 : // position.
62 : type iterPos int8
63 :
64 : const (
65 : iterPosCurForward iterPos = 0
66 : iterPosNext iterPos = 1
67 : iterPosPrev iterPos = -1
68 : iterPosCurReverse iterPos = -2
69 :
70 : // For limited iteration. When the iterator is at iterPosCurForwardPaused
71 : // - Next*() call should behave as if the internal iterator is already
72 : // at next (akin to iterPosNext).
73 : // - Prev*() call should behave as if the internal iterator is at the
74 : // current key (akin to iterPosCurForward).
75 : //
76 : // Similar semantics apply to CurReversePaused.
77 : iterPosCurForwardPaused iterPos = 2
78 : iterPosCurReversePaused iterPos = -3
79 : )
80 :
81 : // Approximate gap in bytes between samples of data read during iteration.
82 : // This is multiplied with a default ReadSamplingMultiplier of 1 << 4 to yield
83 : // 1 << 20 (1MB). The 1MB factor comes from:
84 : // https://github.com/cockroachdb/pebble/issues/29#issuecomment-494477985
85 : const readBytesPeriod uint64 = 1 << 16
86 :
87 : var errReversePrefixIteration = errors.New("pebble: unsupported reverse prefix iteration")
88 :
89 : // IteratorMetrics holds per-iterator metrics. These do not change over the
90 : // lifetime of the iterator.
91 : type IteratorMetrics struct {
92 : // The read amplification experienced by this iterator. This is the sum of
93 : // the memtables, the L0 sublevels and the non-empty Ln levels. Higher read
94 : // amplification generally results in slower reads, though allowing higher
95 : // read amplification can also result in faster writes.
96 : ReadAmp int
97 : }
98 :
99 : // IteratorStatsKind describes the two kind of iterator stats.
100 : type IteratorStatsKind int8
101 :
102 : const (
103 : // InterfaceCall represents calls to Iterator.
104 : InterfaceCall IteratorStatsKind = iota
105 : // InternalIterCall represents calls by Iterator to its internalIterator.
106 : InternalIterCall
107 : // NumStatsKind is the number of kinds, and is used for array sizing.
108 : NumStatsKind
109 : )
110 :
111 : // IteratorStats contains iteration stats.
112 : type IteratorStats struct {
113 : // ForwardSeekCount includes SeekGE, SeekPrefixGE, First.
114 : ForwardSeekCount [NumStatsKind]int
115 : // ReverseSeek includes SeekLT, Last.
116 : ReverseSeekCount [NumStatsKind]int
117 : // ForwardStepCount includes Next.
118 : ForwardStepCount [NumStatsKind]int
119 : // ReverseStepCount includes Prev.
120 : ReverseStepCount [NumStatsKind]int
121 : InternalStats InternalIteratorStats
122 : RangeKeyStats RangeKeyIteratorStats
123 : }
124 :
125 : var _ redact.SafeFormatter = &IteratorStats{}
126 :
127 : // InternalIteratorStats contains miscellaneous stats produced by internal
128 : // iterators.
129 : type InternalIteratorStats = base.InternalIteratorStats
130 :
131 : // RangeKeyIteratorStats contains miscellaneous stats about range keys
132 : // encountered by the iterator.
133 : type RangeKeyIteratorStats struct {
134 : // Count records the number of range keys encountered during
135 : // iteration. Range keys may be counted multiple times if the iterator
136 : // leaves a range key's bounds and then returns.
137 : Count int
138 : // ContainedPoints records the number of point keys encountered within the
139 : // bounds of a range key. Note that this includes point keys with suffixes
140 : // that sort both above and below the covering range key's suffix.
141 : ContainedPoints int
142 : // SkippedPoints records the count of the subset of ContainedPoints point
143 : // keys that were skipped during iteration due to range-key masking. It does
144 : // not include point keys that were never loaded because a
145 : // RangeKeyMasking.Filter excluded the entire containing block.
146 : SkippedPoints int
147 : }
148 :
149 : // Merge adds all of the argument's statistics to the receiver. It may be used
150 : // to accumulate stats across multiple iterators.
151 1 : func (s *RangeKeyIteratorStats) Merge(o RangeKeyIteratorStats) {
152 1 : s.Count += o.Count
153 1 : s.ContainedPoints += o.ContainedPoints
154 1 : s.SkippedPoints += o.SkippedPoints
155 1 : }
156 :
157 : // LazyValue is a lazy value. See the long comment in base.LazyValue.
158 : type LazyValue = base.LazyValue
159 :
160 : // Iterator iterates over a DB's key/value pairs in key order.
161 : //
162 : // An iterator must be closed after use, but it is not necessary to read an
163 : // iterator until exhaustion.
164 : //
165 : // An iterator is not goroutine-safe, but it is safe to use multiple iterators
166 : // concurrently, with each in a dedicated goroutine.
167 : //
168 : // It is also safe to use an iterator concurrently with modifying its
169 : // underlying DB, if that DB permits modification. However, the resultant
170 : // key/value pairs are not guaranteed to be a consistent snapshot of that DB
171 : // at a particular point in time.
172 : //
173 : // If an iterator encounters an error during any operation, it is stored by
174 : // the Iterator and surfaced through the Error method. All absolute
175 : // positioning methods (eg, SeekLT, SeekGT, First, Last, etc) reset any
176 : // accumulated error before positioning. All relative positioning methods (eg,
177 : // Next, Prev) return without advancing if the iterator has an accumulated
178 : // error.
179 : type Iterator struct {
180 : // The context is stored here since (a) Iterators are expected to be
181 : // short-lived (since they pin memtables and sstables), (b) plumbing a
182 : // context into every method is very painful, (c) they do not (yet) respect
183 : // context cancellation and are only used for tracing.
184 : ctx context.Context
185 : opts IterOptions
186 : merge Merge
187 : comparer base.Comparer
188 : iter internalIterator
189 : pointIter internalIterator
190 : // Either readState or version is set, but not both.
191 : readState *readState
192 : version *version
193 : // rangeKey holds iteration state specific to iteration over range keys.
194 : // The range key field may be nil if the Iterator has never been configured
195 : // to iterate over range keys. Its non-nilness cannot be used to determine
196 : // if the Iterator is currently iterating over range keys: For that, consult
197 : // the IterOptions using opts.rangeKeys(). If non-nil, its rangeKeyIter
198 : // field is guaranteed to be non-nil too.
199 : rangeKey *iteratorRangeKeyState
200 : // rangeKeyMasking holds state for range-key masking of point keys.
201 : rangeKeyMasking rangeKeyMasking
202 : err error
203 : // When iterValidityState=IterValid, key represents the current key, which
204 : // is backed by keyBuf.
205 : key []byte
206 : keyBuf []byte
207 : value LazyValue
208 : // For use in LazyValue.Clone.
209 : valueBuf []byte
210 : fetcher base.LazyFetcher
211 : // For use in LazyValue.Value.
212 : lazyValueBuf []byte
213 : valueCloser io.Closer
214 : // boundsBuf holds two buffers used to store the lower and upper bounds.
215 : // Whenever the Iterator's bounds change, the new bounds are copied into
216 : // boundsBuf[boundsBufIdx]. The two bounds share a slice to reduce
217 : // allocations. opts.LowerBound and opts.UpperBound point into this slice.
218 : boundsBuf [2][]byte
219 : boundsBufIdx int
220 : // iterKey, iterValue reflect the latest position of iter, except when
221 : // SetBounds is called. In that case, these are explicitly set to nil.
222 : iterKey *InternalKey
223 : iterValue LazyValue
224 : alloc *iterAlloc
225 : getIterAlloc *getIterAlloc
226 : prefixOrFullSeekKey []byte
227 : readSampling readSampling
228 : stats IteratorStats
229 : externalReaders [][]*sstable.Reader
230 :
231 : // Following fields used when constructing an iterator stack, eg, in Clone
232 : // and SetOptions or when re-fragmenting a batch's range keys/range dels.
233 : // Non-nil if this Iterator includes a Batch.
234 : batch *Batch
235 : newIters tableNewIters
236 : newIterRangeKey keyspan.TableNewSpanIter
237 : lazyCombinedIter lazyCombinedIter
238 : seqNum uint64
239 : // batchSeqNum is used by Iterators over indexed batches to detect when the
240 : // underlying batch has been mutated. The batch beneath an indexed batch may
241 : // be mutated while the Iterator is open, but new keys are not surfaced
242 : // until the next call to SetOptions.
243 : batchSeqNum uint64
244 : // batch{PointIter,RangeDelIter,RangeKeyIter} are used when the Iterator is
245 : // configured to read through an indexed batch. If a batch is set, these
246 : // iterators will be included within the iterator stack regardless of
247 : // whether the batch currently contains any keys of their kind. These
248 : // pointers are used during a call to SetOptions to refresh the Iterator's
249 : // view of its indexed batch.
250 : batchPointIter batchIter
251 : batchRangeDelIter keyspan.Iter
252 : batchRangeKeyIter keyspan.Iter
253 : // merging is a pointer to this iterator's point merging iterator. It
254 : // appears here because key visibility is handled by the merging iterator.
255 : // During SetOptions on an iterator over an indexed batch, this field is
256 : // used to update the merging iterator's batch snapshot.
257 : merging *mergingIter
258 :
259 : // Keeping the bools here after all the 8 byte aligned fields shrinks the
260 : // sizeof this struct by 24 bytes.
261 :
262 : // INVARIANT:
263 : // iterValidityState==IterAtLimit <=>
264 : // pos==iterPosCurForwardPaused || pos==iterPosCurReversePaused
265 : iterValidityState IterValidityState
266 : // Set to true by SetBounds, SetOptions. Causes the Iterator to appear
267 : // exhausted externally, while preserving the correct iterValidityState for
268 : // the iterator's internal state. Preserving the correct internal validity
269 : // is used for SeekPrefixGE(..., trySeekUsingNext), and SeekGE/SeekLT
270 : // optimizations after "no-op" calls to SetBounds and SetOptions.
271 : requiresReposition bool
272 : // The position of iter. When this is iterPos{Prev,Next} the iter has been
273 : // moved past the current key-value, which can only happen if
274 : // iterValidityState=IterValid, i.e., there is something to return to the
275 : // client for the current position.
276 : pos iterPos
277 : // Relates to the prefixOrFullSeekKey field above.
278 : hasPrefix bool
279 : // Used for deriving the value of SeekPrefixGE(..., trySeekUsingNext),
280 : // and SeekGE/SeekLT optimizations
281 : lastPositioningOp lastPositioningOpKind
282 : // Used for determining when it's safe to perform SeekGE optimizations that
283 : // reuse the iterator state to avoid the cost of a full seek if the iterator
284 : // is already positioned in the correct place. If the iterator's view of its
285 : // indexed batch was just refreshed, some optimizations cannot be applied on
286 : // the first seek after the refresh:
287 : // - SeekGE has a no-op optimization that does not seek on the internal
288 : // iterator at all if the iterator is already in the correct place.
289 : // This optimization cannot be performed if the internal iterator was
290 : // last positioned when the iterator had a different view of an
291 : // underlying batch.
292 : // - Seek[Prefix]GE set flags.TrySeekUsingNext()=true when the seek key is
293 : // greater than the previous operation's seek key, under the expectation
294 : // that the various internal iterators can use their current position to
295 : // avoid a full expensive re-seek. This applies to the batchIter as well.
296 : // However, if the view of the batch was just refreshed, the batchIter's
297 : // position is not useful because it may already be beyond new keys less
298 : // than the seek key. To prevent the use of this optimization in
299 : // batchIter, Seek[Prefix]GE set flags.BatchJustRefreshed()=true if this
300 : // bit is enabled.
301 : batchJustRefreshed bool
302 : // Used for an optimization in external iterators to reduce the number of
303 : // merging levels.
304 : forwardOnly bool
305 : // batchOnlyIter is set to true for Batch.NewBatchOnlyIter.
306 : batchOnlyIter bool
307 : // closePointIterOnce is set to true if this point iter can only be Close()d
308 : // once, _and_ closing i.iter and then i.pointIter would close i.pointIter
309 : // twice. This is necessary to track if the point iter is an internal iterator
310 : // that could release its resources to a pool on Close(), making it harder for
311 : // that iterator to make its own closes idempotent.
312 : //
313 : // TODO(bilal): Update SetOptions to always close out point key iterators when
314 : // they won't be used, so that Close() doesn't need to default to closing
315 : // point iterators twice.
316 : closePointIterOnce bool
317 : // Used in some tests to disable the random disabling of seek optimizations.
318 : forceEnableSeekOpt bool
319 : // Set to true if NextPrefix is not currently permitted. Defaults to false
320 : // in case an iterator never had any bounds.
321 : nextPrefixNotPermittedByUpperBound bool
322 : }
323 :
324 : // cmp is a convenience shorthand for the i.comparer.Compare function.
325 1 : func (i *Iterator) cmp(a, b []byte) int {
326 1 : return i.comparer.Compare(a, b)
327 1 : }
328 :
329 : // split is a convenience shorthand for the i.comparer.Split function.
330 1 : func (i *Iterator) split(a []byte) int {
331 1 : return i.comparer.Split(a)
332 1 : }
333 :
334 : // equal is a convenience shorthand for the i.comparer.Equal function.
335 1 : func (i *Iterator) equal(a, b []byte) bool {
336 1 : return i.comparer.Equal(a, b)
337 1 : }
338 :
339 : // iteratorRangeKeyState holds an iterator's range key iteration state.
340 : type iteratorRangeKeyState struct {
341 : opts *IterOptions
342 : cmp base.Compare
343 : split base.Split
344 : // rangeKeyIter holds the range key iterator stack that iterates over the
345 : // merged spans across the entirety of the LSM.
346 : rangeKeyIter keyspan.FragmentIterator
347 : iiter keyspan.InterleavingIter
348 : // stale is set to true when the range key state recorded here (in start,
349 : // end and keys) may not be in sync with the current range key at the
350 : // interleaving iterator's current position.
351 : //
352 : // When the interelaving iterator passes over a new span, it invokes the
353 : // SpanChanged hook defined on the `rangeKeyMasking` type, which sets stale
354 : // to true if the span is non-nil.
355 : //
356 : // The parent iterator may not be positioned over the interleaving
357 : // iterator's current position (eg, i.iterPos = iterPos{Next,Prev}), so
358 : // {keys,start,end} are only updated to the new range key during a call to
359 : // Iterator.saveRangeKey.
360 : stale bool
361 : // updated is used to signal to the Iterator client whether the state of
362 : // range keys has changed since the previous iterator position through the
363 : // `RangeKeyChanged` method. It's set to true during an Iterator positioning
364 : // operation that changes the state of the current range key. Each Iterator
365 : // positioning operation sets it back to false before executing.
366 : //
367 : // TODO(jackson): The lifecycle of {stale,updated,prevPosHadRangeKey} is
368 : // intricate and confusing. Try to refactor to reduce complexity.
369 : updated bool
370 : // prevPosHadRangeKey records whether the previous Iterator position had a
371 : // range key (HasPointAndRage() = (_, true)). It's updated at the beginning
372 : // of each new Iterator positioning operation. It's required by saveRangeKey to
373 : // to set `updated` appropriately: Without this record of the previous iterator
374 : // state, it's ambiguous whether an iterator only temporarily stepped onto a
375 : // position without a range key.
376 : prevPosHadRangeKey bool
377 : // rangeKeyOnly is set to true if at the current iterator position there is
378 : // no point key, only a range key start boundary.
379 : rangeKeyOnly bool
380 : // hasRangeKey is true when the current iterator position has a covering
381 : // range key (eg, a range key with bounds [<lower>,<upper>) such that
382 : // <lower> ≤ Key() < <upper>).
383 : hasRangeKey bool
384 : // start and end are the [start, end) boundaries of the current range keys.
385 : start []byte
386 : end []byte
387 :
388 : rangeKeyBuffers
389 :
390 : // iterConfig holds fields that are used for the construction of the
391 : // iterator stack, but do not need to be directly accessed during iteration.
392 : // This struct is bundled within the iteratorRangeKeyState struct to reduce
393 : // allocations.
394 : iterConfig rangekey.UserIteratorConfig
395 : }
396 :
397 : type rangeKeyBuffers struct {
398 : // keys is sorted by Suffix ascending.
399 : keys []RangeKeyData
400 : // buf is used to save range-key data before moving the range-key iterator.
401 : // Start and end boundaries, suffixes and values are all copied into buf.
402 : buf bytealloc.A
403 : // internal holds buffers used by the range key internal iterators.
404 : internal rangekey.Buffers
405 : }
406 :
407 1 : func (b *rangeKeyBuffers) PrepareForReuse() {
408 1 : const maxKeysReuse = 100
409 1 : if len(b.keys) > maxKeysReuse {
410 0 : b.keys = nil
411 0 : }
412 : // Avoid caching the key buf if it is overly large. The constant is
413 : // fairly arbitrary.
414 1 : if cap(b.buf) >= maxKeyBufCacheSize {
415 0 : b.buf = nil
416 1 : } else {
417 1 : b.buf = b.buf[:0]
418 1 : }
419 1 : b.internal.PrepareForReuse()
420 : }
421 :
422 1 : func (i *iteratorRangeKeyState) init(cmp base.Compare, split base.Split, opts *IterOptions) {
423 1 : i.cmp = cmp
424 1 : i.split = split
425 1 : i.opts = opts
426 1 : }
427 :
428 : var iterRangeKeyStateAllocPool = sync.Pool{
429 1 : New: func() interface{} {
430 1 : return &iteratorRangeKeyState{}
431 1 : },
432 : }
433 :
434 : // isEphemeralPosition returns true iff the current iterator position is
435 : // ephemeral, and won't be visited during subsequent relative positioning
436 : // operations.
437 : //
438 : // The iterator position resulting from a SeekGE or SeekPrefixGE that lands on a
439 : // straddling range key without a coincident point key is such a position.
440 1 : func (i *Iterator) isEphemeralPosition() bool {
441 1 : return i.opts.rangeKeys() && i.rangeKey != nil && i.rangeKey.rangeKeyOnly &&
442 1 : !i.equal(i.rangeKey.start, i.key)
443 1 : }
444 :
445 : type lastPositioningOpKind int8
446 :
447 : const (
448 : unknownLastPositionOp lastPositioningOpKind = iota
449 : seekPrefixGELastPositioningOp
450 : seekGELastPositioningOp
451 : seekLTLastPositioningOp
452 : // internalNextOp is a special internal iterator positioning operation used
453 : // by CanDeterministicallySingleDelete. It exists for enforcing requirements
454 : // around calling CanDeterministicallySingleDelete at most once per external
455 : // iterator position.
456 : internalNextOp
457 : // invalidatedLastPositionOp is similar to unknownLastPositionOp and the
458 : // only reason to distinguish this is for the wider set of SeekGE
459 : // optimizations we permit for the external iterator Iterator.forwardOnly
460 : // case. Most code predicates should be doing equality comparisons with one
461 : // of the seek* enum values, so this duplication should not result in code
462 : // of the form:
463 : // if unknownLastPositionOp || invalidLastPositionOp
464 : invalidatedLastPositionOp
465 : )
466 :
467 : // Limited iteration mode. Not for use with prefix iteration.
468 : //
469 : // SeekGE, SeekLT, Prev, Next have WithLimit variants, that pause the iterator
470 : // at the limit in a best-effort manner. The client should behave correctly
471 : // even if the limits are ignored. These limits are not "deep", in that they
472 : // are not passed down to the underlying collection of internalIterators. This
473 : // is because the limits are transient, and apply only until the next
474 : // iteration call. They serve mainly as a way to bound the amount of work when
475 : // two (or more) Iterators are being coordinated at a higher level.
476 : //
477 : // In limited iteration mode:
478 : // - Avoid using Iterator.Valid if the last call was to a *WithLimit() method.
479 : // The return value from the *WithLimit() method provides a more precise
480 : // disposition.
481 : // - The limit is exclusive for forward and inclusive for reverse.
482 : //
483 : //
484 : // Limited iteration mode & range keys
485 : //
486 : // Limited iteration interacts with range-key iteration. When range key
487 : // iteration is enabled, range keys are interleaved at their start boundaries.
488 : // Limited iteration must ensure that if a range key exists within the limit,
489 : // the iterator visits the range key.
490 : //
491 : // During forward limited iteration, this is trivial: An overlapping range key
492 : // must have a start boundary less than the limit, and the range key's start
493 : // boundary will be interleaved and found to be within the limit.
494 : //
495 : // During reverse limited iteration, the tail of the range key may fall within
496 : // the limit. The range key must be surfaced even if the range key's start
497 : // boundary is less than the limit, and if there are no point keys between the
498 : // current iterator position and the limit. To provide this guarantee, reverse
499 : // limited iteration ignores the limit as long as there is a range key
500 : // overlapping the iteration position.
501 :
502 : // IterValidityState captures the state of the Iterator.
503 : type IterValidityState int8
504 :
505 : const (
506 : // IterExhausted represents an Iterator that is exhausted.
507 : IterExhausted IterValidityState = iota
508 : // IterValid represents an Iterator that is valid.
509 : IterValid
510 : // IterAtLimit represents an Iterator that has a non-exhausted
511 : // internalIterator, but has reached a limit without any key for the
512 : // caller.
513 : IterAtLimit
514 : )
515 :
516 : // readSampling stores variables used to sample a read to trigger a read
517 : // compaction
518 : type readSampling struct {
519 : bytesUntilReadSampling uint64
520 : initialSamplePassed bool
521 : pendingCompactions readCompactionQueue
522 : // forceReadSampling is used for testing purposes to force a read sample on every
523 : // call to Iterator.maybeSampleRead()
524 : forceReadSampling bool
525 : }
526 :
527 1 : func (i *Iterator) findNextEntry(limit []byte) {
528 1 : i.iterValidityState = IterExhausted
529 1 : i.pos = iterPosCurForward
530 1 : if i.opts.rangeKeys() && i.rangeKey != nil {
531 1 : i.rangeKey.rangeKeyOnly = false
532 1 : }
533 :
534 : // Close the closer for the current value if one was open.
535 1 : if i.closeValueCloser() != nil {
536 0 : return
537 0 : }
538 :
539 1 : for i.iterKey != nil {
540 1 : key := *i.iterKey
541 1 :
542 1 : if i.hasPrefix {
543 1 : if n := i.split(key.UserKey); !i.equal(i.prefixOrFullSeekKey, key.UserKey[:n]) {
544 1 : return
545 1 : }
546 : }
547 : // Compare with limit every time we start at a different user key.
548 : // Note that given the best-effort contract of limit, we could avoid a
549 : // comparison in the common case by doing this only after
550 : // i.nextUserKey is called for the deletes below. However that makes
551 : // the behavior non-deterministic (since the behavior will vary based
552 : // on what has been compacted), which makes it hard to test with the
553 : // metamorphic test. So we forego that performance optimization.
554 1 : if limit != nil && i.cmp(limit, i.iterKey.UserKey) <= 0 {
555 1 : i.iterValidityState = IterAtLimit
556 1 : i.pos = iterPosCurForwardPaused
557 1 : return
558 1 : }
559 :
560 : // If the user has configured a SkipPoint function, invoke it to see
561 : // whether we should skip over the current user key.
562 1 : if i.opts.SkipPoint != nil && key.Kind() != InternalKeyKindRangeKeySet && i.opts.SkipPoint(i.iterKey.UserKey) {
563 1 : // NB: We could call nextUserKey, but in some cases the SkipPoint
564 1 : // predicate function might be cheaper than nextUserKey's key copy
565 1 : // and key comparison. This should be the case for MVCC suffix
566 1 : // comparisons, for example. In the future, we could expand the
567 1 : // SkipPoint interface to give the implementor more control over
568 1 : // whether we skip over just the internal key, the user key, or even
569 1 : // the key prefix.
570 1 : i.stats.ForwardStepCount[InternalIterCall]++
571 1 : i.iterKey, i.iterValue = i.iter.Next()
572 1 : continue
573 : }
574 :
575 1 : switch key.Kind() {
576 1 : case InternalKeyKindRangeKeySet:
577 1 : // Save the current key.
578 1 : i.keyBuf = append(i.keyBuf[:0], key.UserKey...)
579 1 : i.key = i.keyBuf
580 1 : i.value = LazyValue{}
581 1 : // There may also be a live point key at this userkey that we have
582 1 : // not yet read. We need to find the next entry with this user key
583 1 : // to find it. Save the range key so we don't lose it when we Next
584 1 : // the underlying iterator.
585 1 : i.saveRangeKey()
586 1 : pointKeyExists := i.nextPointCurrentUserKey()
587 1 : if i.err != nil {
588 0 : i.iterValidityState = IterExhausted
589 0 : return
590 0 : }
591 1 : i.rangeKey.rangeKeyOnly = !pointKeyExists
592 1 : i.iterValidityState = IterValid
593 1 : return
594 :
595 1 : case InternalKeyKindDelete, InternalKeyKindSingleDelete, InternalKeyKindDeleteSized:
596 1 : // NB: treating InternalKeyKindSingleDelete as equivalent to DEL is not
597 1 : // only simpler, but is also necessary for correctness due to
598 1 : // InternalKeyKindSSTableInternalObsoleteBit.
599 1 : i.nextUserKey()
600 1 : continue
601 :
602 1 : case InternalKeyKindSet, InternalKeyKindSetWithDelete:
603 1 : i.keyBuf = append(i.keyBuf[:0], key.UserKey...)
604 1 : i.key = i.keyBuf
605 1 : i.value = i.iterValue
606 1 : i.iterValidityState = IterValid
607 1 : i.saveRangeKey()
608 1 : return
609 :
610 1 : case InternalKeyKindMerge:
611 1 : // Resolving the merge may advance us to the next point key, which
612 1 : // may be covered by a different set of range keys. Save the range
613 1 : // key state so we don't lose it.
614 1 : i.saveRangeKey()
615 1 : if i.mergeForward(key) {
616 1 : i.iterValidityState = IterValid
617 1 : return
618 1 : }
619 :
620 : // The merge didn't yield a valid key, either because the value
621 : // merger indicated it should be deleted, or because an error was
622 : // encountered.
623 1 : i.iterValidityState = IterExhausted
624 1 : if i.err != nil {
625 0 : return
626 0 : }
627 1 : if i.pos != iterPosNext {
628 0 : i.nextUserKey()
629 0 : }
630 1 : if i.closeValueCloser() != nil {
631 0 : return
632 0 : }
633 1 : i.pos = iterPosCurForward
634 :
635 0 : default:
636 0 : i.err = base.CorruptionErrorf("pebble: invalid internal key kind: %d", errors.Safe(key.Kind()))
637 0 : i.iterValidityState = IterExhausted
638 0 : return
639 : }
640 : }
641 : }
642 :
643 1 : func (i *Iterator) nextPointCurrentUserKey() bool {
644 1 : // If the user has configured a SkipPoint function and the current user key
645 1 : // would be skipped by it, there's no need to step forward looking for a
646 1 : // point key. If we were to find one, it should be skipped anyways.
647 1 : if i.opts.SkipPoint != nil && i.opts.SkipPoint(i.key) {
648 1 : return false
649 1 : }
650 :
651 1 : i.pos = iterPosCurForward
652 1 :
653 1 : i.iterKey, i.iterValue = i.iter.Next()
654 1 : i.stats.ForwardStepCount[InternalIterCall]++
655 1 : if i.iterKey == nil || !i.equal(i.key, i.iterKey.UserKey) {
656 1 : i.pos = iterPosNext
657 1 : return false
658 1 : }
659 :
660 1 : key := *i.iterKey
661 1 : switch key.Kind() {
662 0 : case InternalKeyKindRangeKeySet:
663 0 : // RangeKeySets must always be interleaved as the first internal key
664 0 : // for a user key.
665 0 : i.err = base.CorruptionErrorf("pebble: unexpected range key set mid-user key")
666 0 : return false
667 :
668 1 : case InternalKeyKindDelete, InternalKeyKindSingleDelete, InternalKeyKindDeleteSized:
669 1 : // NB: treating InternalKeyKindSingleDelete as equivalent to DEL is not
670 1 : // only simpler, but is also necessary for correctness due to
671 1 : // InternalKeyKindSSTableInternalObsoleteBit.
672 1 : return false
673 :
674 1 : case InternalKeyKindSet, InternalKeyKindSetWithDelete:
675 1 : i.value = i.iterValue
676 1 : return true
677 :
678 1 : case InternalKeyKindMerge:
679 1 : return i.mergeForward(key)
680 :
681 0 : default:
682 0 : i.err = base.CorruptionErrorf("pebble: invalid internal key kind: %d", errors.Safe(key.Kind()))
683 0 : return false
684 : }
685 : }
686 :
687 : // mergeForward resolves a MERGE key, advancing the underlying iterator forward
688 : // to merge with subsequent keys with the same userkey. mergeForward returns a
689 : // boolean indicating whether or not the merge yielded a valid key. A merge may
690 : // not yield a valid key if an error occurred, in which case i.err is non-nil,
691 : // or the user's value merger specified the key to be deleted.
692 : //
693 : // mergeForward does not update iterValidityState.
694 1 : func (i *Iterator) mergeForward(key base.InternalKey) (valid bool) {
695 1 : var iterValue []byte
696 1 : iterValue, _, i.err = i.iterValue.Value(nil)
697 1 : if i.err != nil {
698 0 : return false
699 0 : }
700 1 : var valueMerger ValueMerger
701 1 : valueMerger, i.err = i.merge(key.UserKey, iterValue)
702 1 : if i.err != nil {
703 0 : return false
704 0 : }
705 :
706 1 : i.mergeNext(key, valueMerger)
707 1 : if i.err != nil {
708 0 : return false
709 0 : }
710 :
711 1 : var needDelete bool
712 1 : var value []byte
713 1 : value, needDelete, i.valueCloser, i.err = finishValueMerger(
714 1 : valueMerger, true /* includesBase */)
715 1 : i.value = base.MakeInPlaceValue(value)
716 1 : if i.err != nil {
717 0 : return false
718 0 : }
719 1 : if needDelete {
720 1 : _ = i.closeValueCloser()
721 1 : return false
722 1 : }
723 1 : return true
724 : }
725 :
726 1 : func (i *Iterator) closeValueCloser() error {
727 1 : if i.valueCloser != nil {
728 0 : i.err = i.valueCloser.Close()
729 0 : i.valueCloser = nil
730 0 : }
731 1 : return i.err
732 : }
733 :
734 1 : func (i *Iterator) nextUserKey() {
735 1 : if i.iterKey == nil {
736 1 : return
737 1 : }
738 1 : trailer := i.iterKey.Trailer
739 1 : done := i.iterKey.Trailer <= base.InternalKeyZeroSeqnumMaxTrailer
740 1 : if i.iterValidityState != IterValid {
741 1 : i.keyBuf = append(i.keyBuf[:0], i.iterKey.UserKey...)
742 1 : i.key = i.keyBuf
743 1 : }
744 1 : for {
745 1 : i.iterKey, i.iterValue = i.iter.Next()
746 1 : i.stats.ForwardStepCount[InternalIterCall]++
747 1 : // NB: We're guaranteed to be on the next user key if the previous key
748 1 : // had a zero sequence number (`done`), or the new key has a trailer
749 1 : // greater or equal to the previous key's trailer. This is true because
750 1 : // internal keys with the same user key are sorted by Trailer in
751 1 : // strictly monotonically descending order. We expect the trailer
752 1 : // optimization to trigger around 50% of the time with randomly
753 1 : // distributed writes. We expect it to trigger very frequently when
754 1 : // iterating through ingested sstables, which contain keys that all have
755 1 : // the same sequence number.
756 1 : if done || i.iterKey == nil || i.iterKey.Trailer >= trailer {
757 1 : break
758 : }
759 1 : if !i.equal(i.key, i.iterKey.UserKey) {
760 1 : break
761 : }
762 1 : done = i.iterKey.Trailer <= base.InternalKeyZeroSeqnumMaxTrailer
763 1 : trailer = i.iterKey.Trailer
764 : }
765 : }
766 :
767 1 : func (i *Iterator) maybeSampleRead() {
768 1 : // This method is only called when a public method of Iterator is
769 1 : // returning, and below we exclude the case were the iterator is paused at
770 1 : // a limit. The effect of these choices is that keys that are deleted, but
771 1 : // are encountered during iteration, are not accounted for in the read
772 1 : // sampling and will not cause read driven compactions, even though we are
773 1 : // incurring cost in iterating over them. And this issue is not limited to
774 1 : // Iterator, which does not see the effect of range deletes, which may be
775 1 : // causing iteration work in mergingIter. It is not clear at this time
776 1 : // whether this is a deficiency worth addressing.
777 1 : if i.iterValidityState != IterValid {
778 1 : return
779 1 : }
780 1 : if i.readState == nil {
781 1 : return
782 1 : }
783 1 : if i.readSampling.forceReadSampling {
784 1 : i.sampleRead()
785 1 : return
786 1 : }
787 1 : samplingPeriod := int32(int64(readBytesPeriod) * i.readState.db.opts.Experimental.ReadSamplingMultiplier)
788 1 : if samplingPeriod <= 0 {
789 0 : return
790 0 : }
791 1 : bytesRead := uint64(len(i.key) + i.value.Len())
792 1 : for i.readSampling.bytesUntilReadSampling < bytesRead {
793 1 : i.readSampling.bytesUntilReadSampling += uint64(fastrand.Uint32n(2 * uint32(samplingPeriod)))
794 1 : // The block below tries to adjust for the case where this is the
795 1 : // first read in a newly-opened iterator. As bytesUntilReadSampling
796 1 : // starts off at zero, we don't want to sample the first read of
797 1 : // every newly-opened iterator, but we do want to sample some of them.
798 1 : if !i.readSampling.initialSamplePassed {
799 1 : i.readSampling.initialSamplePassed = true
800 1 : if fastrand.Uint32n(uint32(i.readSampling.bytesUntilReadSampling)) > uint32(bytesRead) {
801 1 : continue
802 : }
803 : }
804 1 : i.sampleRead()
805 : }
806 1 : i.readSampling.bytesUntilReadSampling -= bytesRead
807 : }
808 :
809 1 : func (i *Iterator) sampleRead() {
810 1 : var topFile *manifest.FileMetadata
811 1 : topLevel, numOverlappingLevels := numLevels, 0
812 1 : mi := i.merging
813 1 : if mi == nil {
814 1 : return
815 1 : }
816 1 : if len(mi.levels) > 1 {
817 1 : mi.ForEachLevelIter(func(li *levelIter) bool {
818 1 : l := manifest.LevelToInt(li.level)
819 1 : if f := li.iterFile; f != nil {
820 1 : var containsKey bool
821 1 : if i.pos == iterPosNext || i.pos == iterPosCurForward ||
822 1 : i.pos == iterPosCurForwardPaused {
823 1 : containsKey = i.cmp(f.SmallestPointKey.UserKey, i.key) <= 0
824 1 : } else if i.pos == iterPosPrev || i.pos == iterPosCurReverse ||
825 1 : i.pos == iterPosCurReversePaused {
826 1 : containsKey = i.cmp(f.LargestPointKey.UserKey, i.key) >= 0
827 1 : }
828 : // Do nothing if the current key is not contained in f's
829 : // bounds. We could seek the LevelIterator at this level
830 : // to find the right file, but the performance impacts of
831 : // doing that are significant enough to negate the benefits
832 : // of read sampling in the first place. See the discussion
833 : // at:
834 : // https://github.com/cockroachdb/pebble/pull/1041#issuecomment-763226492
835 1 : if containsKey {
836 1 : numOverlappingLevels++
837 1 : if numOverlappingLevels >= 2 {
838 1 : // Terminate the loop early if at least 2 overlapping levels are found.
839 1 : return true
840 1 : }
841 1 : topLevel = l
842 1 : topFile = f
843 : }
844 : }
845 1 : return false
846 : })
847 : }
848 1 : if topFile == nil || topLevel >= numLevels {
849 1 : return
850 1 : }
851 1 : if numOverlappingLevels >= 2 {
852 1 : allowedSeeks := topFile.AllowedSeeks.Add(-1)
853 1 : if allowedSeeks == 0 {
854 1 :
855 1 : // Since the compaction queue can handle duplicates, we can keep
856 1 : // adding to the queue even once allowedSeeks hits 0.
857 1 : // In fact, we NEED to keep adding to the queue, because the queue
858 1 : // is small and evicts older and possibly useful compactions.
859 1 : topFile.AllowedSeeks.Add(topFile.InitAllowedSeeks)
860 1 :
861 1 : read := readCompaction{
862 1 : start: topFile.SmallestPointKey.UserKey,
863 1 : end: topFile.LargestPointKey.UserKey,
864 1 : level: topLevel,
865 1 : fileNum: topFile.FileNum,
866 1 : }
867 1 : i.readSampling.pendingCompactions.add(&read, i.cmp)
868 1 : }
869 : }
870 : }
871 :
872 1 : func (i *Iterator) findPrevEntry(limit []byte) {
873 1 : i.iterValidityState = IterExhausted
874 1 : i.pos = iterPosCurReverse
875 1 : if i.opts.rangeKeys() && i.rangeKey != nil {
876 1 : i.rangeKey.rangeKeyOnly = false
877 1 : }
878 :
879 : // Close the closer for the current value if one was open.
880 1 : if i.valueCloser != nil {
881 0 : i.err = i.valueCloser.Close()
882 0 : i.valueCloser = nil
883 0 : if i.err != nil {
884 0 : i.iterValidityState = IterExhausted
885 0 : return
886 0 : }
887 : }
888 :
889 1 : var valueMerger ValueMerger
890 1 : firstLoopIter := true
891 1 : rangeKeyBoundary := false
892 1 : // The code below compares with limit in multiple places. As documented in
893 1 : // findNextEntry, this is being done to make the behavior of limit
894 1 : // deterministic to allow for metamorphic testing. It is not required by
895 1 : // the best-effort contract of limit.
896 1 : for i.iterKey != nil {
897 1 : key := *i.iterKey
898 1 :
899 1 : // NB: We cannot pause if the current key is covered by a range key.
900 1 : // Otherwise, the user might not ever learn of a range key that covers
901 1 : // the key space being iterated over in which there are no point keys.
902 1 : // Since limits are best effort, ignoring the limit in this case is
903 1 : // allowed by the contract of limit.
904 1 : if firstLoopIter && limit != nil && i.cmp(limit, i.iterKey.UserKey) > 0 && !i.rangeKeyWithinLimit(limit) {
905 1 : i.iterValidityState = IterAtLimit
906 1 : i.pos = iterPosCurReversePaused
907 1 : return
908 1 : }
909 1 : firstLoopIter = false
910 1 :
911 1 : if i.iterValidityState == IterValid {
912 1 : if !i.equal(key.UserKey, i.key) {
913 1 : // We've iterated to the previous user key.
914 1 : i.pos = iterPosPrev
915 1 : if valueMerger != nil {
916 1 : var needDelete bool
917 1 : var value []byte
918 1 : value, needDelete, i.valueCloser, i.err = finishValueMerger(valueMerger, true /* includesBase */)
919 1 : i.value = base.MakeInPlaceValue(value)
920 1 : if i.err == nil && needDelete {
921 1 : // The point key at this key is deleted. If we also have
922 1 : // a range key boundary at this key, we still want to
923 1 : // return. Otherwise, we need to continue looking for
924 1 : // a live key.
925 1 : i.value = LazyValue{}
926 1 : if rangeKeyBoundary {
927 0 : i.rangeKey.rangeKeyOnly = true
928 1 : } else {
929 1 : i.iterValidityState = IterExhausted
930 1 : if i.closeValueCloser() == nil {
931 1 : continue
932 : }
933 : }
934 : }
935 : }
936 1 : if i.err != nil {
937 0 : i.iterValidityState = IterExhausted
938 0 : }
939 1 : return
940 : }
941 : }
942 :
943 : // If the user has configured a SkipPoint function, invoke it to see
944 : // whether we should skip over the current user key.
945 1 : if i.opts.SkipPoint != nil && key.Kind() != InternalKeyKindRangeKeySet && i.opts.SkipPoint(key.UserKey) {
946 1 : // NB: We could call prevUserKey, but in some cases the SkipPoint
947 1 : // predicate function might be cheaper than prevUserKey's key copy
948 1 : // and key comparison. This should be the case for MVCC suffix
949 1 : // comparisons, for example. In the future, we could expand the
950 1 : // SkipPoint interface to give the implementor more control over
951 1 : // whether we skip over just the internal key, the user key, or even
952 1 : // the key prefix.
953 1 : i.stats.ReverseStepCount[InternalIterCall]++
954 1 : i.iterKey, i.iterValue = i.iter.Prev()
955 1 : if limit != nil && i.iterKey != nil && i.cmp(limit, i.iterKey.UserKey) > 0 && !i.rangeKeyWithinLimit(limit) {
956 1 : i.iterValidityState = IterAtLimit
957 1 : i.pos = iterPosCurReversePaused
958 1 : return
959 1 : }
960 1 : continue
961 : }
962 :
963 1 : switch key.Kind() {
964 1 : case InternalKeyKindRangeKeySet:
965 1 : // Range key start boundary markers are interleaved with the maximum
966 1 : // sequence number, so if there's a point key also at this key, we
967 1 : // must've already iterated over it.
968 1 : // This is the final entry at this user key, so we may return
969 1 : i.rangeKey.rangeKeyOnly = i.iterValidityState != IterValid
970 1 : i.keyBuf = append(i.keyBuf[:0], key.UserKey...)
971 1 : i.key = i.keyBuf
972 1 : i.iterValidityState = IterValid
973 1 : i.saveRangeKey()
974 1 : // In all other cases, previous iteration requires advancing to
975 1 : // iterPosPrev in order to determine if the key is live and
976 1 : // unshadowed by another key at the same user key. In this case,
977 1 : // because range key start boundary markers are always interleaved
978 1 : // at the maximum sequence number, we know that there aren't any
979 1 : // additional keys with the same user key in the backward direction.
980 1 : //
981 1 : // We Prev the underlying iterator once anyways for consistency, so
982 1 : // that we can maintain the invariant during backward iteration that
983 1 : // i.iterPos = iterPosPrev.
984 1 : i.stats.ReverseStepCount[InternalIterCall]++
985 1 : i.iterKey, i.iterValue = i.iter.Prev()
986 1 :
987 1 : // Set rangeKeyBoundary so that on the next iteration, we know to
988 1 : // return the key even if the MERGE point key is deleted.
989 1 : rangeKeyBoundary = true
990 :
991 1 : case InternalKeyKindDelete, InternalKeyKindSingleDelete, InternalKeyKindDeleteSized:
992 1 : i.value = LazyValue{}
993 1 : i.iterValidityState = IterExhausted
994 1 : valueMerger = nil
995 1 : i.iterKey, i.iterValue = i.iter.Prev()
996 1 : i.stats.ReverseStepCount[InternalIterCall]++
997 1 : // Compare with the limit. We could optimize by only checking when
998 1 : // we step to the previous user key, but detecting that requires a
999 1 : // comparison too. Note that this position may already passed a
1000 1 : // number of versions of this user key, but they are all deleted, so
1001 1 : // the fact that a subsequent Prev*() call will not see them is
1002 1 : // harmless. Also note that this is the only place in the loop,
1003 1 : // other than the firstLoopIter and SkipPoint cases above, where we
1004 1 : // could step to a different user key and start processing it for
1005 1 : // returning to the caller.
1006 1 : if limit != nil && i.iterKey != nil && i.cmp(limit, i.iterKey.UserKey) > 0 && !i.rangeKeyWithinLimit(limit) {
1007 1 : i.iterValidityState = IterAtLimit
1008 1 : i.pos = iterPosCurReversePaused
1009 1 : return
1010 1 : }
1011 1 : continue
1012 :
1013 1 : case InternalKeyKindSet, InternalKeyKindSetWithDelete:
1014 1 : i.keyBuf = append(i.keyBuf[:0], key.UserKey...)
1015 1 : i.key = i.keyBuf
1016 1 : // iterValue is owned by i.iter and could change after the Prev()
1017 1 : // call, so use valueBuf instead. Note that valueBuf is only used
1018 1 : // in this one instance; everywhere else (eg. in findNextEntry),
1019 1 : // we just point i.value to the unsafe i.iter-owned value buffer.
1020 1 : i.value, i.valueBuf = i.iterValue.Clone(i.valueBuf[:0], &i.fetcher)
1021 1 : i.saveRangeKey()
1022 1 : i.iterValidityState = IterValid
1023 1 : i.iterKey, i.iterValue = i.iter.Prev()
1024 1 : i.stats.ReverseStepCount[InternalIterCall]++
1025 1 : valueMerger = nil
1026 1 : continue
1027 :
1028 1 : case InternalKeyKindMerge:
1029 1 : if i.iterValidityState == IterExhausted {
1030 1 : i.keyBuf = append(i.keyBuf[:0], key.UserKey...)
1031 1 : i.key = i.keyBuf
1032 1 : i.saveRangeKey()
1033 1 : var iterValue []byte
1034 1 : iterValue, _, i.err = i.iterValue.Value(nil)
1035 1 : if i.err != nil {
1036 0 : return
1037 0 : }
1038 1 : valueMerger, i.err = i.merge(i.key, iterValue)
1039 1 : if i.err != nil {
1040 0 : return
1041 0 : }
1042 1 : i.iterValidityState = IterValid
1043 1 : } else if valueMerger == nil {
1044 1 : // Extract value before iterValue since we use value before iterValue
1045 1 : // and the underlying iterator is not required to provide backing
1046 1 : // memory for both simultaneously.
1047 1 : var value []byte
1048 1 : var callerOwned bool
1049 1 : value, callerOwned, i.err = i.value.Value(i.lazyValueBuf)
1050 1 : if callerOwned {
1051 0 : i.lazyValueBuf = value[:0]
1052 0 : }
1053 1 : if i.err != nil {
1054 0 : return
1055 0 : }
1056 1 : valueMerger, i.err = i.merge(i.key, value)
1057 1 : var iterValue []byte
1058 1 : iterValue, _, i.err = i.iterValue.Value(nil)
1059 1 : if i.err != nil {
1060 0 : return
1061 0 : }
1062 1 : if i.err == nil {
1063 1 : i.err = valueMerger.MergeNewer(iterValue)
1064 1 : }
1065 1 : if i.err != nil {
1066 0 : i.iterValidityState = IterExhausted
1067 0 : return
1068 0 : }
1069 1 : } else {
1070 1 : var iterValue []byte
1071 1 : iterValue, _, i.err = i.iterValue.Value(nil)
1072 1 : if i.err != nil {
1073 0 : return
1074 0 : }
1075 1 : i.err = valueMerger.MergeNewer(iterValue)
1076 1 : if i.err != nil {
1077 0 : i.iterValidityState = IterExhausted
1078 0 : return
1079 0 : }
1080 : }
1081 1 : i.iterKey, i.iterValue = i.iter.Prev()
1082 1 : i.stats.ReverseStepCount[InternalIterCall]++
1083 1 : continue
1084 :
1085 0 : default:
1086 0 : i.err = base.CorruptionErrorf("pebble: invalid internal key kind: %d", errors.Safe(key.Kind()))
1087 0 : i.iterValidityState = IterExhausted
1088 0 : return
1089 : }
1090 : }
1091 :
1092 : // i.iterKey == nil, so broke out of the preceding loop.
1093 1 : if i.iterValidityState == IterValid {
1094 1 : i.pos = iterPosPrev
1095 1 : if valueMerger != nil {
1096 1 : var needDelete bool
1097 1 : var value []byte
1098 1 : value, needDelete, i.valueCloser, i.err = finishValueMerger(valueMerger, true /* includesBase */)
1099 1 : i.value = base.MakeInPlaceValue(value)
1100 1 : if i.err == nil && needDelete {
1101 1 : i.key = nil
1102 1 : i.value = LazyValue{}
1103 1 : i.iterValidityState = IterExhausted
1104 1 : }
1105 : }
1106 1 : if i.err != nil {
1107 0 : i.iterValidityState = IterExhausted
1108 0 : }
1109 : }
1110 : }
1111 :
1112 1 : func (i *Iterator) prevUserKey() {
1113 1 : if i.iterKey == nil {
1114 1 : return
1115 1 : }
1116 1 : if i.iterValidityState != IterValid {
1117 1 : // If we're going to compare against the prev key, we need to save the
1118 1 : // current key.
1119 1 : i.keyBuf = append(i.keyBuf[:0], i.iterKey.UserKey...)
1120 1 : i.key = i.keyBuf
1121 1 : }
1122 1 : for {
1123 1 : i.iterKey, i.iterValue = i.iter.Prev()
1124 1 : i.stats.ReverseStepCount[InternalIterCall]++
1125 1 : if i.iterKey == nil {
1126 1 : break
1127 : }
1128 1 : if !i.equal(i.key, i.iterKey.UserKey) {
1129 1 : break
1130 : }
1131 : }
1132 : }
1133 :
1134 1 : func (i *Iterator) mergeNext(key InternalKey, valueMerger ValueMerger) {
1135 1 : // Save the current key.
1136 1 : i.keyBuf = append(i.keyBuf[:0], key.UserKey...)
1137 1 : i.key = i.keyBuf
1138 1 :
1139 1 : // Loop looking for older values for this key and merging them.
1140 1 : for {
1141 1 : i.iterKey, i.iterValue = i.iter.Next()
1142 1 : i.stats.ForwardStepCount[InternalIterCall]++
1143 1 : if i.iterKey == nil {
1144 1 : i.pos = iterPosNext
1145 1 : return
1146 1 : }
1147 1 : key = *i.iterKey
1148 1 : if !i.equal(i.key, key.UserKey) {
1149 1 : // We've advanced to the next key.
1150 1 : i.pos = iterPosNext
1151 1 : return
1152 1 : }
1153 1 : switch key.Kind() {
1154 1 : case InternalKeyKindDelete, InternalKeyKindSingleDelete, InternalKeyKindDeleteSized:
1155 1 : // We've hit a deletion tombstone. Return everything up to this
1156 1 : // point.
1157 1 : //
1158 1 : // NB: treating InternalKeyKindSingleDelete as equivalent to DEL is not
1159 1 : // only simpler, but is also necessary for correctness due to
1160 1 : // InternalKeyKindSSTableInternalObsoleteBit.
1161 1 : return
1162 :
1163 1 : case InternalKeyKindSet, InternalKeyKindSetWithDelete:
1164 1 : // We've hit a Set value. Merge with the existing value and return.
1165 1 : var iterValue []byte
1166 1 : iterValue, _, i.err = i.iterValue.Value(nil)
1167 1 : if i.err != nil {
1168 0 : return
1169 0 : }
1170 1 : i.err = valueMerger.MergeOlder(iterValue)
1171 1 : return
1172 :
1173 1 : case InternalKeyKindMerge:
1174 1 : // We've hit another Merge value. Merge with the existing value and
1175 1 : // continue looping.
1176 1 : var iterValue []byte
1177 1 : iterValue, _, i.err = i.iterValue.Value(nil)
1178 1 : if i.err != nil {
1179 0 : return
1180 0 : }
1181 1 : i.err = valueMerger.MergeOlder(iterValue)
1182 1 : if i.err != nil {
1183 0 : return
1184 0 : }
1185 1 : continue
1186 :
1187 0 : case InternalKeyKindRangeKeySet:
1188 0 : // The RANGEKEYSET marker must sort before a MERGE at the same user key.
1189 0 : i.err = base.CorruptionErrorf("pebble: out of order range key marker")
1190 0 : return
1191 :
1192 0 : default:
1193 0 : i.err = base.CorruptionErrorf("pebble: invalid internal key kind: %d", errors.Safe(key.Kind()))
1194 0 : return
1195 : }
1196 : }
1197 : }
1198 :
1199 : // SeekGE moves the iterator to the first key/value pair whose key is greater
1200 : // than or equal to the given key. Returns true if the iterator is pointing at
1201 : // a valid entry and false otherwise.
1202 1 : func (i *Iterator) SeekGE(key []byte) bool {
1203 1 : return i.SeekGEWithLimit(key, nil) == IterValid
1204 1 : }
1205 :
1206 : // SeekGEWithLimit moves the iterator to the first key/value pair whose key is
1207 : // greater than or equal to the given key.
1208 : //
1209 : // If limit is provided, it serves as a best-effort exclusive limit. If the
1210 : // first key greater than or equal to the given search key is also greater than
1211 : // or equal to limit, the Iterator may pause and return IterAtLimit. Because
1212 : // limits are best-effort, SeekGEWithLimit may return a key beyond limit.
1213 : //
1214 : // If the Iterator is configured to iterate over range keys, SeekGEWithLimit
1215 : // guarantees it will surface any range keys with bounds overlapping the
1216 : // keyspace [key, limit).
1217 1 : func (i *Iterator) SeekGEWithLimit(key []byte, limit []byte) IterValidityState {
1218 1 : if i.rangeKey != nil {
1219 1 : // NB: Check Valid() before clearing requiresReposition.
1220 1 : i.rangeKey.prevPosHadRangeKey = i.rangeKey.hasRangeKey && i.Valid()
1221 1 : // If we have a range key but did not expose it at the previous iterator
1222 1 : // position (because the iterator was not at a valid position), updated
1223 1 : // must be true. This ensures that after an iterator op sequence like:
1224 1 : // - Next() → (IterValid, RangeBounds() = [a,b))
1225 1 : // - NextWithLimit(...) → (IterAtLimit, RangeBounds() = -)
1226 1 : // - SeekGE(...) → (IterValid, RangeBounds() = [a,b))
1227 1 : // the iterator returns RangeKeyChanged()=true.
1228 1 : //
1229 1 : // The remainder of this function will only update i.rangeKey.updated if
1230 1 : // the iterator moves into a new range key, or out of the current range
1231 1 : // key.
1232 1 : i.rangeKey.updated = i.rangeKey.hasRangeKey && !i.Valid() && i.opts.rangeKeys()
1233 1 : }
1234 1 : lastPositioningOp := i.lastPositioningOp
1235 1 : hasPrefix := i.hasPrefix
1236 1 : // Set it to unknown, since this operation may not succeed, in which case
1237 1 : // the SeekGE following this should not make any assumption about iterator
1238 1 : // position.
1239 1 : i.lastPositioningOp = unknownLastPositionOp
1240 1 : i.requiresReposition = false
1241 1 : i.err = nil // clear cached iteration error
1242 1 : i.hasPrefix = false
1243 1 : i.stats.ForwardSeekCount[InterfaceCall]++
1244 1 : if lowerBound := i.opts.GetLowerBound(); lowerBound != nil && i.cmp(key, lowerBound) < 0 {
1245 1 : key = lowerBound
1246 1 : } else if upperBound := i.opts.GetUpperBound(); upperBound != nil && i.cmp(key, upperBound) > 0 {
1247 1 : key = upperBound
1248 1 : }
1249 1 : seekInternalIter := true
1250 1 :
1251 1 : var flags base.SeekGEFlags
1252 1 : if i.batchJustRefreshed {
1253 1 : i.batchJustRefreshed = false
1254 1 : flags = flags.EnableBatchJustRefreshed()
1255 1 : }
1256 1 : if lastPositioningOp == seekGELastPositioningOp {
1257 1 : cmp := i.cmp(i.prefixOrFullSeekKey, key)
1258 1 : // If this seek is to the same or later key, and the iterator is
1259 1 : // already positioned there, this is a noop. This can be helpful for
1260 1 : // sparse key spaces that have many deleted keys, where one can avoid
1261 1 : // the overhead of iterating past them again and again.
1262 1 : if cmp <= 0 {
1263 1 : if !flags.BatchJustRefreshed() &&
1264 1 : (i.iterValidityState == IterExhausted ||
1265 1 : (i.iterValidityState == IterValid && i.cmp(key, i.key) <= 0 &&
1266 1 : (limit == nil || i.cmp(i.key, limit) < 0))) {
1267 1 : // Noop
1268 1 : if !invariants.Enabled || !disableSeekOpt(key, uintptr(unsafe.Pointer(i))) || i.forceEnableSeekOpt {
1269 1 : i.lastPositioningOp = seekGELastPositioningOp
1270 1 : return i.iterValidityState
1271 1 : }
1272 : }
1273 : // cmp == 0 is not safe to optimize since
1274 : // - i.pos could be at iterPosNext, due to a merge.
1275 : // - Even if i.pos were at iterPosCurForward, we could have a DELETE,
1276 : // SET pair for a key, and the iterator would have moved past DELETE
1277 : // but stayed at iterPosCurForward. A similar situation occurs for a
1278 : // MERGE, SET pair where the MERGE is consumed and the iterator is
1279 : // at the SET.
1280 : // We also leverage the IterAtLimit <=> i.pos invariant defined in the
1281 : // comment on iterValidityState, to exclude any cases where i.pos
1282 : // is iterPosCur{Forward,Reverse}Paused. This avoids the need to
1283 : // special-case those iterator positions and their interactions with
1284 : // TrySeekUsingNext, as the main uses for TrySeekUsingNext in CockroachDB
1285 : // do not use limited Seeks in the first place.
1286 1 : if cmp < 0 && i.iterValidityState != IterAtLimit && limit == nil {
1287 1 : flags = flags.EnableTrySeekUsingNext()
1288 1 : }
1289 1 : if invariants.Enabled && flags.TrySeekUsingNext() && !i.forceEnableSeekOpt && disableSeekOpt(key, uintptr(unsafe.Pointer(i))) {
1290 1 : flags = flags.DisableTrySeekUsingNext()
1291 1 : }
1292 1 : if !flags.BatchJustRefreshed() && i.pos == iterPosCurForwardPaused && i.cmp(key, i.iterKey.UserKey) <= 0 {
1293 1 : // Have some work to do, but don't need to seek, and we can
1294 1 : // start doing findNextEntry from i.iterKey.
1295 1 : seekInternalIter = false
1296 1 : }
1297 : }
1298 : }
1299 : // Check for another TrySeekUsingNext optimization opportunity, currently
1300 : // specifically tailored to external iterators. This case is intended to
1301 : // trigger in instances of Seek-ing with monotonically increasing keys with
1302 : // Nexts interspersed. At the time of writing, this is the case for
1303 : // CockroachDB scans. This optimization is important for external iterators
1304 : // to avoid re-seeking within an already-exhausted sstable. It is not always
1305 : // a performance win more generally, so we restrict it to external iterators
1306 : // that are configured to only use forward positioning operations.
1307 : //
1308 : // TODO(jackson): This optimization should be obsolete once we introduce and
1309 : // use the NextPrefix iterator positioning operation.
1310 1 : if seekInternalIter && i.forwardOnly && lastPositioningOp != invalidatedLastPositionOp &&
1311 1 : i.pos == iterPosCurForward && !hasPrefix && i.iterValidityState == IterValid &&
1312 1 : i.cmp(key, i.iterKey.UserKey) > 0 {
1313 1 : flags = flags.EnableTrySeekUsingNext()
1314 1 : if invariants.Enabled && flags.TrySeekUsingNext() && !i.forceEnableSeekOpt && disableSeekOpt(key, uintptr(unsafe.Pointer(i))) {
1315 0 : flags = flags.DisableTrySeekUsingNext()
1316 0 : }
1317 : }
1318 1 : if seekInternalIter {
1319 1 : i.iterKey, i.iterValue = i.iter.SeekGE(key, flags)
1320 1 : i.stats.ForwardSeekCount[InternalIterCall]++
1321 1 : }
1322 1 : i.findNextEntry(limit)
1323 1 : i.maybeSampleRead()
1324 1 : if i.Error() == nil {
1325 1 : // Prepare state for a future noop optimization.
1326 1 : i.prefixOrFullSeekKey = append(i.prefixOrFullSeekKey[:0], key...)
1327 1 : i.lastPositioningOp = seekGELastPositioningOp
1328 1 : }
1329 1 : return i.iterValidityState
1330 : }
1331 :
1332 : // SeekPrefixGE moves the iterator to the first key/value pair whose key is
1333 : // greater than or equal to the given key and which has the same "prefix" as
1334 : // the given key. The prefix for a key is determined by the user-defined
1335 : // Comparer.Split function. The iterator will not observe keys not matching the
1336 : // "prefix" of the search key. Calling SeekPrefixGE puts the iterator in prefix
1337 : // iteration mode. The iterator remains in prefix iteration until a subsequent
1338 : // call to another absolute positioning method (SeekGE, SeekLT, First,
1339 : // Last). Reverse iteration (Prev) is not supported when an iterator is in
1340 : // prefix iteration mode. Returns true if the iterator is pointing at a valid
1341 : // entry and false otherwise.
1342 : //
1343 : // The semantics of SeekPrefixGE are slightly unusual and designed for
1344 : // iteration to be able to take advantage of bloom filters that have been
1345 : // created on the "prefix". If you're not using bloom filters, there is no
1346 : // reason to use SeekPrefixGE.
1347 : //
1348 : // An example Split function may separate a timestamp suffix from the prefix of
1349 : // the key.
1350 : //
1351 : // Split(<key>@<timestamp>) -> <key>
1352 : //
1353 : // Consider the keys "a@1", "a@2", "aa@3", "aa@4". The prefixes for these keys
1354 : // are "a", and "aa". Note that despite "a" and "aa" sharing a prefix by the
1355 : // usual definition, those prefixes differ by the definition of the Split
1356 : // function. To see how this works, consider the following set of calls on this
1357 : // data set:
1358 : //
1359 : // SeekPrefixGE("a@0") -> "a@1"
1360 : // Next() -> "a@2"
1361 : // Next() -> EOF
1362 : //
1363 : // If you're just looking to iterate over keys with a shared prefix, as
1364 : // defined by the configured comparer, set iterator bounds instead:
1365 : //
1366 : // iter := db.NewIter(&pebble.IterOptions{
1367 : // LowerBound: []byte("prefix"),
1368 : // UpperBound: []byte("prefiy"),
1369 : // })
1370 : // for iter.First(); iter.Valid(); iter.Next() {
1371 : // // Only keys beginning with "prefix" will be visited.
1372 : // }
1373 : //
1374 : // See ExampleIterator_SeekPrefixGE for a working example.
1375 : //
1376 : // When iterating with range keys enabled, all range keys encountered are
1377 : // truncated to the seek key's prefix's bounds. The truncation of the upper
1378 : // bound requires that the database's Comparer is configured with a
1379 : // ImmediateSuccessor method. For example, a SeekPrefixGE("a@9") call with the
1380 : // prefix "a" will truncate range key bounds to [a,ImmediateSuccessor(a)].
1381 1 : func (i *Iterator) SeekPrefixGE(key []byte) bool {
1382 1 : if i.rangeKey != nil {
1383 1 : // NB: Check Valid() before clearing requiresReposition.
1384 1 : i.rangeKey.prevPosHadRangeKey = i.rangeKey.hasRangeKey && i.Valid()
1385 1 : // If we have a range key but did not expose it at the previous iterator
1386 1 : // position (because the iterator was not at a valid position), updated
1387 1 : // must be true. This ensures that after an iterator op sequence like:
1388 1 : // - Next() → (IterValid, RangeBounds() = [a,b))
1389 1 : // - NextWithLimit(...) → (IterAtLimit, RangeBounds() = -)
1390 1 : // - SeekPrefixGE(...) → (IterValid, RangeBounds() = [a,b))
1391 1 : // the iterator returns RangeKeyChanged()=true.
1392 1 : //
1393 1 : // The remainder of this function will only update i.rangeKey.updated if
1394 1 : // the iterator moves into a new range key, or out of the current range
1395 1 : // key.
1396 1 : i.rangeKey.updated = i.rangeKey.hasRangeKey && !i.Valid() && i.opts.rangeKeys()
1397 1 : }
1398 1 : lastPositioningOp := i.lastPositioningOp
1399 1 : // Set it to unknown, since this operation may not succeed, in which case
1400 1 : // the SeekPrefixGE following this should not make any assumption about
1401 1 : // iterator position.
1402 1 : i.lastPositioningOp = unknownLastPositionOp
1403 1 : i.requiresReposition = false
1404 1 : i.err = nil // clear cached iteration error
1405 1 : i.stats.ForwardSeekCount[InterfaceCall]++
1406 1 : if i.comparer.Split == nil {
1407 0 : panic("pebble: split must be provided for SeekPrefixGE")
1408 : }
1409 1 : if i.comparer.ImmediateSuccessor == nil && i.opts.KeyTypes != IterKeyTypePointsOnly {
1410 0 : panic("pebble: ImmediateSuccessor must be provided for SeekPrefixGE with range keys")
1411 : }
1412 1 : prefixLen := i.split(key)
1413 1 : keyPrefix := key[:prefixLen]
1414 1 : var flags base.SeekGEFlags
1415 1 : if i.batchJustRefreshed {
1416 1 : flags = flags.EnableBatchJustRefreshed()
1417 1 : i.batchJustRefreshed = false
1418 1 : }
1419 1 : if lastPositioningOp == seekPrefixGELastPositioningOp {
1420 1 : if !i.hasPrefix {
1421 0 : panic("lastPositioningOpsIsSeekPrefixGE is true, but hasPrefix is false")
1422 : }
1423 : // The iterator has not been repositioned after the last SeekPrefixGE.
1424 : // See if we are seeking to a larger key, since then we can optimize
1425 : // the seek by using next. Note that we could also optimize if Next
1426 : // has been called, if the iterator is not exhausted and the current
1427 : // position is <= the seek key. We are keeping this limited for now
1428 : // since such optimizations require care for correctness, and to not
1429 : // become de-optimizations (if one usually has to do all the next
1430 : // calls and then the seek). This SeekPrefixGE optimization
1431 : // specifically benefits CockroachDB.
1432 1 : cmp := i.cmp(i.prefixOrFullSeekKey, keyPrefix)
1433 1 : // cmp == 0 is not safe to optimize since
1434 1 : // - i.pos could be at iterPosNext, due to a merge.
1435 1 : // - Even if i.pos were at iterPosCurForward, we could have a DELETE,
1436 1 : // SET pair for a key, and the iterator would have moved past DELETE
1437 1 : // but stayed at iterPosCurForward. A similar situation occurs for a
1438 1 : // MERGE, SET pair where the MERGE is consumed and the iterator is
1439 1 : // at the SET.
1440 1 : // In general some versions of i.prefix could have been consumed by
1441 1 : // the iterator, so we only optimize for cmp < 0.
1442 1 : if cmp < 0 {
1443 1 : flags = flags.EnableTrySeekUsingNext()
1444 1 : }
1445 1 : if invariants.Enabled && flags.TrySeekUsingNext() && !i.forceEnableSeekOpt && disableSeekOpt(key, uintptr(unsafe.Pointer(i))) {
1446 1 : flags = flags.DisableTrySeekUsingNext()
1447 1 : }
1448 : }
1449 : // Make a copy of the prefix so that modifications to the key after
1450 : // SeekPrefixGE returns does not affect the stored prefix.
1451 1 : if cap(i.prefixOrFullSeekKey) < prefixLen {
1452 1 : i.prefixOrFullSeekKey = make([]byte, prefixLen)
1453 1 : } else {
1454 1 : i.prefixOrFullSeekKey = i.prefixOrFullSeekKey[:prefixLen]
1455 1 : }
1456 1 : i.hasPrefix = true
1457 1 : copy(i.prefixOrFullSeekKey, keyPrefix)
1458 1 :
1459 1 : if lowerBound := i.opts.GetLowerBound(); lowerBound != nil && i.cmp(key, lowerBound) < 0 {
1460 1 : if n := i.split(lowerBound); !bytes.Equal(i.prefixOrFullSeekKey, lowerBound[:n]) {
1461 1 : i.err = errors.New("pebble: SeekPrefixGE supplied with key outside of lower bound")
1462 1 : i.iterValidityState = IterExhausted
1463 1 : return false
1464 1 : }
1465 1 : key = lowerBound
1466 1 : } else if upperBound := i.opts.GetUpperBound(); upperBound != nil && i.cmp(key, upperBound) > 0 {
1467 1 : if n := i.split(upperBound); !bytes.Equal(i.prefixOrFullSeekKey, upperBound[:n]) {
1468 1 : i.err = errors.New("pebble: SeekPrefixGE supplied with key outside of upper bound")
1469 1 : i.iterValidityState = IterExhausted
1470 1 : return false
1471 1 : }
1472 0 : key = upperBound
1473 : }
1474 1 : i.iterKey, i.iterValue = i.iter.SeekPrefixGE(i.prefixOrFullSeekKey, key, flags)
1475 1 : i.stats.ForwardSeekCount[InternalIterCall]++
1476 1 : i.findNextEntry(nil)
1477 1 : i.maybeSampleRead()
1478 1 : if i.Error() == nil {
1479 1 : i.lastPositioningOp = seekPrefixGELastPositioningOp
1480 1 : }
1481 1 : return i.iterValidityState == IterValid
1482 : }
1483 :
1484 : // Deterministic disabling of the seek optimizations. It uses the iterator
1485 : // pointer, since we want diversity in iterator behavior for the same key. Used
1486 : // for tests.
1487 1 : func disableSeekOpt(key []byte, ptr uintptr) bool {
1488 1 : // Fibonacci hash https://probablydance.com/2018/06/16/fibonacci-hashing-the-optimization-that-the-world-forgot-or-a-better-alternative-to-integer-modulo/
1489 1 : simpleHash := (11400714819323198485 * uint64(ptr)) >> 63
1490 1 : return key != nil && key[0]&byte(1) == 0 && simpleHash == 0
1491 1 : }
1492 :
1493 : // SeekLT moves the iterator to the last key/value pair whose key is less than
1494 : // the given key. Returns true if the iterator is pointing at a valid entry and
1495 : // false otherwise.
1496 1 : func (i *Iterator) SeekLT(key []byte) bool {
1497 1 : return i.SeekLTWithLimit(key, nil) == IterValid
1498 1 : }
1499 :
1500 : // SeekLTWithLimit moves the iterator to the last key/value pair whose key is
1501 : // less than the given key.
1502 : //
1503 : // If limit is provided, it serves as a best-effort inclusive limit. If the last
1504 : // key less than the given search key is also less than limit, the Iterator may
1505 : // pause and return IterAtLimit. Because limits are best-effort, SeekLTWithLimit
1506 : // may return a key beyond limit.
1507 : //
1508 : // If the Iterator is configured to iterate over range keys, SeekLTWithLimit
1509 : // guarantees it will surface any range keys with bounds overlapping the
1510 : // keyspace up to limit.
1511 1 : func (i *Iterator) SeekLTWithLimit(key []byte, limit []byte) IterValidityState {
1512 1 : if i.rangeKey != nil {
1513 1 : // NB: Check Valid() before clearing requiresReposition.
1514 1 : i.rangeKey.prevPosHadRangeKey = i.rangeKey.hasRangeKey && i.Valid()
1515 1 : // If we have a range key but did not expose it at the previous iterator
1516 1 : // position (because the iterator was not at a valid position), updated
1517 1 : // must be true. This ensures that after an iterator op sequence like:
1518 1 : // - Next() → (IterValid, RangeBounds() = [a,b))
1519 1 : // - NextWithLimit(...) → (IterAtLimit, RangeBounds() = -)
1520 1 : // - SeekLTWithLimit(...) → (IterValid, RangeBounds() = [a,b))
1521 1 : // the iterator returns RangeKeyChanged()=true.
1522 1 : //
1523 1 : // The remainder of this function will only update i.rangeKey.updated if
1524 1 : // the iterator moves into a new range key, or out of the current range
1525 1 : // key.
1526 1 : i.rangeKey.updated = i.rangeKey.hasRangeKey && !i.Valid() && i.opts.rangeKeys()
1527 1 : }
1528 1 : lastPositioningOp := i.lastPositioningOp
1529 1 : // Set it to unknown, since this operation may not succeed, in which case
1530 1 : // the SeekLT following this should not make any assumption about iterator
1531 1 : // position.
1532 1 : i.lastPositioningOp = unknownLastPositionOp
1533 1 : i.batchJustRefreshed = false
1534 1 : i.requiresReposition = false
1535 1 : i.err = nil // clear cached iteration error
1536 1 : i.stats.ReverseSeekCount[InterfaceCall]++
1537 1 : if upperBound := i.opts.GetUpperBound(); upperBound != nil && i.cmp(key, upperBound) > 0 {
1538 1 : key = upperBound
1539 1 : } else if lowerBound := i.opts.GetLowerBound(); lowerBound != nil && i.cmp(key, lowerBound) < 0 {
1540 1 : key = lowerBound
1541 1 : }
1542 1 : i.hasPrefix = false
1543 1 : seekInternalIter := true
1544 1 : // The following noop optimization only applies when i.batch == nil, since
1545 1 : // an iterator over a batch is iterating over mutable data, that may have
1546 1 : // changed since the last seek.
1547 1 : if lastPositioningOp == seekLTLastPositioningOp && i.batch == nil {
1548 1 : cmp := i.cmp(key, i.prefixOrFullSeekKey)
1549 1 : // If this seek is to the same or earlier key, and the iterator is
1550 1 : // already positioned there, this is a noop. This can be helpful for
1551 1 : // sparse key spaces that have many deleted keys, where one can avoid
1552 1 : // the overhead of iterating past them again and again.
1553 1 : if cmp <= 0 {
1554 1 : // NB: when pos != iterPosCurReversePaused, the invariant
1555 1 : // documented earlier implies that iterValidityState !=
1556 1 : // IterAtLimit.
1557 1 : if i.iterValidityState == IterExhausted ||
1558 1 : (i.iterValidityState == IterValid && i.cmp(i.key, key) < 0 &&
1559 1 : (limit == nil || i.cmp(limit, i.key) <= 0)) {
1560 1 : if !invariants.Enabled || !disableSeekOpt(key, uintptr(unsafe.Pointer(i))) {
1561 1 : i.lastPositioningOp = seekLTLastPositioningOp
1562 1 : return i.iterValidityState
1563 1 : }
1564 : }
1565 1 : if i.pos == iterPosCurReversePaused && i.cmp(i.iterKey.UserKey, key) < 0 {
1566 1 : // Have some work to do, but don't need to seek, and we can
1567 1 : // start doing findPrevEntry from i.iterKey.
1568 1 : seekInternalIter = false
1569 1 : }
1570 : }
1571 : }
1572 1 : if seekInternalIter {
1573 1 : i.iterKey, i.iterValue = i.iter.SeekLT(key, base.SeekLTFlagsNone)
1574 1 : i.stats.ReverseSeekCount[InternalIterCall]++
1575 1 : }
1576 1 : i.findPrevEntry(limit)
1577 1 : i.maybeSampleRead()
1578 1 : if i.Error() == nil && i.batch == nil {
1579 1 : // Prepare state for a future noop optimization.
1580 1 : i.prefixOrFullSeekKey = append(i.prefixOrFullSeekKey[:0], key...)
1581 1 : i.lastPositioningOp = seekLTLastPositioningOp
1582 1 : }
1583 1 : return i.iterValidityState
1584 : }
1585 :
1586 : // First moves the iterator the the first key/value pair. Returns true if the
1587 : // iterator is pointing at a valid entry and false otherwise.
1588 1 : func (i *Iterator) First() bool {
1589 1 : if i.rangeKey != nil {
1590 1 : // NB: Check Valid() before clearing requiresReposition.
1591 1 : i.rangeKey.prevPosHadRangeKey = i.rangeKey.hasRangeKey && i.Valid()
1592 1 : // If we have a range key but did not expose it at the previous iterator
1593 1 : // position (because the iterator was not at a valid position), updated
1594 1 : // must be true. This ensures that after an iterator op sequence like:
1595 1 : // - Next() → (IterValid, RangeBounds() = [a,b))
1596 1 : // - NextWithLimit(...) → (IterAtLimit, RangeBounds() = -)
1597 1 : // - First(...) → (IterValid, RangeBounds() = [a,b))
1598 1 : // the iterator returns RangeKeyChanged()=true.
1599 1 : //
1600 1 : // The remainder of this function will only update i.rangeKey.updated if
1601 1 : // the iterator moves into a new range key, or out of the current range
1602 1 : // key.
1603 1 : i.rangeKey.updated = i.rangeKey.hasRangeKey && !i.Valid() && i.opts.rangeKeys()
1604 1 : }
1605 1 : i.err = nil // clear cached iteration error
1606 1 : i.hasPrefix = false
1607 1 : i.batchJustRefreshed = false
1608 1 : i.lastPositioningOp = unknownLastPositionOp
1609 1 : i.requiresReposition = false
1610 1 : i.stats.ForwardSeekCount[InterfaceCall]++
1611 1 :
1612 1 : i.iterFirstWithinBounds()
1613 1 : i.findNextEntry(nil)
1614 1 : i.maybeSampleRead()
1615 1 : return i.iterValidityState == IterValid
1616 : }
1617 :
1618 : // Last moves the iterator the the last key/value pair. Returns true if the
1619 : // iterator is pointing at a valid entry and false otherwise.
1620 1 : func (i *Iterator) Last() bool {
1621 1 : if i.rangeKey != nil {
1622 1 : // NB: Check Valid() before clearing requiresReposition.
1623 1 : i.rangeKey.prevPosHadRangeKey = i.rangeKey.hasRangeKey && i.Valid()
1624 1 : // If we have a range key but did not expose it at the previous iterator
1625 1 : // position (because the iterator was not at a valid position), updated
1626 1 : // must be true. This ensures that after an iterator op sequence like:
1627 1 : // - Next() → (IterValid, RangeBounds() = [a,b))
1628 1 : // - NextWithLimit(...) → (IterAtLimit, RangeBounds() = -)
1629 1 : // - Last(...) → (IterValid, RangeBounds() = [a,b))
1630 1 : // the iterator returns RangeKeyChanged()=true.
1631 1 : //
1632 1 : // The remainder of this function will only update i.rangeKey.updated if
1633 1 : // the iterator moves into a new range key, or out of the current range
1634 1 : // key.
1635 1 : i.rangeKey.updated = i.rangeKey.hasRangeKey && !i.Valid() && i.opts.rangeKeys()
1636 1 : }
1637 1 : i.err = nil // clear cached iteration error
1638 1 : i.hasPrefix = false
1639 1 : i.batchJustRefreshed = false
1640 1 : i.lastPositioningOp = unknownLastPositionOp
1641 1 : i.requiresReposition = false
1642 1 : i.stats.ReverseSeekCount[InterfaceCall]++
1643 1 :
1644 1 : i.iterLastWithinBounds()
1645 1 : i.findPrevEntry(nil)
1646 1 : i.maybeSampleRead()
1647 1 : return i.iterValidityState == IterValid
1648 : }
1649 :
1650 : // Next moves the iterator to the next key/value pair. Returns true if the
1651 : // iterator is pointing at a valid entry and false otherwise.
1652 1 : func (i *Iterator) Next() bool {
1653 1 : return i.nextWithLimit(nil) == IterValid
1654 1 : }
1655 :
1656 : // NextWithLimit moves the iterator to the next key/value pair.
1657 : //
1658 : // If limit is provided, it serves as a best-effort exclusive limit. If the next
1659 : // key is greater than or equal to limit, the Iterator may pause and return
1660 : // IterAtLimit. Because limits are best-effort, NextWithLimit may return a key
1661 : // beyond limit.
1662 : //
1663 : // If the Iterator is configured to iterate over range keys, NextWithLimit
1664 : // guarantees it will surface any range keys with bounds overlapping the
1665 : // keyspace up to limit.
1666 1 : func (i *Iterator) NextWithLimit(limit []byte) IterValidityState {
1667 1 : return i.nextWithLimit(limit)
1668 1 : }
1669 :
1670 : // NextPrefix moves the iterator to the next key/value pair with a key
1671 : // containing a different prefix than the current key. Prefixes are determined
1672 : // by Comparer.Split. Exhausts the iterator if invoked while in prefix-iteration
1673 : // mode.
1674 : //
1675 : // It is not permitted to invoke NextPrefix while at a IterAtLimit position.
1676 : // When called in this condition, NextPrefix has non-deterministic behavior.
1677 : //
1678 : // It is not permitted to invoke NextPrefix when the Iterator has an
1679 : // upper-bound that is a versioned MVCC key (see the comment for
1680 : // Comparer.Split). It returns an error in this case.
1681 1 : func (i *Iterator) NextPrefix() bool {
1682 1 : if i.nextPrefixNotPermittedByUpperBound {
1683 1 : i.lastPositioningOp = unknownLastPositionOp
1684 1 : i.requiresReposition = false
1685 1 : i.err = errors.Errorf("NextPrefix not permitted with upper bound %s",
1686 1 : i.comparer.FormatKey(i.opts.UpperBound))
1687 1 : i.iterValidityState = IterExhausted
1688 1 : return false
1689 1 : }
1690 1 : if i.hasPrefix {
1691 1 : i.iterValidityState = IterExhausted
1692 1 : return false
1693 1 : }
1694 1 : return i.nextPrefix() == IterValid
1695 : }
1696 :
1697 1 : func (i *Iterator) nextPrefix() IterValidityState {
1698 1 : if i.rangeKey != nil {
1699 1 : // NB: Check Valid() before clearing requiresReposition.
1700 1 : i.rangeKey.prevPosHadRangeKey = i.rangeKey.hasRangeKey && i.Valid()
1701 1 : // If we have a range key but did not expose it at the previous iterator
1702 1 : // position (because the iterator was not at a valid position), updated
1703 1 : // must be true. This ensures that after an iterator op sequence like:
1704 1 : // - Next() → (IterValid, RangeBounds() = [a,b))
1705 1 : // - NextWithLimit(...) → (IterAtLimit, RangeBounds() = -)
1706 1 : // - NextWithLimit(...) → (IterValid, RangeBounds() = [a,b))
1707 1 : // the iterator returns RangeKeyChanged()=true.
1708 1 : //
1709 1 : // The remainder of this function will only update i.rangeKey.updated if
1710 1 : // the iterator moves into a new range key, or out of the current range
1711 1 : // key.
1712 1 : i.rangeKey.updated = i.rangeKey.hasRangeKey && !i.Valid() && i.opts.rangeKeys()
1713 1 : }
1714 :
1715 : // Although NextPrefix documents that behavior at IterAtLimit is undefined,
1716 : // this function handles these cases as a simple prefix-agnostic Next. This
1717 : // is done for deterministic behavior in the metamorphic tests.
1718 : //
1719 : // TODO(jackson): If the metamorphic test operation generator is adjusted to
1720 : // make generation of some operations conditional on the previous
1721 : // operations, then we can remove this behavior and explicitly error.
1722 :
1723 1 : i.lastPositioningOp = unknownLastPositionOp
1724 1 : i.requiresReposition = false
1725 1 : switch i.pos {
1726 1 : case iterPosCurForward:
1727 1 : // Positioned on the current key. Advance to the next prefix.
1728 1 : i.internalNextPrefix(i.split(i.key))
1729 0 : case iterPosCurForwardPaused:
1730 : // Positioned at a limit. Implement as a prefix-agnostic Next. See TODO
1731 : // up above. The iterator is already positioned at the next key.
1732 1 : case iterPosCurReverse:
1733 1 : // Switching directions.
1734 1 : // Unless the iterator was exhausted, reverse iteration needs to
1735 1 : // position the iterator at iterPosPrev.
1736 1 : if i.iterKey != nil {
1737 0 : i.err = errors.New("switching from reverse to forward but iter is not at prev")
1738 0 : i.iterValidityState = IterExhausted
1739 0 : return i.iterValidityState
1740 0 : }
1741 : // The Iterator is exhausted and i.iter is positioned before the first
1742 : // key. Reposition to point to the first internal key.
1743 1 : i.iterFirstWithinBounds()
1744 0 : case iterPosCurReversePaused:
1745 0 : // Positioned at a limit. Implement as a prefix-agnostic Next. See TODO
1746 0 : // up above.
1747 0 : //
1748 0 : // Switching directions; The iterator must not be exhausted since it
1749 0 : // paused.
1750 0 : if i.iterKey == nil {
1751 0 : i.err = errors.New("switching paused from reverse to forward but iter is exhausted")
1752 0 : i.iterValidityState = IterExhausted
1753 0 : return i.iterValidityState
1754 0 : }
1755 0 : i.nextUserKey()
1756 1 : case iterPosPrev:
1757 1 : // The underlying iterator is pointed to the previous key (this can
1758 1 : // only happen when switching iteration directions).
1759 1 : if i.iterKey == nil {
1760 1 : // We're positioned before the first key. Need to reposition to point to
1761 1 : // the first key.
1762 1 : i.iterFirstWithinBounds()
1763 1 : } else {
1764 1 : // Move the internal iterator back onto the user key stored in
1765 1 : // i.key. iterPosPrev guarantees that it's positioned at the last
1766 1 : // key with the user key less than i.key, so we're guaranteed to
1767 1 : // land on the correct key with a single Next.
1768 1 : i.iterKey, i.iterValue = i.iter.Next()
1769 1 : if invariants.Enabled && !i.equal(i.iterKey.UserKey, i.key) {
1770 0 : i.opts.logger.Fatalf("pebble: invariant violation: Nexting internal iterator from iterPosPrev landed on %q, not %q",
1771 0 : i.iterKey.UserKey, i.key)
1772 0 : }
1773 : }
1774 : // The internal iterator is now positioned at i.key. Advance to the next
1775 : // prefix.
1776 1 : i.internalNextPrefix(i.split(i.key))
1777 1 : case iterPosNext:
1778 1 : // Already positioned on the next key. Only call nextPrefixKey if the
1779 1 : // next key shares the same prefix.
1780 1 : if i.iterKey != nil {
1781 1 : currKeyPrefixLen := i.split(i.key)
1782 1 : iterKeyPrefixLen := i.split(i.iterKey.UserKey)
1783 1 : if bytes.Equal(i.iterKey.UserKey[:iterKeyPrefixLen], i.key[:currKeyPrefixLen]) {
1784 1 : i.internalNextPrefix(currKeyPrefixLen)
1785 1 : }
1786 : }
1787 : }
1788 :
1789 1 : i.stats.ForwardStepCount[InterfaceCall]++
1790 1 : i.findNextEntry(nil /* limit */)
1791 1 : i.maybeSampleRead()
1792 1 : return i.iterValidityState
1793 : }
1794 :
1795 1 : func (i *Iterator) internalNextPrefix(currKeyPrefixLen int) {
1796 1 : if i.iterKey == nil {
1797 1 : return
1798 1 : }
1799 : // The Next "fast-path" is not really a fast-path when there is more than
1800 : // one version. However, even with TableFormatPebblev3, there is a small
1801 : // slowdown (~10%) for one version if we remove it and only call NextPrefix.
1802 : // When there are two versions, only calling NextPrefix is ~30% faster.
1803 1 : i.stats.ForwardStepCount[InternalIterCall]++
1804 1 : if i.iterKey, i.iterValue = i.iter.Next(); i.iterKey == nil {
1805 1 : return
1806 1 : }
1807 1 : iterKeyPrefixLen := i.split(i.iterKey.UserKey)
1808 1 : if !bytes.Equal(i.iterKey.UserKey[:iterKeyPrefixLen], i.key[:currKeyPrefixLen]) {
1809 1 : return
1810 1 : }
1811 1 : i.stats.ForwardStepCount[InternalIterCall]++
1812 1 : i.prefixOrFullSeekKey = i.comparer.ImmediateSuccessor(i.prefixOrFullSeekKey[:0], i.key[:currKeyPrefixLen])
1813 1 : i.iterKey, i.iterValue = i.iter.NextPrefix(i.prefixOrFullSeekKey)
1814 1 : if invariants.Enabled && i.iterKey != nil {
1815 1 : if iterKeyPrefixLen := i.split(i.iterKey.UserKey); i.cmp(i.iterKey.UserKey[:iterKeyPrefixLen], i.prefixOrFullSeekKey) < 0 {
1816 0 : panic(errors.AssertionFailedf("pebble: iter.NextPrefix did not advance beyond the current prefix: now at %q; expected to be geq %q",
1817 0 : i.iterKey, i.prefixOrFullSeekKey))
1818 : }
1819 : }
1820 : }
1821 :
1822 1 : func (i *Iterator) nextWithLimit(limit []byte) IterValidityState {
1823 1 : i.stats.ForwardStepCount[InterfaceCall]++
1824 1 : if i.hasPrefix {
1825 1 : if limit != nil {
1826 1 : i.err = errors.New("cannot use limit with prefix iteration")
1827 1 : i.iterValidityState = IterExhausted
1828 1 : return i.iterValidityState
1829 1 : } else if i.iterValidityState == IterExhausted {
1830 1 : // No-op, already exhasuted. We avoid executing the Next because it
1831 1 : // can break invariants: Specifically, a file that fails the bloom
1832 1 : // filter test may result in its level being removed from the
1833 1 : // merging iterator. The level's removal can cause a lazy combined
1834 1 : // iterator to miss range keys and trigger a switch to combined
1835 1 : // iteration at a larger key, breaking keyspan invariants.
1836 1 : return i.iterValidityState
1837 1 : }
1838 : }
1839 1 : if i.err != nil {
1840 1 : return i.iterValidityState
1841 1 : }
1842 1 : if i.rangeKey != nil {
1843 1 : // NB: Check Valid() before clearing requiresReposition.
1844 1 : i.rangeKey.prevPosHadRangeKey = i.rangeKey.hasRangeKey && i.Valid()
1845 1 : // If we have a range key but did not expose it at the previous iterator
1846 1 : // position (because the iterator was not at a valid position), updated
1847 1 : // must be true. This ensures that after an iterator op sequence like:
1848 1 : // - Next() → (IterValid, RangeBounds() = [a,b))
1849 1 : // - NextWithLimit(...) → (IterAtLimit, RangeBounds() = -)
1850 1 : // - NextWithLimit(...) → (IterValid, RangeBounds() = [a,b))
1851 1 : // the iterator returns RangeKeyChanged()=true.
1852 1 : //
1853 1 : // The remainder of this function will only update i.rangeKey.updated if
1854 1 : // the iterator moves into a new range key, or out of the current range
1855 1 : // key.
1856 1 : i.rangeKey.updated = i.rangeKey.hasRangeKey && !i.Valid() && i.opts.rangeKeys()
1857 1 : }
1858 1 : i.lastPositioningOp = unknownLastPositionOp
1859 1 : i.requiresReposition = false
1860 1 : switch i.pos {
1861 1 : case iterPosCurForward:
1862 1 : i.nextUserKey()
1863 1 : case iterPosCurForwardPaused:
1864 : // Already at the right place.
1865 1 : case iterPosCurReverse:
1866 1 : // Switching directions.
1867 1 : // Unless the iterator was exhausted, reverse iteration needs to
1868 1 : // position the iterator at iterPosPrev.
1869 1 : if i.iterKey != nil {
1870 0 : i.err = errors.New("switching from reverse to forward but iter is not at prev")
1871 0 : i.iterValidityState = IterExhausted
1872 0 : return i.iterValidityState
1873 0 : }
1874 : // We're positioned before the first key. Need to reposition to point to
1875 : // the first key.
1876 1 : i.iterFirstWithinBounds()
1877 1 : case iterPosCurReversePaused:
1878 1 : // Switching directions.
1879 1 : // The iterator must not be exhausted since it paused.
1880 1 : if i.iterKey == nil {
1881 0 : i.err = errors.New("switching paused from reverse to forward but iter is exhausted")
1882 0 : i.iterValidityState = IterExhausted
1883 0 : return i.iterValidityState
1884 0 : }
1885 1 : i.nextUserKey()
1886 1 : case iterPosPrev:
1887 1 : // The underlying iterator is pointed to the previous key (this can
1888 1 : // only happen when switching iteration directions). We set
1889 1 : // i.iterValidityState to IterExhausted here to force the calls to
1890 1 : // nextUserKey to save the current key i.iter is pointing at in order
1891 1 : // to determine when the next user-key is reached.
1892 1 : i.iterValidityState = IterExhausted
1893 1 : if i.iterKey == nil {
1894 1 : // We're positioned before the first key. Need to reposition to point to
1895 1 : // the first key.
1896 1 : i.iterFirstWithinBounds()
1897 1 : } else {
1898 1 : i.nextUserKey()
1899 1 : }
1900 1 : i.nextUserKey()
1901 1 : case iterPosNext:
1902 : // Already at the right place.
1903 : }
1904 1 : i.findNextEntry(limit)
1905 1 : i.maybeSampleRead()
1906 1 : return i.iterValidityState
1907 : }
1908 :
1909 : // Prev moves the iterator to the previous key/value pair. Returns true if the
1910 : // iterator is pointing at a valid entry and false otherwise.
1911 1 : func (i *Iterator) Prev() bool {
1912 1 : return i.PrevWithLimit(nil) == IterValid
1913 1 : }
1914 :
1915 : // PrevWithLimit moves the iterator to the previous key/value pair.
1916 : //
1917 : // If limit is provided, it serves as a best-effort inclusive limit. If the
1918 : // previous key is less than limit, the Iterator may pause and return
1919 : // IterAtLimit. Because limits are best-effort, PrevWithLimit may return a key
1920 : // beyond limit.
1921 : //
1922 : // If the Iterator is configured to iterate over range keys, PrevWithLimit
1923 : // guarantees it will surface any range keys with bounds overlapping the
1924 : // keyspace up to limit.
1925 1 : func (i *Iterator) PrevWithLimit(limit []byte) IterValidityState {
1926 1 : i.stats.ReverseStepCount[InterfaceCall]++
1927 1 : if i.err != nil {
1928 1 : return i.iterValidityState
1929 1 : }
1930 1 : if i.rangeKey != nil {
1931 1 : // NB: Check Valid() before clearing requiresReposition.
1932 1 : i.rangeKey.prevPosHadRangeKey = i.rangeKey.hasRangeKey && i.Valid()
1933 1 : // If we have a range key but did not expose it at the previous iterator
1934 1 : // position (because the iterator was not at a valid position), updated
1935 1 : // must be true. This ensures that after an iterator op sequence like:
1936 1 : // - Next() → (IterValid, RangeBounds() = [a,b))
1937 1 : // - NextWithLimit(...) → (IterAtLimit, RangeBounds() = -)
1938 1 : // - PrevWithLimit(...) → (IterValid, RangeBounds() = [a,b))
1939 1 : // the iterator returns RangeKeyChanged()=true.
1940 1 : //
1941 1 : // The remainder of this function will only update i.rangeKey.updated if
1942 1 : // the iterator moves into a new range key, or out of the current range
1943 1 : // key.
1944 1 : i.rangeKey.updated = i.rangeKey.hasRangeKey && !i.Valid() && i.opts.rangeKeys()
1945 1 : }
1946 1 : i.lastPositioningOp = unknownLastPositionOp
1947 1 : i.requiresReposition = false
1948 1 : if i.hasPrefix {
1949 1 : i.err = errReversePrefixIteration
1950 1 : i.iterValidityState = IterExhausted
1951 1 : return i.iterValidityState
1952 1 : }
1953 1 : switch i.pos {
1954 1 : case iterPosCurForward:
1955 : // Switching directions, and will handle this below.
1956 1 : case iterPosCurForwardPaused:
1957 : // Switching directions, and will handle this below.
1958 1 : case iterPosCurReverse:
1959 1 : i.prevUserKey()
1960 1 : case iterPosCurReversePaused:
1961 : // Already at the right place.
1962 1 : case iterPosNext:
1963 : // The underlying iterator is pointed to the next key (this can only happen
1964 : // when switching iteration directions). We will handle this below.
1965 1 : case iterPosPrev:
1966 : // Already at the right place.
1967 : }
1968 1 : if i.pos == iterPosCurForward || i.pos == iterPosNext || i.pos == iterPosCurForwardPaused {
1969 1 : // Switching direction.
1970 1 : stepAgain := i.pos == iterPosNext
1971 1 :
1972 1 : // Synthetic range key markers are a special case. Consider SeekGE(b)
1973 1 : // which finds a range key [a, c). To ensure the user observes the range
1974 1 : // key, the Iterator pauses at Key() = b. The iterator must advance the
1975 1 : // internal iterator to see if there's also a coincident point key at
1976 1 : // 'b', leaving the iterator at iterPosNext if there's not.
1977 1 : //
1978 1 : // This is a problem: Synthetic range key markers are only interleaved
1979 1 : // during the original seek. A subsequent Prev() of i.iter will not move
1980 1 : // back onto the synthetic range key marker. In this case where the
1981 1 : // previous iterator position was a synthetic range key start boundary,
1982 1 : // we must not step a second time.
1983 1 : if i.isEphemeralPosition() {
1984 1 : stepAgain = false
1985 1 : }
1986 :
1987 : // We set i.iterValidityState to IterExhausted here to force the calls
1988 : // to prevUserKey to save the current key i.iter is pointing at in
1989 : // order to determine when the prev user-key is reached.
1990 1 : i.iterValidityState = IterExhausted
1991 1 : if i.iterKey == nil {
1992 1 : // We're positioned after the last key. Need to reposition to point to
1993 1 : // the last key.
1994 1 : i.iterLastWithinBounds()
1995 1 : } else {
1996 1 : i.prevUserKey()
1997 1 : }
1998 1 : if stepAgain {
1999 1 : i.prevUserKey()
2000 1 : }
2001 : }
2002 1 : i.findPrevEntry(limit)
2003 1 : i.maybeSampleRead()
2004 1 : return i.iterValidityState
2005 : }
2006 :
2007 : // iterFirstWithinBounds moves the internal iterator to the first key,
2008 : // respecting bounds.
2009 1 : func (i *Iterator) iterFirstWithinBounds() {
2010 1 : i.stats.ForwardSeekCount[InternalIterCall]++
2011 1 : if lowerBound := i.opts.GetLowerBound(); lowerBound != nil {
2012 1 : i.iterKey, i.iterValue = i.iter.SeekGE(lowerBound, base.SeekGEFlagsNone)
2013 1 : } else {
2014 1 : i.iterKey, i.iterValue = i.iter.First()
2015 1 : }
2016 : }
2017 :
2018 : // iterLastWithinBounds moves the internal iterator to the last key, respecting
2019 : // bounds.
2020 1 : func (i *Iterator) iterLastWithinBounds() {
2021 1 : i.stats.ReverseSeekCount[InternalIterCall]++
2022 1 : if upperBound := i.opts.GetUpperBound(); upperBound != nil {
2023 1 : i.iterKey, i.iterValue = i.iter.SeekLT(upperBound, base.SeekLTFlagsNone)
2024 1 : } else {
2025 1 : i.iterKey, i.iterValue = i.iter.Last()
2026 1 : }
2027 : }
2028 :
2029 : // RangeKeyData describes a range key's data, set through RangeKeySet. The key
2030 : // boundaries of the range key is provided by Iterator.RangeBounds.
2031 : type RangeKeyData struct {
2032 : Suffix []byte
2033 : Value []byte
2034 : }
2035 :
2036 : // rangeKeyWithinLimit is called during limited reverse iteration when
2037 : // positioned over a key beyond the limit. If there exists a range key that lies
2038 : // within the limit, the iterator must not pause in order to ensure the user has
2039 : // an opportunity to observe the range key within limit.
2040 : //
2041 : // It would be valid to ignore the limit whenever there's a range key covering
2042 : // the key, but that would introduce nondeterminism. To preserve determinism for
2043 : // testing, the iterator ignores the limit only if the covering range key does
2044 : // cover the keyspace within the limit.
2045 : //
2046 : // This awkwardness exists because range keys are interleaved at their inclusive
2047 : // start positions. Note that limit is inclusive.
2048 1 : func (i *Iterator) rangeKeyWithinLimit(limit []byte) bool {
2049 1 : if i.rangeKey == nil || !i.opts.rangeKeys() {
2050 1 : return false
2051 1 : }
2052 1 : s := i.rangeKey.iiter.Span()
2053 1 : // If the range key ends beyond the limit, then the range key does not cover
2054 1 : // any portion of the keyspace within the limit and it is safe to pause.
2055 1 : return s != nil && i.cmp(s.End, limit) > 0
2056 : }
2057 :
2058 : // saveRangeKey saves the current range key to the underlying iterator's current
2059 : // range key state. If the range key has not changed, saveRangeKey is a no-op.
2060 : // If there is a new range key, saveRangeKey copies all of the key, value and
2061 : // suffixes into Iterator-managed buffers.
2062 1 : func (i *Iterator) saveRangeKey() {
2063 1 : if i.rangeKey == nil || i.opts.KeyTypes == IterKeyTypePointsOnly {
2064 1 : return
2065 1 : }
2066 :
2067 1 : s := i.rangeKey.iiter.Span()
2068 1 : if s == nil {
2069 1 : i.rangeKey.hasRangeKey = false
2070 1 : i.rangeKey.updated = i.rangeKey.prevPosHadRangeKey
2071 1 : return
2072 1 : } else if !i.rangeKey.stale {
2073 1 : // The range key `s` is identical to the one currently saved. No-op.
2074 1 : return
2075 1 : }
2076 :
2077 1 : if s.KeysOrder != keyspan.BySuffixAsc {
2078 0 : panic("pebble: range key span's keys unexpectedly not in ascending suffix order")
2079 : }
2080 :
2081 : // Although `i.rangeKey.stale` is true, the span s may still be identical
2082 : // to the currently saved span. This is possible when seeking the iterator,
2083 : // which may land back on the same range key. If we previously had a range
2084 : // key and the new one has an identical start key, then it must be the same
2085 : // range key and we can avoid copying and keep `i.rangeKey.updated=false`.
2086 : //
2087 : // TODO(jackson): These key comparisons could be avoidable during relative
2088 : // positioning operations continuing in the same direction, because these
2089 : // ops will never encounter the previous position's range key while
2090 : // stale=true. However, threading whether the current op is a seek or step
2091 : // maybe isn't worth it. This key comparison is only necessary once when we
2092 : // step onto a new range key, which should be relatively rare.
2093 1 : if i.rangeKey.prevPosHadRangeKey && i.equal(i.rangeKey.start, s.Start) &&
2094 1 : i.equal(i.rangeKey.end, s.End) {
2095 1 : i.rangeKey.updated = false
2096 1 : i.rangeKey.stale = false
2097 1 : i.rangeKey.hasRangeKey = true
2098 1 : return
2099 1 : }
2100 1 : i.stats.RangeKeyStats.Count += len(s.Keys)
2101 1 : i.rangeKey.buf.Reset()
2102 1 : i.rangeKey.hasRangeKey = true
2103 1 : i.rangeKey.updated = true
2104 1 : i.rangeKey.stale = false
2105 1 : i.rangeKey.buf, i.rangeKey.start = i.rangeKey.buf.Copy(s.Start)
2106 1 : i.rangeKey.buf, i.rangeKey.end = i.rangeKey.buf.Copy(s.End)
2107 1 : i.rangeKey.keys = i.rangeKey.keys[:0]
2108 1 : for j := 0; j < len(s.Keys); j++ {
2109 1 : if invariants.Enabled {
2110 1 : if s.Keys[j].Kind() != base.InternalKeyKindRangeKeySet {
2111 0 : panic("pebble: user iteration encountered non-RangeKeySet key kind")
2112 1 : } else if j > 0 && i.cmp(s.Keys[j].Suffix, s.Keys[j-1].Suffix) < 0 {
2113 0 : panic("pebble: user iteration encountered range keys not in suffix order")
2114 : }
2115 : }
2116 1 : var rkd RangeKeyData
2117 1 : i.rangeKey.buf, rkd.Suffix = i.rangeKey.buf.Copy(s.Keys[j].Suffix)
2118 1 : i.rangeKey.buf, rkd.Value = i.rangeKey.buf.Copy(s.Keys[j].Value)
2119 1 : i.rangeKey.keys = append(i.rangeKey.keys, rkd)
2120 : }
2121 : }
2122 :
2123 : // RangeKeyChanged indicates whether the most recent iterator positioning
2124 : // operation resulted in the iterator stepping into or out of a new range key.
2125 : // If true, previously returned range key bounds and data has been invalidated.
2126 : // If false, previously obtained range key bounds, suffix and value slices are
2127 : // still valid and may continue to be read.
2128 : //
2129 : // Invalid iterator positions are considered to not hold range keys, meaning
2130 : // that if an iterator steps from an IterExhausted or IterAtLimit position onto
2131 : // a position with a range key, RangeKeyChanged will yield true.
2132 1 : func (i *Iterator) RangeKeyChanged() bool {
2133 1 : return i.iterValidityState == IterValid && i.rangeKey != nil && i.rangeKey.updated
2134 1 : }
2135 :
2136 : // HasPointAndRange indicates whether there exists a point key, a range key or
2137 : // both at the current iterator position.
2138 1 : func (i *Iterator) HasPointAndRange() (hasPoint, hasRange bool) {
2139 1 : if i.iterValidityState != IterValid || i.requiresReposition {
2140 1 : return false, false
2141 1 : }
2142 1 : if i.opts.KeyTypes == IterKeyTypePointsOnly {
2143 1 : return true, false
2144 1 : }
2145 1 : return i.rangeKey == nil || !i.rangeKey.rangeKeyOnly, i.rangeKey != nil && i.rangeKey.hasRangeKey
2146 : }
2147 :
2148 : // RangeBounds returns the start (inclusive) and end (exclusive) bounds of the
2149 : // range key covering the current iterator position. RangeBounds returns nil
2150 : // bounds if there is no range key covering the current iterator position, or
2151 : // the iterator is not configured to surface range keys.
2152 : //
2153 : // If valid, the returned start bound is less than or equal to Key() and the
2154 : // returned end bound is greater than Key().
2155 1 : func (i *Iterator) RangeBounds() (start, end []byte) {
2156 1 : if i.rangeKey == nil || !i.opts.rangeKeys() || !i.rangeKey.hasRangeKey {
2157 0 : return nil, nil
2158 0 : }
2159 1 : return i.rangeKey.start, i.rangeKey.end
2160 : }
2161 :
2162 : // Key returns the key of the current key/value pair, or nil if done. The
2163 : // caller should not modify the contents of the returned slice, and its
2164 : // contents may change on the next call to Next.
2165 : //
2166 : // If positioned at an iterator position that only holds a range key, Key()
2167 : // always returns the start bound of the range key. Otherwise, it returns the
2168 : // point key's key.
2169 1 : func (i *Iterator) Key() []byte {
2170 1 : return i.key
2171 1 : }
2172 :
2173 : // Value returns the value of the current key/value pair, or nil if done. The
2174 : // caller should not modify the contents of the returned slice, and its
2175 : // contents may change on the next call to Next.
2176 : //
2177 : // Only valid if HasPointAndRange() returns true for hasPoint.
2178 : // Deprecated: use ValueAndErr instead.
2179 1 : func (i *Iterator) Value() []byte {
2180 1 : val, _ := i.ValueAndErr()
2181 1 : return val
2182 1 : }
2183 :
2184 : // ValueAndErr returns the value, and any error encountered in extracting the value.
2185 : // REQUIRES: i.Error()==nil and HasPointAndRange() returns true for hasPoint.
2186 : //
2187 : // The caller should not modify the contents of the returned slice, and its
2188 : // contents may change on the next call to Next.
2189 1 : func (i *Iterator) ValueAndErr() ([]byte, error) {
2190 1 : val, callerOwned, err := i.value.Value(i.lazyValueBuf)
2191 1 : if err != nil {
2192 0 : i.err = err
2193 0 : }
2194 1 : if callerOwned {
2195 1 : i.lazyValueBuf = val[:0]
2196 1 : }
2197 1 : return val, err
2198 : }
2199 :
2200 : // LazyValue returns the LazyValue. Only for advanced use cases.
2201 : // REQUIRES: i.Error()==nil and HasPointAndRange() returns true for hasPoint.
2202 0 : func (i *Iterator) LazyValue() LazyValue {
2203 0 : return i.value
2204 0 : }
2205 :
2206 : // RangeKeys returns the range key values and their suffixes covering the
2207 : // current iterator position. The range bounds may be retrieved separately
2208 : // through Iterator.RangeBounds().
2209 1 : func (i *Iterator) RangeKeys() []RangeKeyData {
2210 1 : if i.rangeKey == nil || !i.opts.rangeKeys() || !i.rangeKey.hasRangeKey {
2211 0 : return nil
2212 0 : }
2213 1 : return i.rangeKey.keys
2214 : }
2215 :
2216 : // Valid returns true if the iterator is positioned at a valid key/value pair
2217 : // and false otherwise.
2218 1 : func (i *Iterator) Valid() bool {
2219 1 : valid := i.iterValidityState == IterValid && !i.requiresReposition
2220 1 : if invariants.Enabled {
2221 1 : if err := i.Error(); valid && err != nil {
2222 0 : panic(errors.WithSecondaryError(errors.AssertionFailedf("pebble: iterator is valid with non-nil Error"), err))
2223 : }
2224 : }
2225 1 : return valid
2226 : }
2227 :
2228 : // Error returns any accumulated error.
2229 1 : func (i *Iterator) Error() error {
2230 1 : if i.iter != nil {
2231 1 : return firstError(i.err, i.iter.Error())
2232 1 : }
2233 0 : return i.err
2234 : }
2235 :
2236 : const maxKeyBufCacheSize = 4 << 10 // 4 KB
2237 :
2238 : // Close closes the iterator and returns any accumulated error. Exhausting
2239 : // all the key/value pairs in a table is not considered to be an error.
2240 : // It is not valid to call any method, including Close, after the iterator
2241 : // has been closed.
2242 1 : func (i *Iterator) Close() error {
2243 1 : // Close the child iterator before releasing the readState because when the
2244 1 : // readState is released sstables referenced by the readState may be deleted
2245 1 : // which will fail on Windows if the sstables are still open by the child
2246 1 : // iterator.
2247 1 : if i.iter != nil {
2248 1 : i.err = firstError(i.err, i.iter.Close())
2249 1 :
2250 1 : // Closing i.iter did not necessarily close the point and range key
2251 1 : // iterators. Calls to SetOptions may have 'disconnected' either one
2252 1 : // from i.iter if iteration key types were changed. Both point and range
2253 1 : // key iterators are preserved in case the iterator needs to switch key
2254 1 : // types again. We explicitly close both of these iterators here.
2255 1 : //
2256 1 : // NB: If the iterators were still connected to i.iter, they may be
2257 1 : // closed, but calling Close on a closed internal iterator or fragment
2258 1 : // iterator is allowed.
2259 1 : if i.pointIter != nil && !i.closePointIterOnce {
2260 1 : i.err = firstError(i.err, i.pointIter.Close())
2261 1 : }
2262 1 : if i.rangeKey != nil && i.rangeKey.rangeKeyIter != nil {
2263 1 : i.err = firstError(i.err, i.rangeKey.rangeKeyIter.Close())
2264 1 : }
2265 : }
2266 1 : err := i.err
2267 1 :
2268 1 : if i.readState != nil {
2269 1 : if i.readSampling.pendingCompactions.size > 0 {
2270 1 : // Copy pending read compactions using db.mu.Lock()
2271 1 : i.readState.db.mu.Lock()
2272 1 : i.readState.db.mu.compact.readCompactions.combine(&i.readSampling.pendingCompactions, i.cmp)
2273 1 : reschedule := i.readState.db.mu.compact.rescheduleReadCompaction
2274 1 : i.readState.db.mu.compact.rescheduleReadCompaction = false
2275 1 : concurrentCompactions := i.readState.db.mu.compact.compactingCount
2276 1 : i.readState.db.mu.Unlock()
2277 1 :
2278 1 : if reschedule && concurrentCompactions == 0 {
2279 0 : // In a read heavy workload, flushes may not happen frequently enough to
2280 0 : // schedule compactions.
2281 0 : i.readState.db.compactionSchedulers.Add(1)
2282 0 : go i.readState.db.maybeScheduleCompactionAsync()
2283 0 : }
2284 : }
2285 :
2286 1 : i.readState.unref()
2287 1 : i.readState = nil
2288 : }
2289 :
2290 1 : if i.version != nil {
2291 1 : i.version.Unref()
2292 1 : }
2293 :
2294 1 : for _, readers := range i.externalReaders {
2295 1 : for _, r := range readers {
2296 1 : err = firstError(err, r.Close())
2297 1 : }
2298 : }
2299 :
2300 : // Close the closer for the current value if one was open.
2301 1 : if i.valueCloser != nil {
2302 1 : err = firstError(err, i.valueCloser.Close())
2303 1 : i.valueCloser = nil
2304 1 : }
2305 :
2306 1 : if i.rangeKey != nil {
2307 1 :
2308 1 : i.rangeKey.rangeKeyBuffers.PrepareForReuse()
2309 1 : *i.rangeKey = iteratorRangeKeyState{
2310 1 : rangeKeyBuffers: i.rangeKey.rangeKeyBuffers,
2311 1 : }
2312 1 : iterRangeKeyStateAllocPool.Put(i.rangeKey)
2313 1 : i.rangeKey = nil
2314 1 : }
2315 1 : if alloc := i.alloc; alloc != nil {
2316 1 : // Avoid caching the key buf if it is overly large. The constant is fairly
2317 1 : // arbitrary.
2318 1 : if cap(i.keyBuf) >= maxKeyBufCacheSize {
2319 0 : alloc.keyBuf = nil
2320 1 : } else {
2321 1 : alloc.keyBuf = i.keyBuf
2322 1 : }
2323 1 : if cap(i.prefixOrFullSeekKey) >= maxKeyBufCacheSize {
2324 0 : alloc.prefixOrFullSeekKey = nil
2325 1 : } else {
2326 1 : alloc.prefixOrFullSeekKey = i.prefixOrFullSeekKey
2327 1 : }
2328 1 : for j := range i.boundsBuf {
2329 1 : if cap(i.boundsBuf[j]) >= maxKeyBufCacheSize {
2330 0 : alloc.boundsBuf[j] = nil
2331 1 : } else {
2332 1 : alloc.boundsBuf[j] = i.boundsBuf[j]
2333 1 : }
2334 : }
2335 1 : *alloc = iterAlloc{
2336 1 : keyBuf: alloc.keyBuf,
2337 1 : boundsBuf: alloc.boundsBuf,
2338 1 : prefixOrFullSeekKey: alloc.prefixOrFullSeekKey,
2339 1 : }
2340 1 : iterAllocPool.Put(alloc)
2341 1 : } else if alloc := i.getIterAlloc; alloc != nil {
2342 1 : if cap(i.keyBuf) >= maxKeyBufCacheSize {
2343 0 : alloc.keyBuf = nil
2344 1 : } else {
2345 1 : alloc.keyBuf = i.keyBuf
2346 1 : }
2347 1 : *alloc = getIterAlloc{
2348 1 : keyBuf: alloc.keyBuf,
2349 1 : }
2350 1 : getIterAllocPool.Put(alloc)
2351 : }
2352 1 : return err
2353 : }
2354 :
2355 : // SetBounds sets the lower and upper bounds for the iterator. Once SetBounds
2356 : // returns, the caller is free to mutate the provided slices.
2357 : //
2358 : // The iterator will always be invalidated and must be repositioned with a call
2359 : // to SeekGE, SeekPrefixGE, SeekLT, First, or Last.
2360 1 : func (i *Iterator) SetBounds(lower, upper []byte) {
2361 1 : // Ensure that the Iterator appears exhausted, regardless of whether we
2362 1 : // actually have to invalidate the internal iterator. Optimizations that
2363 1 : // avoid exhaustion are an internal implementation detail that shouldn't
2364 1 : // leak through the interface. The caller should still call an absolute
2365 1 : // positioning method to reposition the iterator.
2366 1 : i.requiresReposition = true
2367 1 :
2368 1 : if ((i.opts.LowerBound == nil) == (lower == nil)) &&
2369 1 : ((i.opts.UpperBound == nil) == (upper == nil)) &&
2370 1 : i.equal(i.opts.LowerBound, lower) &&
2371 1 : i.equal(i.opts.UpperBound, upper) {
2372 1 : // Unchanged, noop.
2373 1 : return
2374 1 : }
2375 :
2376 : // Copy the user-provided bounds into an Iterator-owned buffer, and set them
2377 : // on i.opts.{Lower,Upper}Bound.
2378 1 : i.processBounds(lower, upper)
2379 1 :
2380 1 : i.iter.SetBounds(i.opts.LowerBound, i.opts.UpperBound)
2381 1 : // If the iterator has an open point iterator that's not currently being
2382 1 : // used, propagate the new bounds to it.
2383 1 : if i.pointIter != nil && !i.opts.pointKeys() {
2384 1 : i.pointIter.SetBounds(i.opts.LowerBound, i.opts.UpperBound)
2385 1 : }
2386 : // If the iterator has a range key iterator, propagate bounds to it. The
2387 : // top-level SetBounds on the interleaving iterator (i.iter) won't propagate
2388 : // bounds to the range key iterator stack, because the FragmentIterator
2389 : // interface doesn't define a SetBounds method. We need to directly inform
2390 : // the iterConfig stack.
2391 1 : if i.rangeKey != nil {
2392 1 : i.rangeKey.iterConfig.SetBounds(i.opts.LowerBound, i.opts.UpperBound)
2393 1 : }
2394 :
2395 : // Even though this is not a positioning operation, the alteration of the
2396 : // bounds means we cannot optimize Seeks by using Next.
2397 1 : i.invalidate()
2398 : }
2399 :
2400 : // SetContext replaces the context provided at iterator creation, or the last
2401 : // one provided by SetContext. Even though iterators are expected to be
2402 : // short-lived, there are some cases where either (a) iterators are used far
2403 : // from the code that created them, (b) iterators are reused (while being
2404 : // short-lived) for processing different requests. For such scenarios, we
2405 : // allow the caller to replace the context.
2406 0 : func (i *Iterator) SetContext(ctx context.Context) {
2407 0 : i.ctx = ctx
2408 0 : i.iter.SetContext(ctx)
2409 0 : // If the iterator has an open point iterator that's not currently being
2410 0 : // used, propagate the new context to it.
2411 0 : if i.pointIter != nil && !i.opts.pointKeys() {
2412 0 : i.pointIter.SetContext(i.ctx)
2413 0 : }
2414 : }
2415 :
2416 : // Initialization and changing of the bounds must call processBounds.
2417 : // processBounds saves the bounds and computes derived state from those
2418 : // bounds.
2419 1 : func (i *Iterator) processBounds(lower, upper []byte) {
2420 1 : // Copy the user-provided bounds into an Iterator-owned buffer. We can't
2421 1 : // overwrite the current bounds, because some internal iterators compare old
2422 1 : // and new bounds for optimizations.
2423 1 :
2424 1 : buf := i.boundsBuf[i.boundsBufIdx][:0]
2425 1 : if lower != nil {
2426 1 : buf = append(buf, lower...)
2427 1 : i.opts.LowerBound = buf
2428 1 : } else {
2429 1 : i.opts.LowerBound = nil
2430 1 : }
2431 1 : i.nextPrefixNotPermittedByUpperBound = false
2432 1 : if upper != nil {
2433 1 : buf = append(buf, upper...)
2434 1 : i.opts.UpperBound = buf[len(buf)-len(upper):]
2435 1 : if i.comparer.Split != nil {
2436 1 : if i.comparer.Split(i.opts.UpperBound) != len(i.opts.UpperBound) {
2437 1 : // Setting an upper bound that is a versioned MVCC key. This means
2438 1 : // that a key can have some MVCC versions before the upper bound and
2439 1 : // some after. This causes significant complications for NextPrefix,
2440 1 : // so we bar the user of NextPrefix.
2441 1 : i.nextPrefixNotPermittedByUpperBound = true
2442 1 : }
2443 : }
2444 1 : } else {
2445 1 : i.opts.UpperBound = nil
2446 1 : }
2447 1 : i.boundsBuf[i.boundsBufIdx] = buf
2448 1 : i.boundsBufIdx = 1 - i.boundsBufIdx
2449 : }
2450 :
2451 : // SetOptions sets new iterator options for the iterator. Note that the lower
2452 : // and upper bounds applied here will supersede any bounds set by previous calls
2453 : // to SetBounds.
2454 : //
2455 : // Note that the slices provided in this SetOptions must not be changed by the
2456 : // caller until the iterator is closed, or a subsequent SetBounds or SetOptions
2457 : // has returned. This is because comparisons between the existing and new bounds
2458 : // are sometimes used to optimize seeking. See the extended commentary on
2459 : // SetBounds.
2460 : //
2461 : // If the iterator was created over an indexed mutable batch, the iterator's
2462 : // view of the mutable batch is refreshed.
2463 : //
2464 : // The iterator will always be invalidated and must be repositioned with a call
2465 : // to SeekGE, SeekPrefixGE, SeekLT, First, or Last.
2466 : //
2467 : // If only lower and upper bounds need to be modified, prefer SetBounds.
2468 1 : func (i *Iterator) SetOptions(o *IterOptions) {
2469 1 : if i.externalReaders != nil {
2470 1 : if err := validateExternalIterOpts(o); err != nil {
2471 0 : panic(err)
2472 : }
2473 : }
2474 :
2475 : // Ensure that the Iterator appears exhausted, regardless of whether we
2476 : // actually have to invalidate the internal iterator. Optimizations that
2477 : // avoid exhaustion are an internal implementation detail that shouldn't
2478 : // leak through the interface. The caller should still call an absolute
2479 : // positioning method to reposition the iterator.
2480 1 : i.requiresReposition = true
2481 1 :
2482 1 : // Check if global state requires we close all internal iterators.
2483 1 : //
2484 1 : // If the Iterator is in an error state, invalidate the existing iterators
2485 1 : // so that we reconstruct an iterator state from scratch.
2486 1 : //
2487 1 : // If OnlyReadGuaranteedDurable changed, the iterator stacks are incorrect,
2488 1 : // improperly including or excluding memtables. Invalidate them so that
2489 1 : // finishInitializingIter will reconstruct them.
2490 1 : //
2491 1 : // If either the original options or the new options specify a table filter,
2492 1 : // we need to reconstruct the iterator stacks. If they both supply a table
2493 1 : // filter, we can't be certain that it's the same filter since we have no
2494 1 : // mechanism to compare the filter closures.
2495 1 : closeBoth := i.err != nil ||
2496 1 : o.OnlyReadGuaranteedDurable != i.opts.OnlyReadGuaranteedDurable ||
2497 1 : o.TableFilter != nil || i.opts.TableFilter != nil
2498 1 :
2499 1 : // If either options specify block property filters for an iterator stack,
2500 1 : // reconstruct it.
2501 1 : if i.pointIter != nil && (closeBoth || len(o.PointKeyFilters) > 0 || len(i.opts.PointKeyFilters) > 0 ||
2502 1 : o.RangeKeyMasking.Filter != nil || i.opts.RangeKeyMasking.Filter != nil || o.SkipPoint != nil ||
2503 1 : i.opts.SkipPoint != nil) {
2504 1 : i.err = firstError(i.err, i.pointIter.Close())
2505 1 : i.pointIter = nil
2506 1 : }
2507 1 : if i.rangeKey != nil {
2508 1 : if closeBoth || len(o.RangeKeyFilters) > 0 || len(i.opts.RangeKeyFilters) > 0 {
2509 1 : i.err = firstError(i.err, i.rangeKey.rangeKeyIter.Close())
2510 1 : i.rangeKey = nil
2511 1 : } else {
2512 1 : // If there's still a range key iterator stack, invalidate the
2513 1 : // iterator. This ensures RangeKeyChanged() returns true if a
2514 1 : // subsequent positioning operation discovers a range key. It also
2515 1 : // prevents seek no-op optimizations.
2516 1 : i.invalidate()
2517 1 : }
2518 : }
2519 :
2520 : // If the iterator is backed by a batch that's been mutated, refresh its
2521 : // existing point and range-key iterators, and invalidate the iterator to
2522 : // prevent seek-using-next optimizations. If we don't yet have a point-key
2523 : // iterator or range-key iterator but we require one, it'll be created in
2524 : // the slow path that reconstructs the iterator in finishInitializingIter.
2525 1 : if i.batch != nil {
2526 1 : nextBatchSeqNum := (uint64(len(i.batch.data)) | base.InternalKeySeqNumBatch)
2527 1 : if nextBatchSeqNum != i.batchSeqNum {
2528 1 : i.batchSeqNum = nextBatchSeqNum
2529 1 : if i.merging != nil {
2530 1 : i.merging.batchSnapshot = nextBatchSeqNum
2531 1 : }
2532 : // Prevent a no-op seek optimization on the next seek. We won't be
2533 : // able to reuse the top-level Iterator state, because it may be
2534 : // incorrect after the inclusion of new batch mutations.
2535 1 : i.batchJustRefreshed = true
2536 1 : if i.pointIter != nil && i.batch.countRangeDels > 0 {
2537 1 : if i.batchRangeDelIter.Count() == 0 {
2538 1 : // When we constructed this iterator, there were no
2539 1 : // rangedels in the batch. Iterator construction will
2540 1 : // have excluded the batch rangedel iterator from the
2541 1 : // point iterator stack. We need to reconstruct the
2542 1 : // point iterator to add i.batchRangeDelIter into the
2543 1 : // iterator stack.
2544 1 : i.err = firstError(i.err, i.pointIter.Close())
2545 1 : i.pointIter = nil
2546 1 : } else {
2547 1 : // There are range deletions in the batch and we already
2548 1 : // have a batch rangedel iterator. We can update the
2549 1 : // batch rangedel iterator in place.
2550 1 : //
2551 1 : // NB: There may or may not be new range deletions. We
2552 1 : // can't tell based on i.batchRangeDelIter.Count(),
2553 1 : // which is the count of fragmented range deletions, NOT
2554 1 : // the number of range deletions written to the batch
2555 1 : // [i.batch.countRangeDels].
2556 1 : i.batch.initRangeDelIter(&i.opts, &i.batchRangeDelIter, nextBatchSeqNum)
2557 1 : }
2558 : }
2559 1 : if i.rangeKey != nil && i.batch.countRangeKeys > 0 {
2560 1 : if i.batchRangeKeyIter.Count() == 0 {
2561 1 : // When we constructed this iterator, there were no range
2562 1 : // keys in the batch. Iterator construction will have
2563 1 : // excluded the batch rangekey iterator from the range key
2564 1 : // iterator stack. We need to reconstruct the range key
2565 1 : // iterator to add i.batchRangeKeyIter into the iterator
2566 1 : // stack.
2567 1 : i.err = firstError(i.err, i.rangeKey.rangeKeyIter.Close())
2568 1 : i.rangeKey = nil
2569 1 : } else {
2570 1 : // There are range keys in the batch and we already
2571 1 : // have a batch rangekey iterator. We can update the batch
2572 1 : // rangekey iterator in place.
2573 1 : //
2574 1 : // NB: There may or may not be new range keys. We can't
2575 1 : // tell based on i.batchRangeKeyIter.Count(), which is the
2576 1 : // count of fragmented range keys, NOT the number of
2577 1 : // range keys written to the batch [i.batch.countRangeKeys].
2578 1 : i.batch.initRangeKeyIter(&i.opts, &i.batchRangeKeyIter, nextBatchSeqNum)
2579 1 : i.invalidate()
2580 1 : }
2581 : }
2582 : }
2583 : }
2584 :
2585 : // Reset combinedIterState.initialized in case the iterator key types
2586 : // changed. If there's already a range key iterator stack, the combined
2587 : // iterator is already initialized. Additionally, if the iterator is not
2588 : // configured to include range keys, mark it as initialized to signal that
2589 : // lower level iterators should not trigger a switch to combined iteration.
2590 1 : i.lazyCombinedIter.combinedIterState = combinedIterState{
2591 1 : initialized: i.rangeKey != nil || !i.opts.rangeKeys(),
2592 1 : }
2593 1 :
2594 1 : boundsEqual := ((i.opts.LowerBound == nil) == (o.LowerBound == nil)) &&
2595 1 : ((i.opts.UpperBound == nil) == (o.UpperBound == nil)) &&
2596 1 : i.equal(i.opts.LowerBound, o.LowerBound) &&
2597 1 : i.equal(i.opts.UpperBound, o.UpperBound)
2598 1 :
2599 1 : if boundsEqual && o.KeyTypes == i.opts.KeyTypes &&
2600 1 : (i.pointIter != nil || !i.opts.pointKeys()) &&
2601 1 : (i.rangeKey != nil || !i.opts.rangeKeys() || i.opts.KeyTypes == IterKeyTypePointsAndRanges) &&
2602 1 : i.equal(o.RangeKeyMasking.Suffix, i.opts.RangeKeyMasking.Suffix) &&
2603 1 : o.UseL6Filters == i.opts.UseL6Filters {
2604 1 : // The options are identical, so we can likely use the fast path. In
2605 1 : // addition to all the above constraints, we cannot use the fast path if
2606 1 : // configured to perform lazy combined iteration but an indexed batch
2607 1 : // used by the iterator now contains range keys. Lazy combined iteration
2608 1 : // is not compatible with batch range keys because we always need to
2609 1 : // merge the batch's range keys into iteration.
2610 1 : if i.rangeKey != nil || !i.opts.rangeKeys() || i.batch == nil || i.batch.countRangeKeys == 0 {
2611 1 : // Fast path. This preserves the Seek-using-Next optimizations as
2612 1 : // long as the iterator wasn't already invalidated up above.
2613 1 : return
2614 1 : }
2615 : }
2616 : // Slow path.
2617 :
2618 : // The options changed. Save the new ones to i.opts.
2619 1 : if boundsEqual {
2620 1 : // Copying the options into i.opts will overwrite LowerBound and
2621 1 : // UpperBound fields with the user-provided slices. We need to hold on
2622 1 : // to the Pebble-owned slices, so save them and re-set them after the
2623 1 : // copy.
2624 1 : lower, upper := i.opts.LowerBound, i.opts.UpperBound
2625 1 : i.opts = *o
2626 1 : i.opts.LowerBound, i.opts.UpperBound = lower, upper
2627 1 : } else {
2628 1 : i.opts = *o
2629 1 : i.processBounds(o.LowerBound, o.UpperBound)
2630 1 : // Propagate the changed bounds to the existing point iterator.
2631 1 : // NB: We propagate i.opts.{Lower,Upper}Bound, not o.{Lower,Upper}Bound
2632 1 : // because i.opts now point to buffers owned by Pebble.
2633 1 : if i.pointIter != nil {
2634 1 : i.pointIter.SetBounds(i.opts.LowerBound, i.opts.UpperBound)
2635 1 : }
2636 1 : if i.rangeKey != nil {
2637 1 : i.rangeKey.iterConfig.SetBounds(i.opts.LowerBound, i.opts.UpperBound)
2638 1 : }
2639 : }
2640 :
2641 : // Even though this is not a positioning operation, the invalidation of the
2642 : // iterator stack means we cannot optimize Seeks by using Next.
2643 1 : i.invalidate()
2644 1 :
2645 1 : // Iterators created through NewExternalIter have a different iterator
2646 1 : // initialization process.
2647 1 : if i.externalReaders != nil {
2648 1 : finishInitializingExternal(i.ctx, i)
2649 1 : return
2650 1 : }
2651 1 : finishInitializingIter(i.ctx, i.alloc)
2652 : }
2653 :
2654 1 : func (i *Iterator) invalidate() {
2655 1 : i.lastPositioningOp = invalidatedLastPositionOp
2656 1 : i.hasPrefix = false
2657 1 : i.iterKey = nil
2658 1 : i.iterValue = LazyValue{}
2659 1 : i.err = nil
2660 1 : // This switch statement isn't necessary for correctness since callers
2661 1 : // should call a repositioning method. We could have arbitrarily set i.pos
2662 1 : // to one of the values. But it results in more intuitive behavior in
2663 1 : // tests, which do not always reposition.
2664 1 : switch i.pos {
2665 1 : case iterPosCurForward, iterPosNext, iterPosCurForwardPaused:
2666 1 : i.pos = iterPosCurForward
2667 1 : case iterPosCurReverse, iterPosPrev, iterPosCurReversePaused:
2668 1 : i.pos = iterPosCurReverse
2669 : }
2670 1 : i.iterValidityState = IterExhausted
2671 1 : if i.rangeKey != nil {
2672 1 : i.rangeKey.iiter.Invalidate()
2673 1 : i.rangeKey.prevPosHadRangeKey = false
2674 1 : }
2675 : }
2676 :
2677 : // Metrics returns per-iterator metrics.
2678 0 : func (i *Iterator) Metrics() IteratorMetrics {
2679 0 : m := IteratorMetrics{
2680 0 : ReadAmp: 1,
2681 0 : }
2682 0 : if mi, ok := i.iter.(*mergingIter); ok {
2683 0 : m.ReadAmp = len(mi.levels)
2684 0 : }
2685 0 : return m
2686 : }
2687 :
2688 : // ResetStats resets the stats to 0.
2689 0 : func (i *Iterator) ResetStats() {
2690 0 : i.stats = IteratorStats{}
2691 0 : }
2692 :
2693 : // Stats returns the current stats.
2694 1 : func (i *Iterator) Stats() IteratorStats {
2695 1 : return i.stats
2696 1 : }
2697 :
2698 : // CloneOptions configures an iterator constructed through Iterator.Clone.
2699 : type CloneOptions struct {
2700 : // IterOptions, if non-nil, define the iterator options to configure a
2701 : // cloned iterator. If nil, the clone adopts the same IterOptions as the
2702 : // iterator being cloned.
2703 : IterOptions *IterOptions
2704 : // RefreshBatchView may be set to true when cloning an Iterator over an
2705 : // indexed batch. When false, the clone adopts the same (possibly stale)
2706 : // view of the indexed batch as the cloned Iterator. When true, the clone is
2707 : // constructed with a refreshed view of the batch, observing all of the
2708 : // batch's mutations at the time of the Clone. If the cloned iterator was
2709 : // not constructed to read over an indexed batch, RefreshVatchView has no
2710 : // effect.
2711 : RefreshBatchView bool
2712 : }
2713 :
2714 : // Clone creates a new Iterator over the same underlying data, i.e., over the
2715 : // same {batch, memtables, sstables}). The resulting iterator is not positioned.
2716 : // It starts with the same IterOptions, unless opts.IterOptions is set.
2717 : //
2718 : // When called on an Iterator over an indexed batch, the clone's visibility of
2719 : // the indexed batch is determined by CloneOptions.RefreshBatchView. If false,
2720 : // the clone inherits the iterator's current (possibly stale) view of the batch,
2721 : // and callers may call SetOptions to subsequently refresh the clone's view to
2722 : // include all batch mutations. If true, the clone is constructed with a
2723 : // complete view of the indexed batch's mutations at the time of the Clone.
2724 : //
2725 : // Callers can use Clone if they need multiple iterators that need to see
2726 : // exactly the same underlying state of the DB. This should not be used to
2727 : // extend the lifetime of the data backing the original Iterator since that
2728 : // will cause an increase in memory and disk usage (use NewSnapshot for that
2729 : // purpose).
2730 1 : func (i *Iterator) Clone(opts CloneOptions) (*Iterator, error) {
2731 1 : return i.CloneWithContext(context.Background(), opts)
2732 1 : }
2733 :
2734 : // CloneWithContext is like Clone, and additionally accepts a context for
2735 : // tracing.
2736 1 : func (i *Iterator) CloneWithContext(ctx context.Context, opts CloneOptions) (*Iterator, error) {
2737 1 : if opts.IterOptions == nil {
2738 1 : opts.IterOptions = &i.opts
2739 1 : }
2740 1 : if i.batchOnlyIter {
2741 1 : return nil, errors.Errorf("cannot Clone a batch-only Iterator")
2742 1 : }
2743 1 : readState := i.readState
2744 1 : vers := i.version
2745 1 : if readState == nil && vers == nil {
2746 1 : return nil, errors.Errorf("cannot Clone a closed Iterator")
2747 1 : }
2748 : // i is already holding a ref, so there is no race with unref here.
2749 : //
2750 : // TODO(bilal): If the underlying iterator was created on a snapshot, we could
2751 : // grab a reference to the current readState instead of reffing the original
2752 : // readState. This allows us to release references to some zombie sstables
2753 : // and memtables.
2754 1 : if readState != nil {
2755 1 : readState.ref()
2756 1 : }
2757 1 : if vers != nil {
2758 1 : vers.Ref()
2759 1 : }
2760 : // Bundle various structures under a single umbrella in order to allocate
2761 : // them together.
2762 1 : buf := iterAllocPool.Get().(*iterAlloc)
2763 1 : dbi := &buf.dbi
2764 1 : *dbi = Iterator{
2765 1 : ctx: ctx,
2766 1 : opts: *opts.IterOptions,
2767 1 : alloc: buf,
2768 1 : merge: i.merge,
2769 1 : comparer: i.comparer,
2770 1 : readState: readState,
2771 1 : version: vers,
2772 1 : keyBuf: buf.keyBuf,
2773 1 : prefixOrFullSeekKey: buf.prefixOrFullSeekKey,
2774 1 : boundsBuf: buf.boundsBuf,
2775 1 : batch: i.batch,
2776 1 : batchSeqNum: i.batchSeqNum,
2777 1 : newIters: i.newIters,
2778 1 : newIterRangeKey: i.newIterRangeKey,
2779 1 : seqNum: i.seqNum,
2780 1 : }
2781 1 : dbi.processBounds(dbi.opts.LowerBound, dbi.opts.UpperBound)
2782 1 :
2783 1 : // If the caller requested the clone have a current view of the indexed
2784 1 : // batch, set the clone's batch sequence number appropriately.
2785 1 : if i.batch != nil && opts.RefreshBatchView {
2786 1 : dbi.batchSeqNum = (uint64(len(i.batch.data)) | base.InternalKeySeqNumBatch)
2787 1 : }
2788 :
2789 1 : return finishInitializingIter(ctx, buf), nil
2790 : }
2791 :
2792 : // Merge adds all of the argument's statistics to the receiver. It may be used
2793 : // to accumulate stats across multiple iterators.
2794 1 : func (stats *IteratorStats) Merge(o IteratorStats) {
2795 1 : for i := InterfaceCall; i < NumStatsKind; i++ {
2796 1 : stats.ForwardSeekCount[i] += o.ForwardSeekCount[i]
2797 1 : stats.ReverseSeekCount[i] += o.ReverseSeekCount[i]
2798 1 : stats.ForwardStepCount[i] += o.ForwardStepCount[i]
2799 1 : stats.ReverseStepCount[i] += o.ReverseStepCount[i]
2800 1 : }
2801 1 : stats.InternalStats.Merge(o.InternalStats)
2802 1 : stats.RangeKeyStats.Merge(o.RangeKeyStats)
2803 : }
2804 :
2805 1 : func (stats *IteratorStats) String() string {
2806 1 : return redact.StringWithoutMarkers(stats)
2807 1 : }
2808 :
2809 : // SafeFormat implements the redact.SafeFormatter interface.
2810 1 : func (stats *IteratorStats) SafeFormat(s redact.SafePrinter, verb rune) {
2811 1 : for i := range stats.ForwardStepCount {
2812 1 : switch IteratorStatsKind(i) {
2813 1 : case InterfaceCall:
2814 1 : s.SafeString("(interface (dir, seek, step): ")
2815 1 : case InternalIterCall:
2816 1 : s.SafeString(", (internal (dir, seek, step): ")
2817 : }
2818 1 : s.Printf("(fwd, %d, %d), (rev, %d, %d))",
2819 1 : redact.Safe(stats.ForwardSeekCount[i]), redact.Safe(stats.ForwardStepCount[i]),
2820 1 : redact.Safe(stats.ReverseSeekCount[i]), redact.Safe(stats.ReverseStepCount[i]))
2821 : }
2822 1 : if stats.InternalStats != (InternalIteratorStats{}) {
2823 1 : s.SafeString(",\n(internal-stats: ")
2824 1 : s.Printf("(block-bytes: (total %s, cached %s, read-time %s)), "+
2825 1 : "(points: (count %s, key-bytes %s, value-bytes %s, tombstoned %s))",
2826 1 : humanize.Bytes.Uint64(stats.InternalStats.BlockBytes),
2827 1 : humanize.Bytes.Uint64(stats.InternalStats.BlockBytesInCache),
2828 1 : humanize.FormattedString(stats.InternalStats.BlockReadDuration.String()),
2829 1 : humanize.Count.Uint64(stats.InternalStats.PointCount),
2830 1 : humanize.Bytes.Uint64(stats.InternalStats.KeyBytes),
2831 1 : humanize.Bytes.Uint64(stats.InternalStats.ValueBytes),
2832 1 : humanize.Count.Uint64(stats.InternalStats.PointsCoveredByRangeTombstones),
2833 1 : )
2834 1 : if stats.InternalStats.SeparatedPointValue.Count != 0 {
2835 1 : s.Printf(", (separated: (count %s, bytes %s, fetched %s)))",
2836 1 : humanize.Count.Uint64(stats.InternalStats.SeparatedPointValue.Count),
2837 1 : humanize.Bytes.Uint64(stats.InternalStats.SeparatedPointValue.ValueBytes),
2838 1 : humanize.Bytes.Uint64(stats.InternalStats.SeparatedPointValue.ValueBytesFetched))
2839 1 : } else {
2840 1 : s.Printf(")")
2841 1 : }
2842 : }
2843 1 : if stats.RangeKeyStats != (RangeKeyIteratorStats{}) {
2844 1 : s.SafeString(",\n(range-key-stats: ")
2845 1 : s.Printf("(count %d), (contained points: (count %d, skipped %d)))",
2846 1 : stats.RangeKeyStats.Count,
2847 1 : stats.RangeKeyStats.ContainedPoints,
2848 1 : stats.RangeKeyStats.SkippedPoints)
2849 1 : }
2850 : }
2851 :
2852 : // CanDeterministicallySingleDelete takes a valid iterator and examines internal
2853 : // state to determine if a SingleDelete deleting Iterator.Key() would
2854 : // deterministically delete the key. CanDeterministicallySingleDelete requires
2855 : // the iterator to be oriented in the forward direction (eg, the last
2856 : // positioning operation must've been a First, a Seek[Prefix]GE, or a
2857 : // Next[Prefix][WithLimit]).
2858 : //
2859 : // This function does not change the external position of the iterator, and all
2860 : // positioning methods should behave the same as if it was never called. This
2861 : // function will only return a meaningful result the first time it's invoked at
2862 : // an iterator position. This function invalidates the iterator Value's memory,
2863 : // and the caller must not rely on the memory safety of the previous Iterator
2864 : // position.
2865 : //
2866 : // If CanDeterministicallySingleDelete returns true AND the key at the iterator
2867 : // position is not modified between the creation of the Iterator and the commit
2868 : // of a batch containing a SingleDelete over the key, then the caller can be
2869 : // assured that SingleDelete is equivalent to Delete on the local engine, but it
2870 : // may not be true on another engine that received the same writes and with
2871 : // logically equivalent state since this engine may have collapsed multiple SETs
2872 : // into one.
2873 1 : func CanDeterministicallySingleDelete(it *Iterator) (bool, error) {
2874 1 : // This function may only be called once per external iterator position. We
2875 1 : // can validate this by checking the last positioning operation.
2876 1 : if it.lastPositioningOp == internalNextOp {
2877 1 : return false, errors.New("pebble: CanDeterministicallySingleDelete called twice")
2878 1 : }
2879 1 : validity, kind := it.internalNext()
2880 1 : var shadowedBySingleDelete bool
2881 1 : for validity == internalNextValid {
2882 1 : switch kind {
2883 1 : case InternalKeyKindDelete, InternalKeyKindDeleteSized:
2884 1 : // A DEL or DELSIZED tombstone is okay. An internal key
2885 1 : // sequence like SINGLEDEL; SET; DEL; SET can be handled
2886 1 : // deterministically. If there are SETs further down, we
2887 1 : // don't care about them.
2888 1 : return true, nil
2889 1 : case InternalKeyKindSingleDelete:
2890 1 : // A SingleDelete is okay as long as when that SingleDelete was
2891 1 : // written, it was written deterministically (eg, with its own
2892 1 : // CanDeterministicallySingleDelete check). Validate that it was
2893 1 : // written deterministically. We'll allow one set to appear after
2894 1 : // the SingleDelete.
2895 1 : shadowedBySingleDelete = true
2896 1 : validity, kind = it.internalNext()
2897 1 : continue
2898 1 : case InternalKeyKindSet, InternalKeyKindSetWithDelete, InternalKeyKindMerge:
2899 1 : // If we observed a single delete, it's allowed to delete 1 key.
2900 1 : // We'll keep looping to validate that the internal keys beneath the
2901 1 : // already-written single delete are copacetic.
2902 1 : if shadowedBySingleDelete {
2903 1 : shadowedBySingleDelete = false
2904 1 : validity, kind = it.internalNext()
2905 1 : continue
2906 : }
2907 : // We encountered a shadowed SET, SETWITHDEL, MERGE. A SINGLEDEL
2908 : // that deleted the KV at the original iterator position could
2909 : // result in this key becoming visible.
2910 1 : return false, nil
2911 0 : case InternalKeyKindRangeDelete:
2912 0 : // RangeDeletes are handled by the merging iterator and should never
2913 0 : // be observed by the top-level Iterator.
2914 0 : panic(errors.AssertionFailedf("pebble: unexpected range delete"))
2915 0 : case InternalKeyKindRangeKeySet, InternalKeyKindRangeKeyUnset, InternalKeyKindRangeKeyDelete:
2916 0 : // Range keys are interleaved at the maximal sequence number and
2917 0 : // should never be observed within a user key.
2918 0 : panic(errors.AssertionFailedf("pebble: unexpected range key"))
2919 0 : default:
2920 0 : panic(errors.AssertionFailedf("pebble: unexpected key kind: %s", errors.Safe(kind)))
2921 : }
2922 : }
2923 1 : if validity == internalNextError {
2924 1 : return false, it.Error()
2925 1 : }
2926 1 : return true, nil
2927 : }
2928 :
2929 : // internalNextValidity enumerates the potential outcomes of a call to
2930 : // internalNext.
2931 : type internalNextValidity int8
2932 :
2933 : const (
2934 : // internalNextError is returned by internalNext when an error occurred and
2935 : // the caller is responsible for checking iter.Error().
2936 : internalNextError internalNextValidity = iota
2937 : // internalNextExhausted is returned by internalNext when the next internal
2938 : // key is an internal key with a different user key than Iterator.Key().
2939 : internalNextExhausted
2940 : // internalNextValid is returned by internalNext when the internal next
2941 : // found a shadowed internal key with a user key equal to Iterator.Key().
2942 : internalNextValid
2943 : )
2944 :
2945 : // internalNext advances internal Iterator state forward to expose the
2946 : // InternalKeyKind of the next internal key with a user key equal to Key().
2947 : //
2948 : // internalNext is a highly specialized operation and is unlikely to be
2949 : // generally useful. See Iterator.Next for how to reposition the iterator to the
2950 : // next key. internalNext requires the Iterator to be at a valid position in the
2951 : // forward direction (the last positioning operation must've been a First, a
2952 : // Seek[Prefix]GE, or a Next[Prefix][WithLimit] and Valid() must return true).
2953 : //
2954 : // internalNext, unlike all other Iterator methods, exposes internal LSM state.
2955 : // internalNext advances the Iterator's internal iterator to the next shadowed
2956 : // key with a user key equal to Key(). When a key is overwritten or deleted, its
2957 : // removal from the LSM occurs lazily as a part of compactions. internalNext
2958 : // allows the caller to see whether an obsolete internal key exists with the
2959 : // current Key(), and what it's key kind is. Note that the existence of an
2960 : // internal key is nondeterministic and dependent on internal LSM state. These
2961 : // semantics are unlikely to be applicable to almost all use cases.
2962 : //
2963 : // If internalNext finds a key that shares the same user key as Key(), it
2964 : // returns internalNextValid and the internal key's kind. If internalNext
2965 : // encounters an error, it returns internalNextError and the caller is expected
2966 : // to call Iterator.Error() to retrieve it. In all other circumstances,
2967 : // internalNext returns internalNextExhausted, indicating that there are no more
2968 : // additional internal keys with the user key Key().
2969 : //
2970 : // internalNext does not change the external position of the iterator, and a
2971 : // Next operation should behave the same as if internalNext was never called.
2972 : // internalNext does invalidate the iterator Value's memory, and the caller must
2973 : // not rely on the memory safety of the previous Iterator position.
2974 1 : func (i *Iterator) internalNext() (internalNextValidity, base.InternalKeyKind) {
2975 1 : i.stats.ForwardStepCount[InterfaceCall]++
2976 1 : if i.err != nil {
2977 1 : return internalNextError, base.InternalKeyKindInvalid
2978 1 : } else if i.iterValidityState != IterValid {
2979 1 : return internalNextExhausted, base.InternalKeyKindInvalid
2980 1 : }
2981 1 : i.lastPositioningOp = internalNextOp
2982 1 :
2983 1 : switch i.pos {
2984 1 : case iterPosCurForward:
2985 1 : i.iterKey, i.iterValue = i.iter.Next()
2986 1 : if i.iterKey == nil {
2987 1 : // We check i.iter.Error() here and return an internalNextError enum
2988 1 : // variant so that the caller does not need to check i.iter.Error()
2989 1 : // in the common case that the next internal key has a new user key.
2990 1 : if i.err = i.iter.Error(); i.err != nil {
2991 0 : return internalNextError, base.InternalKeyKindInvalid
2992 0 : }
2993 1 : i.pos = iterPosNext
2994 1 : return internalNextExhausted, base.InternalKeyKindInvalid
2995 1 : } else if i.comparer.Equal(i.iterKey.UserKey, i.key) {
2996 1 : return internalNextValid, i.iterKey.Kind()
2997 1 : }
2998 1 : i.pos = iterPosNext
2999 1 : return internalNextExhausted, base.InternalKeyKindInvalid
3000 1 : case iterPosCurReverse, iterPosCurReversePaused, iterPosPrev:
3001 1 : i.err = errors.New("switching from reverse to forward via internalNext is prohibited")
3002 1 : i.iterValidityState = IterExhausted
3003 1 : return internalNextError, base.InternalKeyKindInvalid
3004 1 : case iterPosNext, iterPosCurForwardPaused:
3005 1 : // The previous method already moved onto the next user key. This is
3006 1 : // only possible if
3007 1 : // - the last positioning method was a call to internalNext, and we
3008 1 : // advanced to a new user key.
3009 1 : // - the previous non-internalNext iterator operation encountered a
3010 1 : // range key or merge, forcing an internal Next that found a new
3011 1 : // user key that's not equal to i.Iterator.Key().
3012 1 : return internalNextExhausted, base.InternalKeyKindInvalid
3013 0 : default:
3014 0 : panic("unreachable")
3015 : }
3016 : }
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