Line data Source code
1 : // Copyright 2021 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 keyspan
6 :
7 : import (
8 : "context"
9 : "fmt"
10 :
11 : "github.com/cockroachdb/errors"
12 : "github.com/cockroachdb/pebble/internal/base"
13 : "github.com/cockroachdb/pebble/internal/invariants"
14 : )
15 :
16 : // A SpanMask may be used to configure an interleaving iterator to skip point
17 : // keys that fall within the bounds of some spans.
18 : type SpanMask interface {
19 : // SpanChanged is invoked by an interleaving iterator whenever the current
20 : // span changes. As the iterator passes into or out of a Span, it invokes
21 : // SpanChanged, passing the new Span. When the iterator passes out of a
22 : // span's boundaries and is no longer covered by any span, SpanChanged is
23 : // invoked with a nil span.
24 : //
25 : // SpanChanged is invoked before SkipPoint, and callers may use SpanChanged
26 : // to recalculate state used by SkipPoint for masking.
27 : //
28 : // SpanChanged may be invoked consecutively with identical spans under some
29 : // circumstances, such as repeatedly absolutely positioning an iterator to
30 : // positions covered by the same span, or while changing directions.
31 : SpanChanged(*Span)
32 : // SkipPoint is invoked by the interleaving iterator whenever the iterator
33 : // encounters a point key covered by a Span. If SkipPoint returns true, the
34 : // interleaving iterator skips the point key and all larger keys with the
35 : // same prefix. This is used during range key iteration to skip over point
36 : // keys 'masked' by range keys.
37 : SkipPoint(userKey []byte) bool
38 : }
39 :
40 : // InterleavingIter combines an iterator over point keys with an iterator over
41 : // key spans.
42 : //
43 : // Throughout Pebble, some keys apply at single discrete points within the user
44 : // keyspace. Other keys apply over continuous spans of the user key space.
45 : // Internally, iterators over point keys adhere to the base.InternalIterator
46 : // interface, and iterators over spans adhere to the keyspan.FragmentIterator
47 : // interface. The InterleavingIterator wraps a point iterator and span iterator,
48 : // providing access to all the elements of both iterators.
49 : //
50 : // The InterleavingIterator implements the point base.InternalIterator
51 : // interface. After any of the iterator's methods return a key, a caller may
52 : // call Span to retrieve the span covering the returned key, if any. A span is
53 : // considered to 'cover' a returned key if the span's [start, end) bounds
54 : // include the key's user key.
55 : //
56 : // In addition to tracking the current covering span, InterleavingIter returns a
57 : // special InternalKey at span start boundaries. Start boundaries are surfaced
58 : // as a synthetic span marker: an InternalKey with the boundary as the user key,
59 : // the infinite sequence number and a key kind selected from an arbitrary key
60 : // the infinite sequence number and an arbitrary contained key's kind. Since
61 : // which of the Span's key's kind is surfaced is undefined, the caller should
62 : // not use the InternalKey's kind. The caller should only rely on the `Span`
63 : // method for retrieving information about spanning keys. The interleaved
64 : // synthetic keys have the infinite sequence number so that they're interleaved
65 : // before any point keys with the same user key when iterating forward and after
66 : // when iterating backward.
67 : //
68 : // Interleaving the synthetic start key boundaries at the maximum sequence
69 : // number provides an opportunity for the higher-level, public Iterator to
70 : // observe the Span, even if no live points keys exist within the boudns of the
71 : // Span.
72 : //
73 : // When returning a synthetic marker key for a start boundary, InterleavingIter
74 : // will truncate the span's start bound to the SeekGE or SeekPrefixGE search
75 : // key. For example, a SeekGE("d") that finds a span [a, z) may return a
76 : // synthetic span marker key `d#72057594037927935,21`.
77 : //
78 : // If bounds have been applied to the iterator through SetBounds,
79 : // InterleavingIter will truncate the bounds of spans returned through Span to
80 : // the set bounds. The bounds returned through Span are not truncated by a
81 : // SeekGE or SeekPrefixGE search key. Consider, for example SetBounds('c', 'e'),
82 : // with an iterator containing the Span [a,z):
83 : //
84 : // First() = `c#72057594037927935,21` Span() = [c,e)
85 : // SeekGE('d') = `d#72057594037927935,21` Span() = [c,e)
86 : //
87 : // InterleavedIter does not interleave synthetic markers for spans that do not
88 : // contain any keys.
89 : //
90 : // # SpanMask
91 : //
92 : // InterelavingIter takes a SpanMask parameter that may be used to configure the
93 : // behavior of the iterator. See the documentation on the SpanMask type.
94 : //
95 : // All spans containing keys are exposed during iteration.
96 : type InterleavingIter struct {
97 : cmp base.Compare
98 : comparer *base.Comparer
99 : pointIter base.InternalIterator
100 : keyspanIter FragmentIterator
101 : mask SpanMask
102 :
103 : // lower and upper hold the iteration bounds set through SetBounds.
104 : lower, upper []byte
105 : // keyBuf is used to copy SeekGE or SeekPrefixGE arguments when they're used
106 : // to truncate a span. The byte slices backing a SeekGE/SeekPrefixGE search
107 : // keys can come directly from the end user, so they're copied into keyBuf
108 : // to ensure key stability.
109 : keyBuf []byte
110 : // nextPrefixBuf is used during SeekPrefixGE calls to store the truncated
111 : // upper bound of the returned spans. SeekPrefixGE truncates the returned
112 : // spans to an upper bound of the seeked prefix's immediate successor.
113 : nextPrefixBuf []byte
114 : pointKey *base.InternalKey
115 : pointVal base.LazyValue
116 : // err holds an iterator error from either pointIter or keyspanIter. It's
117 : // reset to nil on seeks. An overview of error-handling mechanics:
118 : //
119 : // Whenever either pointIter or keyspanIter is respositioned and a nil
120 : // key/span is returned, the code performing the positioning is responsible
121 : // for checking the iterator's Error() value. This happens in savePoint and
122 : // saveSpan[Forward,Backward].
123 : //
124 : // Once i.err is non-nil, the computation of i.pos must set i.pos =
125 : // posExhausted. This happens in compute[Smallest|Largest]Pos and
126 : // [next|prev]Pos. Setting i.pos to posExhausted ensures we'll yield nil to
127 : // the caller, which they'll interpret as a signal they must check Error().
128 : //
129 : // INVARIANTS:
130 : // i.err != nil => i.pos = posExhausted
131 : err error
132 : // prefix records the iterator's current prefix if the iterator is in prefix
133 : // mode. During prefix mode, Pebble will truncate spans to the next prefix.
134 : // If the iterator subsequently leaves prefix mode, the existing span cached
135 : // in i.span must be invalidated because its bounds do not reflect the
136 : // original span's true bounds.
137 : prefix []byte
138 : // span holds the span at the keyspanIter's current position. If the span is
139 : // wholly contained within the iterator bounds, this span is directly
140 : // returned to the iterator consumer through Span(). If either bound needed
141 : // to be truncated to the iterator bounds, then truncated is set to true and
142 : // Span() must return a pointer to truncatedSpan.
143 : span *Span
144 : // spanMarker holds the synthetic key that is returned when the iterator
145 : // passes over a key span's start bound.
146 : spanMarker base.InternalKey
147 : // truncated indicates whether or not the span at the current position
148 : // needed to be truncated. If it did, truncatedSpan holds the truncated
149 : // span that should be returned.
150 : truncatedSpan Span
151 : truncated bool
152 :
153 : // Keeping all of the bools/uint8s together reduces the sizeof the struct.
154 :
155 : // pos encodes the current position of the iterator: exhausted, on the point
156 : // key, on a keyspan start, or on a keyspan end.
157 : pos interleavePos
158 : // withinSpan indicates whether the iterator is currently positioned within
159 : // the bounds of the current span (i.span). withinSpan must be updated
160 : // whenever the interleaving iterator's position enters or exits the bounds
161 : // of a span.
162 : withinSpan bool
163 : // spanMarkerTruncated is set by SeekGE/SeekPrefixGE calls that truncate a
164 : // span's start bound marker to the search key. It's returned to false on
165 : // the next repositioning of the keyspan iterator.
166 : spanMarkerTruncated bool
167 : // maskSpanChangedCalled records whether or not the last call to
168 : // SpanMask.SpanChanged provided the current span (i.span) or not.
169 : maskSpanChangedCalled bool
170 : // dir indicates the direction of iteration: forward (+1) or backward (-1)
171 : dir int8
172 : }
173 :
174 : // interleavePos indicates the iterator's current position. Note that both
175 : // keyspanStart and keyspanEnd positions correspond to their user key boundaries
176 : // with maximal sequence numbers. This means in the forward direction
177 : // posKeyspanStart and posKeyspanEnd are always interleaved before a posPointKey
178 : // with the same user key.
179 : type interleavePos int8
180 :
181 : const (
182 : posUninitialized interleavePos = iota
183 : posExhausted
184 : posPointKey
185 : posKeyspanStart
186 : posKeyspanEnd
187 : )
188 :
189 : // Assert that *InterleavingIter implements the InternalIterator interface.
190 : var _ base.InternalIterator = &InterleavingIter{}
191 :
192 : // InterleavingIterOpts holds options configuring the behavior of a
193 : // InterleavingIter.
194 : type InterleavingIterOpts struct {
195 : Mask SpanMask
196 : LowerBound, UpperBound []byte
197 : }
198 :
199 : // Init initializes the InterleavingIter to interleave point keys from pointIter
200 : // with key spans from keyspanIter.
201 : //
202 : // The point iterator must already have the bounds provided on opts. Init does
203 : // not propagate the bounds down the iterator stack.
204 : func (i *InterleavingIter) Init(
205 : comparer *base.Comparer,
206 : pointIter base.InternalIterator,
207 : keyspanIter FragmentIterator,
208 : opts InterleavingIterOpts,
209 1 : ) {
210 1 : keyspanIter = MaybeAssert(keyspanIter, comparer.Compare)
211 1 : // To debug:
212 1 : // keyspanIter = InjectLogging(keyspanIter, base.DefaultLogger)
213 1 : *i = InterleavingIter{
214 1 : cmp: comparer.Compare,
215 1 : comparer: comparer,
216 1 : pointIter: pointIter,
217 1 : keyspanIter: keyspanIter,
218 1 : mask: opts.Mask,
219 1 : lower: opts.LowerBound,
220 1 : upper: opts.UpperBound,
221 1 : }
222 1 : }
223 :
224 : // InitSeekGE may be called after Init but before any positioning method.
225 : // InitSeekGE initializes the current position of the point iterator and then
226 : // performs a SeekGE on the keyspan iterator using the provided key. InitSeekGE
227 : // returns whichever point or keyspan key is smaller. After InitSeekGE, the
228 : // iterator is positioned and may be repositioned using relative positioning
229 : // methods.
230 : //
231 : // This method is used specifically for lazily constructing combined iterators.
232 : // It allows for seeding the iterator with the current position of the point
233 : // iterator.
234 : func (i *InterleavingIter) InitSeekGE(
235 : prefix, key []byte, pointKey *base.InternalKey, pointValue base.LazyValue,
236 1 : ) (*base.InternalKey, base.LazyValue) {
237 1 : i.dir = +1
238 1 : i.clearMask()
239 1 : i.prefix = prefix
240 1 : i.savePoint(pointKey, pointValue)
241 1 : // NB: This keyspanSeekGE call will truncate the span to the seek key if
242 1 : // necessary. This truncation is important for cases where a switch to
243 1 : // combined iteration is made during a user-initiated SeekGE.
244 1 : i.keyspanSeekGE(key, prefix)
245 1 : i.computeSmallestPos()
246 1 : return i.yieldPosition(key, i.nextPos)
247 1 : }
248 :
249 : // InitSeekLT may be called after Init but before any positioning method.
250 : // InitSeekLT initializes the current position of the point iterator and then
251 : // performs a SeekLT on the keyspan iterator using the provided key. InitSeekLT
252 : // returns whichever point or keyspan key is larger. After InitSeekLT, the
253 : // iterator is positioned and may be repositioned using relative positioning
254 : // methods.
255 : //
256 : // This method is used specifically for lazily constructing combined iterators.
257 : // It allows for seeding the iterator with the current position of the point
258 : // iterator.
259 : func (i *InterleavingIter) InitSeekLT(
260 : key []byte, pointKey *base.InternalKey, pointValue base.LazyValue,
261 1 : ) (*base.InternalKey, base.LazyValue) {
262 1 : i.dir = -1
263 1 : i.clearMask()
264 1 : i.savePoint(pointKey, pointValue)
265 1 : i.keyspanSeekLT(key)
266 1 : i.computeLargestPos()
267 1 : return i.yieldPosition(i.lower, i.prevPos)
268 1 : }
269 :
270 : // SeekGE implements (base.InternalIterator).SeekGE.
271 : //
272 : // If there exists a span with a start key ≤ the first matching point key,
273 : // SeekGE will return a synthetic span marker key for the span. If this span's
274 : // start key is less than key, the returned marker will be truncated to key.
275 : // Note that this search-key truncation of the marker's key is not applied to
276 : // the span returned by Span.
277 : //
278 : // NB: In accordance with the base.InternalIterator contract:
279 : //
280 : // i.lower ≤ key
281 : func (i *InterleavingIter) SeekGE(
282 : key []byte, flags base.SeekGEFlags,
283 1 : ) (*base.InternalKey, base.LazyValue) {
284 1 : i.err = nil
285 1 : i.clearMask()
286 1 : i.disablePrefixMode()
287 1 : i.savePoint(i.pointIter.SeekGE(key, flags))
288 1 :
289 1 : // We need to seek the keyspan iterator too. If the keyspan iterator was
290 1 : // already positioned at a span, we might be able to avoid the seek if the
291 1 : // seek key falls within the existing span's bounds.
292 1 : if i.span != nil && i.cmp(key, i.span.End) < 0 && i.cmp(key, i.span.Start) >= 0 {
293 1 : // We're seeking within the existing span's bounds. We still might need
294 1 : // truncate the span to the iterator's bounds.
295 1 : i.saveSpanForward(i.span, nil)
296 1 : i.savedKeyspan()
297 1 : } else {
298 1 : i.keyspanSeekGE(key, nil /* prefix */)
299 1 : }
300 :
301 1 : i.dir = +1
302 1 : i.computeSmallestPos()
303 1 : return i.yieldPosition(key, i.nextPos)
304 : }
305 :
306 : // SeekPrefixGE implements (base.InternalIterator).SeekPrefixGE.
307 : //
308 : // If there exists a span with a start key ≤ the first matching point key,
309 : // SeekPrefixGE will return a synthetic span marker key for the span. If this
310 : // span's start key is less than key, the returned marker will be truncated to
311 : // key. Note that this search-key truncation of the marker's key is not applied
312 : // to the span returned by Span.
313 : //
314 : // NB: In accordance with the base.InternalIterator contract:
315 : //
316 : // i.lower ≤ key
317 : func (i *InterleavingIter) SeekPrefixGE(
318 : prefix, key []byte, flags base.SeekGEFlags,
319 1 : ) (*base.InternalKey, base.LazyValue) {
320 1 : i.err = nil
321 1 : i.clearMask()
322 1 : i.prefix = prefix
323 1 : i.savePoint(i.pointIter.SeekPrefixGE(prefix, key, flags))
324 1 :
325 1 : // We need to seek the keyspan iterator too. If the keyspan iterator was
326 1 : // already positioned at a span, we might be able to avoid the seek if the
327 1 : // entire seek prefix key falls within the existing span's bounds.
328 1 : //
329 1 : // During a SeekPrefixGE, Pebble defragments range keys within the bounds of
330 1 : // the prefix. For example, a SeekPrefixGE('c', 'c@8') must defragment the
331 1 : // any overlapping range keys within the bounds of [c,c\00).
332 1 : //
333 1 : // If range keys are fragmented within a prefix (eg, because a version
334 1 : // within a prefix was chosen as an sstable boundary), then it's possible
335 1 : // the seek key falls into the current i.span, but the current i.span does
336 1 : // not wholly cover the seek prefix.
337 1 : //
338 1 : // For example, a SeekPrefixGE('d@5') may only defragment a range key to
339 1 : // the bounds of [c@2,e). A subsequent SeekPrefixGE('c@0') must re-seek the
340 1 : // keyspan iterator, because although 'c@0' is contained within [c@2,e), the
341 1 : // full span of the prefix is not.
342 1 : //
343 1 : // Similarly, a SeekPrefixGE('a@3') may only defragment a range key to the
344 1 : // bounds [a,c@8). A subsequent SeekPrefixGE('c@10') must re-seek the
345 1 : // keyspan iterator, because although 'c@10' is contained within [a,c@8),
346 1 : // the full span of the prefix is not.
347 1 : seekKeyspanIter := true
348 1 : if i.span != nil && i.cmp(prefix, i.span.Start) >= 0 {
349 1 : if ei := i.comparer.Split(i.span.End); i.cmp(prefix, i.span.End[:ei]) < 0 {
350 1 : // We're seeking within the existing span's bounds. We still might need
351 1 : // truncate the span to the iterator's bounds.
352 1 : i.saveSpanForward(i.span, nil)
353 1 : i.savedKeyspan()
354 1 : seekKeyspanIter = false
355 1 : }
356 : }
357 1 : if seekKeyspanIter {
358 1 : i.keyspanSeekGE(key, prefix)
359 1 : }
360 :
361 1 : i.dir = +1
362 1 : i.computeSmallestPos()
363 1 : return i.yieldPosition(key, i.nextPos)
364 : }
365 :
366 : // SeekLT implements (base.InternalIterator).SeekLT.
367 : func (i *InterleavingIter) SeekLT(
368 : key []byte, flags base.SeekLTFlags,
369 1 : ) (*base.InternalKey, base.LazyValue) {
370 1 : i.err = nil
371 1 : i.clearMask()
372 1 : i.disablePrefixMode()
373 1 : i.savePoint(i.pointIter.SeekLT(key, flags))
374 1 :
375 1 : // We need to seek the keyspan iterator too. If the keyspan iterator was
376 1 : // already positioned at a span, we might be able to avoid the seek if the
377 1 : // seek key falls within the existing span's bounds.
378 1 : if i.span != nil && i.cmp(key, i.span.Start) > 0 && i.cmp(key, i.span.End) < 0 {
379 1 : // We're seeking within the existing span's bounds. We still might need
380 1 : // truncate the span to the iterator's bounds.
381 1 : i.saveSpanBackward(i.span, nil)
382 1 : // The span's start key is still not guaranteed to be less than key,
383 1 : // because of the bounds enforcement. Consider the following example:
384 1 : //
385 1 : // Bounds are set to [d,e). The user performs a SeekLT(d). The
386 1 : // FragmentIterator.SeekLT lands on a span [b,f). This span has a start
387 1 : // key less than d, as expected. Above, saveSpanBackward truncates the
388 1 : // span to match the iterator's current bounds, modifying the span to
389 1 : // [d,e), which does not overlap the search space of [-∞, d).
390 1 : //
391 1 : // This problem is a consequence of the SeekLT's exclusive search key
392 1 : // and the fact that we don't perform bounds truncation at every leaf
393 1 : // iterator.
394 1 : if i.span != nil && i.truncated && i.cmp(i.truncatedSpan.Start, key) >= 0 {
395 1 : i.span = nil
396 1 : }
397 1 : i.savedKeyspan()
398 1 : } else {
399 1 : i.keyspanSeekLT(key)
400 1 : }
401 :
402 1 : i.dir = -1
403 1 : i.computeLargestPos()
404 1 : return i.yieldPosition(i.lower, i.prevPos)
405 : }
406 :
407 : // First implements (base.InternalIterator).First.
408 1 : func (i *InterleavingIter) First() (*base.InternalKey, base.LazyValue) {
409 1 : i.err = nil
410 1 : i.clearMask()
411 1 : i.disablePrefixMode()
412 1 : i.savePoint(i.pointIter.First())
413 1 : i.saveSpanForward(i.keyspanIter.First())
414 1 : i.savedKeyspan()
415 1 : i.dir = +1
416 1 : i.computeSmallestPos()
417 1 : return i.yieldPosition(i.lower, i.nextPos)
418 1 : }
419 :
420 : // Last implements (base.InternalIterator).Last.
421 1 : func (i *InterleavingIter) Last() (*base.InternalKey, base.LazyValue) {
422 1 : i.err = nil
423 1 : i.clearMask()
424 1 : i.disablePrefixMode()
425 1 : i.savePoint(i.pointIter.Last())
426 1 : i.saveSpanBackward(i.keyspanIter.Last())
427 1 : i.savedKeyspan()
428 1 : i.dir = -1
429 1 : i.computeLargestPos()
430 1 : return i.yieldPosition(i.lower, i.prevPos)
431 1 : }
432 :
433 : // Next implements (base.InternalIterator).Next.
434 1 : func (i *InterleavingIter) Next() (*base.InternalKey, base.LazyValue) {
435 1 : if i.dir == -1 {
436 1 : // Switching directions.
437 1 : i.dir = +1
438 1 :
439 1 : if i.mask != nil {
440 1 : // Clear the mask while we reposition the point iterator. While
441 1 : // switching directions, we may move the point iterator outside of
442 1 : // i.span's bounds.
443 1 : i.clearMask()
444 1 : }
445 :
446 : // When switching directions, iterator state corresponding to the
447 : // current iterator position (as indicated by i.pos) is already correct.
448 : // However any state that has yet to be interleaved describes a position
449 : // behind the current iterator position and needs to be updated to
450 : // describe the position ahead of the current iterator position.
451 1 : switch i.pos {
452 0 : case posExhausted:
453 : // Nothing to do. The below nextPos call will move both the point
454 : // key and span to their next positions and return
455 : // MIN(point,s.Start).
456 1 : case posPointKey:
457 1 : // If we're currently on a point key, the below nextPos will
458 1 : // correctly Next the point key iterator to the next point key.
459 1 : // Do we need to move the span forwards? If the current span lies
460 1 : // entirely behind the current key (!i.withinSpan), then we
461 1 : // need to move it to the first span in the forward direction.
462 1 : if !i.withinSpan {
463 1 : i.saveSpanForward(i.keyspanIter.Next())
464 1 : i.savedKeyspan()
465 1 : }
466 1 : case posKeyspanStart:
467 1 : i.withinSpan = true
468 1 : // Since we're positioned on a Span, the pointIter is positioned
469 1 : // entirely behind the current iterator position. Reposition it
470 1 : // ahead of the current iterator position.
471 1 : i.savePoint(i.pointIter.Next())
472 0 : case posKeyspanEnd:
473 0 : // Since we're positioned on a Span, the pointIter is positioned
474 0 : // entirely behind of the current iterator position. Reposition it
475 0 : // ahead the current iterator position.
476 0 : i.savePoint(i.pointIter.Next())
477 : }
478 : // Fallthrough to calling i.nextPos.
479 : }
480 1 : i.nextPos()
481 1 : return i.yieldPosition(i.lower, i.nextPos)
482 : }
483 :
484 : // NextPrefix implements (base.InternalIterator).NextPrefix.
485 1 : func (i *InterleavingIter) NextPrefix(succKey []byte) (*base.InternalKey, base.LazyValue) {
486 1 : if i.dir == -1 {
487 0 : panic("pebble: cannot switch directions with NextPrefix")
488 : }
489 :
490 1 : switch i.pos {
491 1 : case posExhausted:
492 1 : return nil, base.LazyValue{}
493 1 : case posPointKey:
494 1 : i.savePoint(i.pointIter.NextPrefix(succKey))
495 1 : if i.withinSpan {
496 1 : if i.pointKey == nil || i.cmp(i.span.End, i.pointKey.UserKey) <= 0 {
497 1 : i.pos = posKeyspanEnd
498 1 : } else {
499 1 : i.pos = posPointKey
500 1 : }
501 1 : } else {
502 1 : i.computeSmallestPos()
503 1 : }
504 1 : case posKeyspanStart, posKeyspanEnd:
505 1 : i.nextPos()
506 : }
507 1 : return i.yieldPosition(i.lower, i.nextPos)
508 : }
509 :
510 : // Prev implements (base.InternalIterator).Prev.
511 1 : func (i *InterleavingIter) Prev() (*base.InternalKey, base.LazyValue) {
512 1 : if i.dir == +1 {
513 1 : // Switching directions.
514 1 : i.dir = -1
515 1 :
516 1 : if i.mask != nil {
517 1 : // Clear the mask while we reposition the point iterator. While
518 1 : // switching directions, we may move the point iterator outside of
519 1 : // i.span's bounds.
520 1 : i.clearMask()
521 1 : }
522 :
523 : // When switching directions, iterator state corresponding to the
524 : // current iterator position (as indicated by i.pos) is already correct.
525 : // However any state that has yet to be interleaved describes a position
526 : // ahead of the current iterator position and needs to be updated to
527 : // describe the position behind the current iterator position.
528 1 : switch i.pos {
529 0 : case posExhausted:
530 : // Nothing to do. The below prevPos call will move both the point
531 : // key and span to previous positions and return MAX(point, s.End).
532 1 : case posPointKey:
533 1 : // If we're currently on a point key, the point iterator is in the
534 1 : // right place and the call to prevPos will correctly Prev the point
535 1 : // key iterator to the previous point key. Do we need to move the
536 1 : // span backwards? If the current span lies entirely ahead of the
537 1 : // current key (!i.withinSpan), then we need to move it to the first
538 1 : // span in the reverse direction.
539 1 : if !i.withinSpan {
540 1 : i.saveSpanBackward(i.keyspanIter.Prev())
541 1 : i.savedKeyspan()
542 1 : }
543 1 : case posKeyspanStart:
544 1 : // Since we're positioned on a Span, the pointIter is positioned
545 1 : // entirely ahead of the current iterator position. Reposition it
546 1 : // behind the current iterator position.
547 1 : i.savePoint(i.pointIter.Prev())
548 1 : // Without considering truncation of spans to seek keys, the keyspan
549 1 : // iterator is already in the right place. But consider span [a, z)
550 1 : // and this sequence of iterator calls:
551 1 : //
552 1 : // SeekGE('c') = c.RANGEKEYSET#72057594037927935
553 1 : // Prev() = a.RANGEKEYSET#72057594037927935
554 1 : //
555 1 : // If the current span's start key was last surfaced truncated due
556 1 : // to a SeekGE or SeekPrefixGE call, then it's still relevant in the
557 1 : // reverse direction with an untruncated start key.
558 1 : if i.spanMarkerTruncated {
559 1 : // When we fallthrough to calling prevPos, we want to move to
560 1 : // MAX(point, span.Start). We cheat here by claiming we're
561 1 : // currently on the end boundary, so that we'll move on to the
562 1 : // untruncated start key if necessary.
563 1 : i.pos = posKeyspanEnd
564 1 : }
565 0 : case posKeyspanEnd:
566 0 : // Since we're positioned on a Span, the pointIter is positioned
567 0 : // entirely ahead of the current iterator position. Reposition it
568 0 : // behind the current iterator position.
569 0 : i.savePoint(i.pointIter.Prev())
570 : }
571 :
572 1 : if i.spanMarkerTruncated {
573 1 : // Save the keyspan again to clear truncation.
574 1 : i.savedKeyspan()
575 1 : }
576 : // Fallthrough to calling i.prevPos.
577 : }
578 1 : i.prevPos()
579 1 : return i.yieldPosition(i.lower, i.prevPos)
580 : }
581 :
582 : // computeSmallestPos sets i.{pos,withinSpan} to:
583 : //
584 : // MIN(i.pointKey, i.span.Start)
585 1 : func (i *InterleavingIter) computeSmallestPos() {
586 1 : if i.err == nil {
587 1 : if i.span != nil && (i.pointKey == nil || i.cmp(i.startKey(), i.pointKey.UserKey) <= 0) {
588 1 : i.withinSpan = true
589 1 : i.pos = posKeyspanStart
590 1 : return
591 1 : }
592 1 : i.withinSpan = false
593 1 : if i.pointKey != nil {
594 1 : i.pos = posPointKey
595 1 : return
596 1 : }
597 : }
598 1 : i.pos = posExhausted
599 : }
600 :
601 : // computeLargestPos sets i.{pos,withinSpan} to:
602 : //
603 : // MAX(i.pointKey, i.span.End)
604 1 : func (i *InterleavingIter) computeLargestPos() {
605 1 : if i.err == nil {
606 1 : if i.span != nil && (i.pointKey == nil || i.cmp(i.span.End, i.pointKey.UserKey) > 0) {
607 1 : i.withinSpan = true
608 1 : i.pos = posKeyspanEnd
609 1 : return
610 1 : }
611 1 : i.withinSpan = false
612 1 : if i.pointKey != nil {
613 1 : i.pos = posPointKey
614 1 : return
615 1 : }
616 : }
617 1 : i.pos = posExhausted
618 : }
619 :
620 : // nextPos advances the iterator one position in the forward direction.
621 1 : func (i *InterleavingIter) nextPos() {
622 1 : if invariants.Enabled {
623 1 : defer func() {
624 1 : if i.err != nil && i.pos != posExhausted {
625 0 : panic(errors.AssertionFailedf("iterator has accumulated error but i.pos = %d", i.pos))
626 : }
627 : }()
628 : }
629 : // NB: If i.err != nil or any of the positioning methods performed in this
630 : // function result in i.err != nil, we must set i.pos = posExhausted. We
631 : // perform this check explicitly here, but if any of the branches below
632 : // advance either iterator, they must also check i.err and set posExhausted
633 : // if necessary.
634 1 : if i.err != nil {
635 1 : i.pos = posExhausted
636 1 : return
637 1 : }
638 :
639 1 : switch i.pos {
640 1 : case posExhausted:
641 1 : i.savePoint(i.pointIter.Next())
642 1 : i.saveSpanForward(i.keyspanIter.Next())
643 1 : i.savedKeyspan()
644 1 : i.computeSmallestPos()
645 1 : case posPointKey:
646 1 : i.savePoint(i.pointIter.Next())
647 1 : if i.err != nil {
648 1 : i.pos = posExhausted
649 1 : return
650 1 : }
651 : // If we're not currently within the span, we want to chose the
652 : // MIN(pointKey,span.Start), which is exactly the calculation performed
653 : // by computeSmallestPos.
654 1 : if !i.withinSpan {
655 1 : i.computeSmallestPos()
656 1 : return
657 1 : }
658 : // i.withinSpan=true
659 : // Since we previously were within the span, we want to choose the
660 : // MIN(pointKey,span.End).
661 1 : switch {
662 0 : case i.span == nil:
663 0 : panic("i.withinSpan=true and i.span=nil")
664 1 : case i.pointKey == nil:
665 1 : // Since i.withinSpan=true, we step onto the end boundary of the
666 1 : // keyspan.
667 1 : i.pos = posKeyspanEnd
668 1 : default:
669 1 : // i.withinSpan && i.pointKey != nil && i.span != nil
670 1 : if i.cmp(i.span.End, i.pointKey.UserKey) <= 0 {
671 1 : i.pos = posKeyspanEnd
672 1 : } else {
673 1 : i.pos = posPointKey
674 1 : }
675 : }
676 1 : case posKeyspanStart:
677 1 : // Either a point key or the span's end key comes next.
678 1 : if i.pointKey != nil && i.cmp(i.pointKey.UserKey, i.span.End) < 0 {
679 1 : i.pos = posPointKey
680 1 : } else {
681 1 : i.pos = posKeyspanEnd
682 1 : }
683 1 : case posKeyspanEnd:
684 1 : i.saveSpanForward(i.keyspanIter.Next())
685 1 : i.savedKeyspan()
686 1 : i.computeSmallestPos()
687 0 : default:
688 0 : panic(fmt.Sprintf("unexpected pos=%d", i.pos))
689 : }
690 : }
691 :
692 : // prevPos advances the iterator one position in the reverse direction.
693 1 : func (i *InterleavingIter) prevPos() {
694 1 : if invariants.Enabled {
695 1 : defer func() {
696 1 : if i.err != nil && i.pos != posExhausted {
697 0 : panic(errors.AssertionFailedf("iterator has accumulated error but i.pos = %d", i.pos))
698 : }
699 : }()
700 : }
701 : // NB: If i.err != nil or any of the positioning methods performed in this
702 : // function result in i.err != nil, we must set i.pos = posExhausted. We
703 : // perform this check explicitly here, but if any of the branches below
704 : // advance either iterator, they must also check i.err and set posExhausted
705 : // if necessary.
706 1 : if i.err != nil {
707 1 : i.pos = posExhausted
708 1 : return
709 1 : }
710 :
711 1 : switch i.pos {
712 1 : case posExhausted:
713 1 : i.savePoint(i.pointIter.Prev())
714 1 : i.saveSpanBackward(i.keyspanIter.Prev())
715 1 : i.savedKeyspan()
716 1 : i.computeLargestPos()
717 1 : case posPointKey:
718 1 : i.savePoint(i.pointIter.Prev())
719 1 : if i.err != nil {
720 1 : i.pos = posExhausted
721 1 : return
722 1 : }
723 : // If we're not currently covered by the span, we want to chose the
724 : // MAX(pointKey,span.End), which is exactly the calculation performed
725 : // by computeLargestPos.
726 1 : if !i.withinSpan {
727 1 : i.computeLargestPos()
728 1 : return
729 1 : }
730 1 : switch {
731 0 : case i.span == nil:
732 0 : panic("withinSpan=true, but i.span == nil")
733 1 : case i.pointKey == nil:
734 1 : i.pos = posKeyspanEnd
735 1 : default:
736 1 : // i.withinSpan && i.pointKey != nil && i.span != nil
737 1 : if i.cmp(i.span.Start, i.pointKey.UserKey) > 0 {
738 1 : i.pos = posKeyspanStart
739 1 : } else {
740 1 : i.pos = posPointKey
741 1 : }
742 : }
743 1 : case posKeyspanStart:
744 1 : i.saveSpanBackward(i.keyspanIter.Prev())
745 1 : i.savedKeyspan()
746 1 : i.computeLargestPos()
747 1 : case posKeyspanEnd:
748 1 : // Either a point key or the span's start key is previous.
749 1 : if i.pointKey != nil && i.cmp(i.pointKey.UserKey, i.span.Start) >= 0 {
750 1 : i.pos = posPointKey
751 1 : } else {
752 1 : i.pos = posKeyspanStart
753 1 : }
754 0 : default:
755 0 : panic(fmt.Sprintf("unexpected pos=%d", i.pos))
756 : }
757 : }
758 :
759 : func (i *InterleavingIter) yieldPosition(
760 : lowerBound []byte, advance func(),
761 1 : ) (*base.InternalKey, base.LazyValue) {
762 1 : // This loop returns the first visible position in the current iteration
763 1 : // direction. Some positions are not visible and skipped. For example, if
764 1 : // masking is enabled and the iterator is positioned over a masked point
765 1 : // key, this loop skips the position. If a span's start key should be
766 1 : // interleaved next, but the span is empty, the loop continues to the next
767 1 : // key. Currently, span end keys are also always skipped, and are used only
768 1 : // for maintaining internal state.
769 1 : for {
770 1 : switch i.pos {
771 1 : case posExhausted:
772 1 : return i.yieldNil()
773 1 : case posPointKey:
774 1 : if i.pointKey == nil {
775 0 : panic("i.pointKey is nil")
776 : }
777 :
778 1 : if i.mask != nil {
779 1 : i.maybeUpdateMask()
780 1 : if i.withinSpan && i.mask.SkipPoint(i.pointKey.UserKey) {
781 1 : // The span covers the point key. If a SkipPoint hook is
782 1 : // configured, ask it if we should skip this point key.
783 1 : if i.prefix != nil {
784 1 : // During prefix-iteration node, once a point is masked,
785 1 : // all subsequent keys with the same prefix must also be
786 1 : // masked according to the key ordering. We can stop and
787 1 : // return nil.
788 1 : //
789 1 : // NB: The above is not just an optimization. During
790 1 : // prefix-iteration mode, the internal iterator contract
791 1 : // prohibits us from Next-ing beyond the first key
792 1 : // beyond the iteration prefix. If we didn't already
793 1 : // stop early, we would need to check if this masked
794 1 : // point is already beyond the prefix.
795 1 : return i.yieldNil()
796 1 : }
797 : // TODO(jackson): If we thread a base.Comparer through to
798 : // InterleavingIter so that we have access to
799 : // ImmediateSuccessor, we could use NextPrefix. We'd need to
800 : // tweak the SpanMask interface slightly.
801 :
802 : // Advance beyond the masked point key.
803 1 : advance()
804 1 : continue
805 : }
806 : }
807 1 : return i.yieldPointKey()
808 1 : case posKeyspanEnd:
809 1 : // Don't interleave end keys; just advance.
810 1 : advance()
811 1 : continue
812 1 : case posKeyspanStart:
813 1 : // Don't interleave an empty span.
814 1 : if i.span.Empty() {
815 1 : advance()
816 1 : continue
817 : }
818 1 : return i.yieldSyntheticSpanMarker(lowerBound)
819 0 : default:
820 0 : panic(fmt.Sprintf("unexpected interleavePos=%d", i.pos))
821 : }
822 : }
823 : }
824 :
825 : // keyspanSeekGE seeks the keyspan iterator to the first span covering a key ≥ k.
826 1 : func (i *InterleavingIter) keyspanSeekGE(k []byte, prefix []byte) {
827 1 : i.saveSpanForward(i.keyspanIter.SeekGE(k))
828 1 : i.savedKeyspan()
829 1 : }
830 :
831 : // keyspanSeekLT seeks the keyspan iterator to the last span covering a key < k.
832 1 : func (i *InterleavingIter) keyspanSeekLT(k []byte) {
833 1 : i.saveSpanBackward(i.keyspanIter.SeekLT(k))
834 1 : // The current span's start key is not guaranteed to be less than key,
835 1 : // because of the bounds enforcement. Consider the following example:
836 1 : //
837 1 : // Bounds are set to [d,e). The user performs a SeekLT(d). The
838 1 : // FragmentIterator.SeekLT lands on a span [b,f). This span has a start key
839 1 : // less than d, as expected. Above, saveSpanBackward truncates the span to
840 1 : // match the iterator's current bounds, modifying the span to [d,e), which
841 1 : // does not overlap the search space of [-∞, d).
842 1 : //
843 1 : // This problem is a consequence of the SeekLT's exclusive search key and
844 1 : // the fact that we don't perform bounds truncation at every leaf iterator.
845 1 : if i.span != nil && i.truncated && i.cmp(i.truncatedSpan.Start, k) >= 0 {
846 1 : i.span = nil
847 1 : }
848 1 : i.savedKeyspan()
849 : }
850 :
851 1 : func (i *InterleavingIter) saveSpanForward(span *Span, err error) {
852 1 : i.span = span
853 1 : i.err = firstError(i.err, err)
854 1 : i.truncated = false
855 1 : i.truncatedSpan = Span{}
856 1 : if i.span == nil {
857 1 : return
858 1 : }
859 : // Check the upper bound if we have one.
860 1 : if i.upper != nil && i.cmp(i.span.Start, i.upper) >= 0 {
861 1 : i.span = nil
862 1 : return
863 1 : }
864 :
865 : // TODO(jackson): The key comparisons below truncate bounds whenever the
866 : // keyspan iterator is repositioned. We could perform this lazily, and do it
867 : // the first time the user actually asks for this span's bounds in
868 : // SpanBounds. This would reduce work in the case where there's no span
869 : // covering the point and the keyspan iterator is non-empty.
870 :
871 : // NB: These truncations don't require setting `keyspanMarkerTruncated`:
872 : // That flag only applies to truncated span marker keys.
873 1 : if i.lower != nil && i.cmp(i.span.Start, i.lower) < 0 {
874 1 : i.truncated = true
875 1 : i.truncatedSpan = *i.span
876 1 : i.truncatedSpan.Start = i.lower
877 1 : }
878 1 : if i.upper != nil && i.cmp(i.upper, i.span.End) < 0 {
879 1 : if !i.truncated {
880 1 : i.truncated = true
881 1 : i.truncatedSpan = *i.span
882 1 : }
883 1 : i.truncatedSpan.End = i.upper
884 : }
885 : // If this is a part of a SeekPrefixGE call, we may also need to truncate to
886 : // the prefix's bounds.
887 1 : if i.prefix != nil {
888 1 : if !i.truncated {
889 1 : i.truncated = true
890 1 : i.truncatedSpan = *i.span
891 1 : }
892 1 : if i.cmp(i.prefix, i.truncatedSpan.Start) > 0 {
893 1 : i.truncatedSpan.Start = i.prefix
894 1 : }
895 1 : i.nextPrefixBuf = i.comparer.ImmediateSuccessor(i.nextPrefixBuf[:0], i.prefix)
896 1 : if i.truncated && i.cmp(i.nextPrefixBuf, i.truncatedSpan.End) < 0 {
897 1 : i.truncatedSpan.End = i.nextPrefixBuf
898 1 : }
899 : }
900 :
901 1 : if i.truncated && i.comparer.Equal(i.truncatedSpan.Start, i.truncatedSpan.End) {
902 1 : i.span = nil
903 1 : }
904 : }
905 :
906 1 : func (i *InterleavingIter) saveSpanBackward(span *Span, err error) {
907 1 : i.span = span
908 1 : i.err = firstError(i.err, err)
909 1 : i.truncated = false
910 1 : i.truncatedSpan = Span{}
911 1 : if i.span == nil {
912 1 : return
913 1 : }
914 :
915 : // Check the lower bound if we have one.
916 1 : if i.lower != nil && i.cmp(i.span.End, i.lower) <= 0 {
917 0 : i.span = nil
918 0 : return
919 0 : }
920 :
921 : // TODO(jackson): The key comparisons below truncate bounds whenever the
922 : // keyspan iterator is repositioned. We could perform this lazily, and do it
923 : // the first time the user actually asks for this span's bounds in
924 : // SpanBounds. This would reduce work in the case where there's no span
925 : // covering the point and the keyspan iterator is non-empty.
926 :
927 : // NB: These truncations don't require setting `keyspanMarkerTruncated`:
928 : // That flag only applies to truncated span marker keys.
929 1 : if i.lower != nil && i.cmp(i.span.Start, i.lower) < 0 {
930 1 : i.truncated = true
931 1 : i.truncatedSpan = *i.span
932 1 : i.truncatedSpan.Start = i.lower
933 1 : }
934 1 : if i.upper != nil && i.cmp(i.upper, i.span.End) < 0 {
935 1 : if !i.truncated {
936 1 : i.truncated = true
937 1 : i.truncatedSpan = *i.span
938 1 : }
939 1 : i.truncatedSpan.End = i.upper
940 : }
941 1 : if i.truncated && i.comparer.Equal(i.truncatedSpan.Start, i.truncatedSpan.End) {
942 1 : i.span = nil
943 1 : }
944 : }
945 :
946 1 : func (i *InterleavingIter) yieldNil() (*base.InternalKey, base.LazyValue) {
947 1 : i.withinSpan = false
948 1 : i.clearMask()
949 1 : return i.verify(nil, base.LazyValue{})
950 1 : }
951 :
952 1 : func (i *InterleavingIter) yieldPointKey() (*base.InternalKey, base.LazyValue) {
953 1 : return i.verify(i.pointKey, i.pointVal)
954 1 : }
955 :
956 : func (i *InterleavingIter) yieldSyntheticSpanMarker(
957 : lowerBound []byte,
958 1 : ) (*base.InternalKey, base.LazyValue) {
959 1 : i.spanMarker.UserKey = i.startKey()
960 1 : i.spanMarker.Trailer = base.MakeTrailer(base.InternalKeySeqNumMax, i.span.Keys[0].Kind())
961 1 :
962 1 : // Truncate the key we return to our lower bound if we have one. Note that
963 1 : // we use the lowerBound function parameter, not i.lower. The lowerBound
964 1 : // argument is guaranteed to be ≥ i.lower. It may be equal to the SetBounds
965 1 : // lower bound, or it could come from a SeekGE or SeekPrefixGE search key.
966 1 : if lowerBound != nil && i.cmp(lowerBound, i.startKey()) > 0 {
967 1 : // Truncating to the lower bound may violate the upper bound if
968 1 : // lowerBound == i.upper. For example, a SeekGE(k) uses k as a lower
969 1 : // bound for truncating a span. The span a-z will be truncated to [k,
970 1 : // z). If i.upper == k, we'd mistakenly try to return a span [k, k), an
971 1 : // invariant violation.
972 1 : if i.comparer.Equal(lowerBound, i.upper) {
973 1 : return i.yieldNil()
974 1 : }
975 :
976 : // If the lowerBound argument came from a SeekGE or SeekPrefixGE
977 : // call, and it may be backed by a user-provided byte slice that is not
978 : // guaranteed to be stable.
979 : //
980 : // If the lowerBound argument is the lower bound set by SetBounds,
981 : // Pebble owns the slice's memory. However, consider two successive
982 : // calls to SetBounds(). The second may overwrite the lower bound.
983 : // Although the external contract requires a seek after a SetBounds,
984 : // Pebble's tests don't always. For this reason and to simplify
985 : // reasoning around lifetimes, always copy the bound into keyBuf when
986 : // truncating.
987 1 : i.keyBuf = append(i.keyBuf[:0], lowerBound...)
988 1 : i.spanMarker.UserKey = i.keyBuf
989 1 : i.spanMarkerTruncated = true
990 : }
991 1 : i.maybeUpdateMask()
992 1 : return i.verify(&i.spanMarker, base.LazyValue{})
993 : }
994 :
995 1 : func (i *InterleavingIter) disablePrefixMode() {
996 1 : if i.prefix != nil {
997 1 : i.prefix = nil
998 1 : // Clear the existing span. It may not hold the true end bound of the
999 1 : // underlying span.
1000 1 : i.span = nil
1001 1 : }
1002 : }
1003 :
1004 : func (i *InterleavingIter) verify(
1005 : k *base.InternalKey, v base.LazyValue,
1006 1 : ) (*base.InternalKey, base.LazyValue) {
1007 1 : // Wrap the entire function body in the invariants build tag, so that
1008 1 : // production builds elide this entire function.
1009 1 : if invariants.Enabled {
1010 1 : switch {
1011 0 : case i.dir == -1 && i.spanMarkerTruncated:
1012 0 : panic("pebble: invariant violation: truncated span key in reverse iteration")
1013 0 : case k != nil && i.lower != nil && i.cmp(k.UserKey, i.lower) < 0:
1014 0 : panic("pebble: invariant violation: key < lower bound")
1015 0 : case k != nil && i.upper != nil && i.cmp(k.UserKey, i.upper) >= 0:
1016 0 : panic("pebble: invariant violation: key ≥ upper bound")
1017 0 : case i.err != nil && k != nil:
1018 0 : panic("pebble: invariant violation: accumulated error swallowed")
1019 0 : case i.err == nil && i.pointIter.Error() != nil:
1020 0 : panic("pebble: invariant violation: pointIter swallowed")
1021 : }
1022 : }
1023 1 : return k, v
1024 : }
1025 :
1026 1 : func (i *InterleavingIter) savedKeyspan() {
1027 1 : i.spanMarkerTruncated = false
1028 1 : i.maskSpanChangedCalled = false
1029 1 : }
1030 :
1031 : // updateMask updates the current mask, if a mask is configured and the mask
1032 : // hasn't been updated with the current keyspan yet.
1033 1 : func (i *InterleavingIter) maybeUpdateMask() {
1034 1 : switch {
1035 1 : case i.mask == nil, i.maskSpanChangedCalled:
1036 1 : return
1037 1 : case !i.withinSpan || i.span.Empty():
1038 1 : i.clearMask()
1039 1 : case i.truncated:
1040 1 : i.mask.SpanChanged(&i.truncatedSpan)
1041 1 : i.maskSpanChangedCalled = true
1042 1 : default:
1043 1 : i.mask.SpanChanged(i.span)
1044 1 : i.maskSpanChangedCalled = true
1045 : }
1046 : }
1047 :
1048 : // clearMask clears the current mask, if a mask is configured and no mask should
1049 : // be active.
1050 1 : func (i *InterleavingIter) clearMask() {
1051 1 : if i.mask != nil {
1052 1 : i.maskSpanChangedCalled = false
1053 1 : i.mask.SpanChanged(nil)
1054 1 : }
1055 : }
1056 :
1057 1 : func (i *InterleavingIter) startKey() []byte {
1058 1 : if i.truncated {
1059 1 : return i.truncatedSpan.Start
1060 1 : }
1061 1 : return i.span.Start
1062 : }
1063 :
1064 1 : func (i *InterleavingIter) savePoint(key *base.InternalKey, value base.LazyValue) {
1065 1 : i.pointKey, i.pointVal = key, value
1066 1 : if key == nil {
1067 1 : i.err = firstError(i.err, i.pointIter.Error())
1068 1 : }
1069 1 : if invariants.Enabled {
1070 1 : if err := i.pointIter.Error(); key != nil && err != nil {
1071 0 : panic(errors.WithSecondaryError(
1072 0 : errors.AssertionFailedf("pebble: %T point iterator returned non-nil key %q while iter has error", i.pointIter, key),
1073 0 : err))
1074 : }
1075 : }
1076 : }
1077 :
1078 : // Span returns the span covering the last key returned, if any. A span key is
1079 : // considered to 'cover' a key if the key falls within the span's user key
1080 : // bounds. The returned span is owned by the InterleavingIter. The caller is
1081 : // responsible for copying if stability is required.
1082 : //
1083 : // Span will never return an invalid or empty span.
1084 1 : func (i *InterleavingIter) Span() *Span {
1085 1 : if !i.withinSpan || len(i.span.Keys) == 0 {
1086 1 : return nil
1087 1 : } else if i.truncated {
1088 1 : return &i.truncatedSpan
1089 1 : }
1090 1 : return i.span
1091 : }
1092 :
1093 : // SetBounds implements (base.InternalIterator).SetBounds.
1094 1 : func (i *InterleavingIter) SetBounds(lower, upper []byte) {
1095 1 : i.lower, i.upper = lower, upper
1096 1 : i.pointIter.SetBounds(lower, upper)
1097 1 : i.Invalidate()
1098 1 : }
1099 :
1100 : // SetContext implements (base.InternalIterator).SetContext.
1101 0 : func (i *InterleavingIter) SetContext(ctx context.Context) {
1102 0 : i.pointIter.SetContext(ctx)
1103 0 : }
1104 :
1105 : // Invalidate invalidates the interleaving iterator's current position, clearing
1106 : // its state. This prevents optimizations such as reusing the current span on
1107 : // seek.
1108 1 : func (i *InterleavingIter) Invalidate() {
1109 1 : i.span = nil
1110 1 : i.pointKey = nil
1111 1 : i.pointVal = base.LazyValue{}
1112 1 : }
1113 :
1114 : // Error implements (base.InternalIterator).Error.
1115 1 : func (i *InterleavingIter) Error() error {
1116 1 : return i.err
1117 1 : }
1118 :
1119 : // Close implements (base.InternalIterator).Close.
1120 1 : func (i *InterleavingIter) Close() error {
1121 1 : perr := i.pointIter.Close()
1122 1 : rerr := i.keyspanIter.Close()
1123 1 : return firstError(perr, rerr)
1124 1 : }
1125 :
1126 : // String implements (base.InternalIterator).String.
1127 0 : func (i *InterleavingIter) String() string {
1128 0 : return fmt.Sprintf("keyspan-interleaving(%q)", i.pointIter.String())
1129 0 : }
1130 :
1131 1 : func firstError(err0, err1 error) error {
1132 1 : if err0 != nil {
1133 1 : return err0
1134 1 : }
1135 1 : return err1
1136 : }
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