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 : // When InterleavingIterOpts.InterleaveEndKeys is set, in addition to
91 : // interleaving start keys, the interleaving iterator will interleave end
92 : // boundary keys (also at the maximumal sequence number). At these end boundary
93 : // positions, Span() will return the span to which the end boundary belongs.
94 : //
95 : // # SpanMask
96 : //
97 : // InterelavingIter takes a SpanMask parameter that may be used to configure the
98 : // behavior of the iterator. See the documentation on the SpanMask type.
99 : //
100 : // All spans containing keys are exposed during iteration.
101 : type InterleavingIter struct {
102 : cmp base.Compare
103 : comparer *base.Comparer
104 : pointIter base.InternalIterator
105 : keyspanIter FragmentIterator
106 : opts InterleavingIterOpts
107 : // keyBuf is used to copy SeekGE or SeekPrefixGE arguments when they're used
108 : // to truncate a span. The byte slices backing a SeekGE/SeekPrefixGE search
109 : // keys can come directly from the end user, so they're copied into keyBuf
110 : // to ensure key stability.
111 : keyBuf []byte
112 : // nextPrefixBuf is used during SeekPrefixGE calls to store the truncated
113 : // upper bound of the returned spans. SeekPrefixGE truncates the returned
114 : // spans to an upper bound of the seeked prefix's immediate successor.
115 : nextPrefixBuf []byte
116 : pointKV *base.InternalKV
117 : // err holds an iterator error from either pointIter or keyspanIter. It's
118 : // reset to nil on seeks. An overview of error-handling mechanics:
119 : //
120 : // Whenever either pointIter or keyspanIter is respositioned and a nil
121 : // key/span is returned, the code performing the positioning is responsible
122 : // for checking the iterator's Error() value. This happens in savePoint and
123 : // saveSpan[Forward,Backward].
124 : //
125 : // Once i.err is non-nil, the computation of i.pos must set i.pos =
126 : // posExhausted. This happens in compute[Smallest|Largest]Pos and
127 : // [next|prev]Pos. Setting i.pos to posExhausted ensures we'll yield nil to
128 : // the caller, which they'll interpret as a signal they must check Error().
129 : //
130 : // INVARIANTS:
131 : // i.err != nil => i.pos = posExhausted
132 : err error
133 : // prefix records the iterator's current prefix if the iterator is in prefix
134 : // mode. During prefix mode, Pebble will truncate spans to the next prefix.
135 : // If the iterator subsequently leaves prefix mode, the existing span cached
136 : // in i.span must be invalidated because its bounds do not reflect the
137 : // original span's true bounds.
138 : prefix []byte
139 : // span holds the span at the keyspanIter's current position. If the span is
140 : // wholly contained within the iterator bounds, this span is directly
141 : // returned to the iterator consumer through Span(). If either bound needed
142 : // to be truncated to the iterator bounds, then truncated is set to true and
143 : // Span() must return a pointer to truncatedSpan.
144 : span *Span
145 : // spanMarker holds the synthetic key that is returned when the iterator
146 : // passes over a key span's start bound.
147 : spanMarker base.InternalKV
148 : // truncated indicates whether or not the span at the current position
149 : // needed to be truncated. If it did, truncatedSpan holds the truncated
150 : // span that should be returned.
151 : truncatedSpan Span
152 : truncated bool
153 :
154 : // Keeping all of the bools/uint8s together reduces the sizeof the struct.
155 :
156 : // pos encodes the current position of the iterator: exhausted, on the point
157 : // key, on a keyspan start, or on a keyspan end.
158 : pos interleavePos
159 : // withinSpan indicates whether the iterator is currently positioned within
160 : // the bounds of the current span (i.span). withinSpan must be updated
161 : // whenever the interleaving iterator's position enters or exits the bounds
162 : // of a span.
163 : withinSpan bool
164 : // spanMarkerTruncated is set by SeekGE/SeekPrefixGE calls that truncate a
165 : // span's start bound marker to the search key. It's returned to false on
166 : // the next repositioning of the keyspan iterator.
167 : spanMarkerTruncated bool
168 : // maskSpanChangedCalled records whether or not the last call to
169 : // SpanMask.SpanChanged provided the current span (i.span) or not.
170 : maskSpanChangedCalled bool
171 : // dir indicates the direction of iteration: forward (+1) or backward (-1)
172 : dir int8
173 : }
174 :
175 : // interleavePos indicates the iterator's current position. Note that both
176 : // keyspanStart and keyspanEnd positions correspond to their user key boundaries
177 : // with maximal sequence numbers. This means in the forward direction
178 : // posKeyspanStart and posKeyspanEnd are always interleaved before a posPointKey
179 : // with the same user key.
180 : type interleavePos int8
181 :
182 : const (
183 : posUninitialized interleavePos = iota
184 : posExhausted
185 : posPointKey
186 : posKeyspanStart
187 : posKeyspanEnd
188 : )
189 :
190 : // Assert that *InterleavingIter implements the InternalIterator interface.
191 : var _ base.InternalIterator = &InterleavingIter{}
192 :
193 : // InterleavingIterOpts holds options configuring the behavior of a
194 : // InterleavingIter.
195 : type InterleavingIterOpts struct {
196 : Mask SpanMask
197 : LowerBound, UpperBound []byte
198 : // InterleaveEndKeys configures the interleaving iterator to interleave the
199 : // end keys of spans (in addition to the start keys, which are always
200 : // interleaved).
201 : InterleaveEndKeys bool
202 : }
203 :
204 : // Init initializes the InterleavingIter to interleave point keys from pointIter
205 : // with key spans from keyspanIter.
206 : //
207 : // The point iterator must already have the bounds provided on opts. Init does
208 : // not propagate the bounds down the iterator stack.
209 : func (i *InterleavingIter) Init(
210 : comparer *base.Comparer,
211 : pointIter base.InternalIterator,
212 : keyspanIter FragmentIterator,
213 : opts InterleavingIterOpts,
214 1 : ) {
215 1 : keyspanIter = MaybeAssert(keyspanIter, comparer.Compare)
216 1 : // To debug:
217 1 : // keyspanIter = InjectLogging(keyspanIter, base.DefaultLogger)
218 1 : *i = InterleavingIter{
219 1 : cmp: comparer.Compare,
220 1 : comparer: comparer,
221 1 : pointIter: pointIter,
222 1 : keyspanIter: keyspanIter,
223 1 : opts: opts,
224 1 : }
225 1 : }
226 :
227 : // InitSeekGE may be called after Init but before any positioning method.
228 : // InitSeekGE initializes the current position of the point iterator and then
229 : // performs a SeekGE on the keyspan iterator using the provided key. InitSeekGE
230 : // returns whichever point or keyspan key is smaller. After InitSeekGE, the
231 : // iterator is positioned and may be repositioned using relative positioning
232 : // methods.
233 : //
234 : // This method is used specifically for lazily constructing combined iterators.
235 : // It allows for seeding the iterator with the current position of the point
236 : // iterator.
237 : func (i *InterleavingIter) InitSeekGE(
238 : prefix, key []byte, pointKV *base.InternalKV,
239 1 : ) *base.InternalKV {
240 1 : i.dir = +1
241 1 : i.clearMask()
242 1 : i.prefix = prefix
243 1 : i.savePoint(pointKV)
244 1 : // NB: This keyspanSeekGE call will truncate the span to the seek key if
245 1 : // necessary. This truncation is important for cases where a switch to
246 1 : // combined iteration is made during a user-initiated SeekGE.
247 1 : i.keyspanSeekGE(key, prefix)
248 1 : i.computeSmallestPos()
249 1 : return i.yieldPosition(key, i.nextPos)
250 1 : }
251 :
252 : // InitSeekLT may be called after Init but before any positioning method.
253 : // InitSeekLT initializes the current position of the point iterator and then
254 : // performs a SeekLT on the keyspan iterator using the provided key. InitSeekLT
255 : // returns whichever point or keyspan key is larger. After InitSeekLT, the
256 : // iterator is positioned and may be repositioned using relative positioning
257 : // methods.
258 : //
259 : // This method is used specifically for lazily constructing combined iterators.
260 : // It allows for seeding the iterator with the current position of the point
261 : // iterator.
262 1 : func (i *InterleavingIter) InitSeekLT(key []byte, pointKV *base.InternalKV) *base.InternalKV {
263 1 : i.dir = -1
264 1 : i.clearMask()
265 1 : i.savePoint(pointKV)
266 1 : i.keyspanSeekLT(key)
267 1 : i.computeLargestPos()
268 1 : return i.yieldPosition(i.opts.LowerBound, i.prevPos)
269 1 : }
270 :
271 : // SeekGE implements (base.InternalIterator).SeekGE.
272 : //
273 : // If there exists a span with a start key ≤ the first matching point key,
274 : // SeekGE will return a synthetic span marker key for the span. If this span's
275 : // start key is less than key, the returned marker will be truncated to key.
276 : // Note that this search-key truncation of the marker's key is not applied to
277 : // the span returned by Span.
278 : //
279 : // NB: In accordance with the base.InternalIterator contract:
280 : //
281 : // i.lower ≤ key
282 1 : func (i *InterleavingIter) SeekGE(key []byte, flags base.SeekGEFlags) *base.InternalKV {
283 1 : i.err = nil
284 1 : i.clearMask()
285 1 : i.disablePrefixMode()
286 1 : i.savePoint(i.pointIter.SeekGE(key, flags))
287 1 :
288 1 : // We need to seek the keyspan iterator too. If the keyspan iterator was
289 1 : // already positioned at a span, we might be able to avoid the seek if the
290 1 : // seek key falls within the existing span's bounds.
291 1 : if i.span != nil && i.cmp(key, i.span.End) < 0 && i.cmp(key, i.span.Start) >= 0 {
292 1 : // We're seeking within the existing span's bounds. We still might need
293 1 : // truncate the span to the iterator's bounds.
294 1 : i.saveSpanForward(i.span, nil)
295 1 : i.savedKeyspan()
296 1 : } else {
297 1 : i.keyspanSeekGE(key, nil /* prefix */)
298 1 : }
299 :
300 1 : i.dir = +1
301 1 : i.computeSmallestPos()
302 1 : return i.yieldPosition(key, i.nextPos)
303 : }
304 :
305 : // SeekPrefixGE implements (base.InternalIterator).SeekPrefixGE.
306 : //
307 : // If there exists a span with a start key ≤ the first matching point key,
308 : // SeekPrefixGE will return a synthetic span marker key for the span. If this
309 : // span's start key is less than key, the returned marker will be truncated to
310 : // key. Note that this search-key truncation of the marker's key is not applied
311 : // to the span returned by Span.
312 : //
313 : // NB: In accordance with the base.InternalIterator contract:
314 : //
315 : // i.lower ≤ key
316 : func (i *InterleavingIter) SeekPrefixGE(
317 : prefix, key []byte, flags base.SeekGEFlags,
318 1 : ) *base.InternalKV {
319 1 : i.err = nil
320 1 : i.clearMask()
321 1 : i.prefix = prefix
322 1 : i.savePoint(i.pointIter.SeekPrefixGE(prefix, key, flags))
323 1 :
324 1 : // We need to seek the keyspan iterator too. If the keyspan iterator was
325 1 : // already positioned at a span, we might be able to avoid the seek if the
326 1 : // entire seek prefix key falls within the existing span's bounds.
327 1 : //
328 1 : // During a SeekPrefixGE, Pebble defragments range keys within the bounds of
329 1 : // the prefix. For example, a SeekPrefixGE('c', 'c@8') must defragment the
330 1 : // any overlapping range keys within the bounds of [c,c\00).
331 1 : //
332 1 : // If range keys are fragmented within a prefix (eg, because a version
333 1 : // within a prefix was chosen as an sstable boundary), then it's possible
334 1 : // the seek key falls into the current i.span, but the current i.span does
335 1 : // not wholly cover the seek prefix.
336 1 : //
337 1 : // For example, a SeekPrefixGE('d@5') may only defragment a range key to
338 1 : // the bounds of [c@2,e). A subsequent SeekPrefixGE('c@0') must re-seek the
339 1 : // keyspan iterator, because although 'c@0' is contained within [c@2,e), the
340 1 : // full span of the prefix is not.
341 1 : //
342 1 : // Similarly, a SeekPrefixGE('a@3') may only defragment a range key to the
343 1 : // bounds [a,c@8). A subsequent SeekPrefixGE('c@10') must re-seek the
344 1 : // keyspan iterator, because although 'c@10' is contained within [a,c@8),
345 1 : // the full span of the prefix is not.
346 1 : seekKeyspanIter := true
347 1 : if i.span != nil && i.cmp(prefix, i.span.Start) >= 0 {
348 1 : if ei := i.comparer.Split(i.span.End); i.cmp(prefix, i.span.End[:ei]) < 0 {
349 1 : // We're seeking within the existing span's bounds. We still might need
350 1 : // truncate the span to the iterator's bounds.
351 1 : i.saveSpanForward(i.span, nil)
352 1 : i.savedKeyspan()
353 1 : seekKeyspanIter = false
354 1 : }
355 : }
356 1 : if seekKeyspanIter {
357 1 : i.keyspanSeekGE(key, prefix)
358 1 : }
359 :
360 1 : i.dir = +1
361 1 : i.computeSmallestPos()
362 1 : return i.yieldPosition(key, i.nextPos)
363 : }
364 :
365 : // SeekLT implements (base.InternalIterator).SeekLT.
366 1 : func (i *InterleavingIter) SeekLT(key []byte, flags base.SeekLTFlags) *base.InternalKV {
367 1 : i.err = nil
368 1 : i.clearMask()
369 1 : i.disablePrefixMode()
370 1 : i.savePoint(i.pointIter.SeekLT(key, flags))
371 1 :
372 1 : // We need to seek the keyspan iterator too. If the keyspan iterator was
373 1 : // already positioned at a span, we might be able to avoid the seek if the
374 1 : // seek key falls within the existing span's bounds.
375 1 : if i.span != nil && i.cmp(key, i.span.Start) > 0 && i.cmp(key, i.span.End) < 0 {
376 1 : // We're seeking within the existing span's bounds. We still might need
377 1 : // truncate the span to the iterator's bounds.
378 1 : i.saveSpanBackward(i.span, nil)
379 1 : // The span's start key is still not guaranteed to be less than key,
380 1 : // because of the bounds enforcement. Consider the following example:
381 1 : //
382 1 : // Bounds are set to [d,e). The user performs a SeekLT(d). The
383 1 : // FragmentIterator.SeekLT lands on a span [b,f). This span has a start
384 1 : // key less than d, as expected. Above, saveSpanBackward truncates the
385 1 : // span to match the iterator's current bounds, modifying the span to
386 1 : // [d,e), which does not overlap the search space of [-∞, d).
387 1 : //
388 1 : // This problem is a consequence of the SeekLT's exclusive search key
389 1 : // and the fact that we don't perform bounds truncation at every leaf
390 1 : // iterator.
391 1 : if i.span != nil && i.truncated && i.cmp(i.truncatedSpan.Start, key) >= 0 {
392 1 : i.span = nil
393 1 : }
394 1 : i.savedKeyspan()
395 1 : } else {
396 1 : i.keyspanSeekLT(key)
397 1 : }
398 :
399 1 : i.dir = -1
400 1 : i.computeLargestPos()
401 1 : return i.yieldPosition(i.opts.LowerBound, i.prevPos)
402 : }
403 :
404 : // First implements (base.InternalIterator).First.
405 1 : func (i *InterleavingIter) First() *base.InternalKV {
406 1 : i.err = nil
407 1 : i.clearMask()
408 1 : i.disablePrefixMode()
409 1 : i.savePoint(i.pointIter.First())
410 1 : i.saveSpanForward(i.keyspanIter.First())
411 1 : i.savedKeyspan()
412 1 : i.dir = +1
413 1 : i.computeSmallestPos()
414 1 : return i.yieldPosition(i.opts.LowerBound, i.nextPos)
415 1 : }
416 :
417 : // Last implements (base.InternalIterator).Last.
418 1 : func (i *InterleavingIter) Last() *base.InternalKV {
419 1 : i.err = nil
420 1 : i.clearMask()
421 1 : i.disablePrefixMode()
422 1 : i.savePoint(i.pointIter.Last())
423 1 : i.saveSpanBackward(i.keyspanIter.Last())
424 1 : i.savedKeyspan()
425 1 : i.dir = -1
426 1 : i.computeLargestPos()
427 1 : return i.yieldPosition(i.opts.LowerBound, i.prevPos)
428 1 : }
429 :
430 : // Next implements (base.InternalIterator).Next.
431 1 : func (i *InterleavingIter) Next() *base.InternalKV {
432 1 : if i.dir == -1 {
433 1 : // Switching directions.
434 1 : i.dir = +1
435 1 :
436 1 : if i.opts.Mask != nil {
437 1 : // Clear the mask while we reposition the point iterator. While
438 1 : // switching directions, we may move the point iterator outside of
439 1 : // i.span's bounds.
440 1 : i.clearMask()
441 1 : }
442 :
443 : // When switching directions, iterator state corresponding to the
444 : // current iterator position (as indicated by i.pos) is already correct.
445 : // However any state that has yet to be interleaved describes a position
446 : // behind the current iterator position and needs to be updated to
447 : // describe the position ahead of the current iterator position.
448 1 : switch i.pos {
449 0 : case posExhausted:
450 : // Nothing to do. The below nextPos call will move both the point
451 : // key and span to their next positions and return
452 : // MIN(point,s.Start).
453 1 : case posPointKey:
454 1 : // If we're currently on a point key, the below nextPos will
455 1 : // correctly Next the point key iterator to the next point key.
456 1 : // Do we need to move the span forwards? If the current span lies
457 1 : // entirely behind the current key (!i.withinSpan), then we
458 1 : // need to move it to the first span in the forward direction.
459 1 : if !i.withinSpan {
460 1 : i.saveSpanForward(i.keyspanIter.Next())
461 1 : i.savedKeyspan()
462 1 : }
463 1 : case posKeyspanStart:
464 1 : i.withinSpan = true
465 1 : // Since we're positioned on a Span, the pointIter is positioned
466 1 : // entirely behind the current iterator position. Reposition it
467 1 : // ahead of the current iterator position.
468 1 : i.switchPointIteratorIntoForward()
469 1 : case posKeyspanEnd:
470 1 : // Since we're positioned on a Span, the pointIter is positioned
471 1 : // entirely behind of the current iterator position. Reposition it
472 1 : // ahead the current iterator position.
473 1 : i.switchPointIteratorIntoForward()
474 : }
475 : // Fallthrough to calling i.nextPos.
476 : }
477 1 : i.nextPos()
478 1 : return i.yieldPosition(i.opts.LowerBound, i.nextPos)
479 : }
480 :
481 : // NextPrefix implements (base.InternalIterator).NextPrefix.
482 : //
483 : // Calling NextPrefix while positioned at a span boundary is prohibited.
484 1 : func (i *InterleavingIter) NextPrefix(succKey []byte) *base.InternalKV {
485 1 : if i.dir == -1 {
486 0 : panic("pebble: cannot switch directions with NextPrefix")
487 : }
488 :
489 1 : switch i.pos {
490 0 : case posExhausted:
491 0 : return nil
492 1 : case posPointKey:
493 1 : i.savePoint(i.pointIter.NextPrefix(succKey))
494 1 : if i.withinSpan {
495 1 : if i.pointKV == nil || i.cmp(i.span.End, i.pointKV.K.UserKey) <= 0 {
496 1 : i.pos = posKeyspanEnd
497 1 : } else {
498 1 : i.pos = posPointKey
499 1 : }
500 1 : } else {
501 1 : i.computeSmallestPos()
502 1 : }
503 0 : case posKeyspanStart, posKeyspanEnd:
504 0 : panic(errors.AssertionFailedf("NextPrefix called while positioned on a span boundary"))
505 : }
506 1 : return i.yieldPosition(i.opts.LowerBound, i.nextPos)
507 : }
508 :
509 : // Prev implements (base.InternalIterator).Prev.
510 1 : func (i *InterleavingIter) Prev() *base.InternalKV {
511 1 : if i.dir == +1 {
512 1 : // Switching directions.
513 1 : i.dir = -1
514 1 :
515 1 : if i.opts.Mask != nil {
516 1 : // Clear the mask while we reposition the point iterator. While
517 1 : // switching directions, we may move the point iterator outside of
518 1 : // i.span's bounds.
519 1 : i.clearMask()
520 1 : }
521 :
522 : // When switching directions, iterator state corresponding to the
523 : // current iterator position (as indicated by i.pos) is already correct.
524 : // However any state that has yet to be interleaved describes a position
525 : // ahead of the current iterator position and needs to be updated to
526 : // describe the position behind the current iterator position.
527 1 : switch i.pos {
528 0 : case posExhausted:
529 : // Nothing to do. The below prevPos call will move both the point
530 : // key and span to previous positions and return MAX(point, s.End).
531 1 : case posPointKey:
532 1 : // If we're currently on a point key, the point iterator is in the
533 1 : // right place and the call to prevPos will correctly Prev the point
534 1 : // key iterator to the previous point key. Do we need to move the
535 1 : // span backwards? If the current span lies entirely ahead of the
536 1 : // current key (!i.withinSpan), then we need to move it to the first
537 1 : // span in the reverse direction.
538 1 : if !i.withinSpan {
539 1 : i.saveSpanBackward(i.keyspanIter.Prev())
540 1 : i.savedKeyspan()
541 1 : }
542 1 : case posKeyspanStart:
543 1 : // Since we're positioned on a Span, the pointIter is positioned
544 1 : // entirely ahead of the current iterator position. Reposition it
545 1 : // behind the current iterator position.
546 1 : i.switchPointIteratorIntoReverse()
547 1 : // Without considering truncation of spans to seek keys, the keyspan
548 1 : // iterator is already in the right place. But consider span [a, z)
549 1 : // and this sequence of iterator calls:
550 1 : //
551 1 : // SeekGE('c') = c.RANGEKEYSET#72057594037927935
552 1 : // Prev() = a.RANGEKEYSET#72057594037927935
553 1 : //
554 1 : // If the current span's start key was last surfaced truncated due
555 1 : // to a SeekGE or SeekPrefixGE call, then it's still relevant in the
556 1 : // reverse direction with an untruncated start key.
557 1 : if i.spanMarkerTruncated {
558 1 : // When we fallthrough to calling prevPos, we want to move to
559 1 : // MAX(point, span.Start). We cheat here by claiming we're
560 1 : // currently on the end boundary, so that we'll move on to the
561 1 : // untruncated start key if necessary.
562 1 : i.pos = posKeyspanEnd
563 1 : }
564 1 : case posKeyspanEnd:
565 1 : // Since we're positioned on a Span, the pointIter is positioned
566 1 : // entirely ahead of the current iterator position. Reposition it
567 1 : // behind the current iterator position.
568 1 : i.switchPointIteratorIntoReverse()
569 : }
570 :
571 1 : if i.spanMarkerTruncated {
572 1 : // Save the keyspan again to clear truncation.
573 1 : i.savedKeyspan()
574 1 : }
575 : // Fallthrough to calling i.prevPos.
576 : }
577 1 : i.prevPos()
578 1 : return i.yieldPosition(i.opts.LowerBound, i.prevPos)
579 : }
580 :
581 : // computeSmallestPos sets i.{pos,withinSpan} to:
582 : //
583 : // MIN(i.pointKey, i.span.Start)
584 1 : func (i *InterleavingIter) computeSmallestPos() {
585 1 : if i.err == nil {
586 1 : if i.span != nil && (i.pointKV == nil || i.cmp(i.startKey(), i.pointKV.K.UserKey) <= 0) {
587 1 : i.withinSpan = true
588 1 : i.pos = posKeyspanStart
589 1 : return
590 1 : }
591 1 : i.withinSpan = false
592 1 : if i.pointKV != nil {
593 1 : i.pos = posPointKey
594 1 : return
595 1 : }
596 : }
597 1 : i.pos = posExhausted
598 : }
599 :
600 : // computeLargestPos sets i.{pos,withinSpan} to:
601 : //
602 : // MAX(i.pointKey, i.span.End)
603 1 : func (i *InterleavingIter) computeLargestPos() {
604 1 : if i.err == nil {
605 1 : if i.span != nil && (i.pointKV == nil || i.cmp(i.span.End, i.pointKV.K.UserKey) > 0) {
606 1 : i.withinSpan = true
607 1 : i.pos = posKeyspanEnd
608 1 : return
609 1 : }
610 1 : i.withinSpan = false
611 1 : if i.pointKV != nil {
612 1 : i.pos = posPointKey
613 1 : return
614 1 : }
615 : }
616 1 : i.pos = posExhausted
617 : }
618 :
619 : // nextPos advances the iterator one position in the forward direction.
620 1 : func (i *InterleavingIter) nextPos() {
621 1 : if invariants.Enabled {
622 1 : defer func() {
623 1 : if i.err != nil && i.pos != posExhausted {
624 0 : panic(errors.AssertionFailedf("iterator has accumulated error but i.pos = %d", i.pos))
625 : }
626 : }()
627 : }
628 : // NB: If i.err != nil or any of the positioning methods performed in this
629 : // function result in i.err != nil, we must set i.pos = posExhausted. We
630 : // perform this check explicitly here, but if any of the branches below
631 : // advance either iterator, they must also check i.err and set posExhausted
632 : // if necessary.
633 1 : if i.err != nil {
634 0 : i.pos = posExhausted
635 0 : return
636 0 : }
637 :
638 1 : switch i.pos {
639 0 : case posExhausted:
640 0 : i.switchPointIteratorIntoForward()
641 0 : i.saveSpanForward(i.keyspanIter.Next())
642 0 : i.savedKeyspan()
643 0 : i.computeSmallestPos()
644 1 : case posPointKey:
645 1 : i.savePoint(i.pointIter.Next())
646 1 : if i.err != nil {
647 0 : i.pos = posExhausted
648 0 : return
649 0 : }
650 : // If we're not currently within the span, we want to chose the
651 : // MIN(pointKey,span.Start), which is exactly the calculation performed
652 : // by computeSmallestPos.
653 1 : if !i.withinSpan {
654 1 : i.computeSmallestPos()
655 1 : return
656 1 : }
657 : // i.withinSpan=true
658 : // Since we previously were within the span, we want to choose the
659 : // MIN(pointKey,span.End).
660 1 : switch {
661 0 : case i.span == nil:
662 0 : panic("i.withinSpan=true and i.span=nil")
663 1 : case i.pointKV == nil:
664 1 : // Since i.withinSpan=true, we step onto the end boundary of the
665 1 : // keyspan.
666 1 : i.pos = posKeyspanEnd
667 1 : default:
668 1 : // i.withinSpan && i.pointKV != nil && i.span != nil
669 1 : if i.cmp(i.span.End, i.pointKV.K.UserKey) <= 0 {
670 1 : i.pos = posKeyspanEnd
671 1 : } else {
672 1 : i.pos = posPointKey
673 1 : }
674 : }
675 1 : case posKeyspanStart:
676 1 : // Either a point key or the span's end key comes next.
677 1 : if i.pointKV != nil && i.cmp(i.pointKV.K.UserKey, i.span.End) < 0 {
678 1 : i.pos = posPointKey
679 1 : } else {
680 1 : i.pos = posKeyspanEnd
681 1 : }
682 1 : case posKeyspanEnd:
683 1 : i.saveSpanForward(i.keyspanIter.Next())
684 1 : i.savedKeyspan()
685 1 : i.computeSmallestPos()
686 0 : default:
687 0 : panic(fmt.Sprintf("unexpected pos=%d", i.pos))
688 : }
689 : }
690 :
691 : // prevPos advances the iterator one position in the reverse direction.
692 1 : func (i *InterleavingIter) prevPos() {
693 1 : if invariants.Enabled {
694 1 : defer func() {
695 1 : if i.err != nil && i.pos != posExhausted {
696 0 : panic(errors.AssertionFailedf("iterator has accumulated error but i.pos = %d", i.pos))
697 : }
698 : }()
699 : }
700 : // NB: If i.err != nil or any of the positioning methods performed in this
701 : // function result in i.err != nil, we must set i.pos = posExhausted. We
702 : // perform this check explicitly here, but if any of the branches below
703 : // advance either iterator, they must also check i.err and set posExhausted
704 : // if necessary.
705 1 : if i.err != nil {
706 0 : i.pos = posExhausted
707 0 : return
708 0 : }
709 :
710 1 : switch i.pos {
711 0 : case posExhausted:
712 0 : i.switchPointIteratorIntoReverse()
713 0 : i.saveSpanBackward(i.keyspanIter.Prev())
714 0 : i.savedKeyspan()
715 0 : i.computeLargestPos()
716 1 : case posPointKey:
717 1 : i.savePoint(i.pointIter.Prev())
718 1 : if i.err != nil {
719 0 : i.pos = posExhausted
720 0 : return
721 0 : }
722 : // If we're not currently covered by the span, we want to chose the
723 : // MAX(pointKey,span.End), which is exactly the calculation performed
724 : // by computeLargestPos.
725 1 : if !i.withinSpan {
726 1 : i.computeLargestPos()
727 1 : return
728 1 : }
729 1 : switch {
730 0 : case i.span == nil:
731 0 : panic("withinSpan=true, but i.span == nil")
732 1 : case i.pointKV == nil:
733 1 : i.pos = posKeyspanStart
734 1 : default:
735 1 : // i.withinSpan && i.pointKey != nil && i.span != nil
736 1 : if i.cmp(i.span.Start, i.pointKV.K.UserKey) > 0 {
737 1 : i.pos = posKeyspanStart
738 1 : } else {
739 1 : i.pos = posPointKey
740 1 : }
741 : }
742 1 : case posKeyspanStart:
743 1 : i.saveSpanBackward(i.keyspanIter.Prev())
744 1 : i.savedKeyspan()
745 1 : i.computeLargestPos()
746 1 : case posKeyspanEnd:
747 1 : // Either a point key or the span's start key is previous.
748 1 : if i.pointKV != nil && i.cmp(i.pointKV.K.UserKey, i.span.Start) >= 0 {
749 1 : i.pos = posPointKey
750 1 : } else {
751 1 : i.pos = posKeyspanStart
752 1 : }
753 0 : default:
754 0 : panic(fmt.Sprintf("unexpected pos=%d", i.pos))
755 : }
756 : }
757 :
758 1 : func (i *InterleavingIter) yieldPosition(lowerBound []byte, advance func()) *base.InternalKV {
759 1 : // This loop returns the first visible position in the current iteration
760 1 : // direction. Some positions are not visible and skipped. For example, if
761 1 : // masking is enabled and the iterator is positioned over a masked point
762 1 : // key, this loop skips the position. If a span's start key should be
763 1 : // interleaved next, but the span is empty, the loop continues to the next
764 1 : // key. Currently, span end keys are also always skipped, and are used only
765 1 : // for maintaining internal state.
766 1 : for {
767 1 : switch i.pos {
768 1 : case posExhausted:
769 1 : return i.yieldNil()
770 1 : case posPointKey:
771 1 : if i.pointKV == nil {
772 0 : panic("i.pointKV is nil")
773 : }
774 :
775 1 : if i.opts.Mask != nil {
776 1 : i.maybeUpdateMask()
777 1 : if i.withinSpan && i.opts.Mask.SkipPoint(i.pointKV.K.UserKey) {
778 1 : // The span covers the point key. If a SkipPoint hook is
779 1 : // configured, ask it if we should skip this point key.
780 1 : if i.prefix != nil {
781 1 : // During prefix-iteration node, once a point is masked,
782 1 : // all subsequent keys with the same prefix must also be
783 1 : // masked according to the key ordering. We can stop and
784 1 : // return nil.
785 1 : //
786 1 : // NB: The above is not just an optimization. During
787 1 : // prefix-iteration mode, the internal iterator contract
788 1 : // prohibits us from Next-ing beyond the first key
789 1 : // beyond the iteration prefix. If we didn't already
790 1 : // stop early, we would need to check if this masked
791 1 : // point is already beyond the prefix.
792 1 : return i.yieldNil()
793 1 : }
794 : // TODO(jackson): If we thread a base.Comparer through to
795 : // InterleavingIter so that we have access to
796 : // ImmediateSuccessor, we could use NextPrefix. We'd need to
797 : // tweak the SpanMask interface slightly.
798 :
799 : // Advance beyond the masked point key.
800 1 : advance()
801 1 : continue
802 : }
803 : }
804 1 : return i.yieldPointKey()
805 1 : case posKeyspanEnd:
806 1 : if !i.opts.InterleaveEndKeys {
807 1 : // Don't interleave end keys; just advance.
808 1 : advance()
809 1 : continue
810 : }
811 1 : return i.yieldSyntheticSpanEndMarker()
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.yieldSyntheticSpanStartMarker(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 : // switchPointIteratorIntoReverse switches the direction of the point iterator
852 : // into reverse, stepping to the previous point key. If the point iterator is
853 : // exhausted in the forward direction and there's an upper bound present, it's
854 : // re-seeked to ensure the iterator obeys the upper bound.
855 1 : func (i *InterleavingIter) switchPointIteratorIntoReverse() {
856 1 : if i.pointKV == nil && i.opts.UpperBound != nil {
857 1 : i.savePoint(i.pointIter.SeekLT(i.opts.UpperBound, base.SeekLTFlagsNone))
858 1 : return
859 1 : }
860 1 : i.savePoint(i.pointIter.Prev())
861 : }
862 :
863 : // switchPointIteratorIntoForward switches the direction of the point iterator
864 : // into the forward direction, stepping to the next point key. If the point
865 : // iterator is exhausted in the reverse direction and there's a lower bound
866 : // present, it's re-seeked to ensure the iterator obeys the lower bound.
867 1 : func (i *InterleavingIter) switchPointIteratorIntoForward() {
868 1 : if i.pointKV == nil && i.opts.LowerBound != nil {
869 1 : i.savePoint(i.pointIter.SeekGE(i.opts.LowerBound, base.SeekGEFlagsNone))
870 1 : return
871 1 : }
872 1 : i.savePoint(i.pointIter.Next())
873 : }
874 :
875 1 : func (i *InterleavingIter) saveSpanForward(span *Span, err error) {
876 1 : i.span = span
877 1 : i.err = firstError(i.err, err)
878 1 : i.truncated = false
879 1 : i.truncatedSpan = Span{}
880 1 : if i.span == nil {
881 1 : return
882 1 : }
883 : // Check the upper bound if we have one.
884 1 : if i.opts.UpperBound != nil && i.cmp(i.span.Start, i.opts.UpperBound) >= 0 {
885 1 : i.span = nil
886 1 : return
887 1 : }
888 :
889 : // TODO(jackson): The key comparisons below truncate bounds whenever the
890 : // keyspan iterator is repositioned. We could perform this lazily, and do it
891 : // the first time the user actually asks for this span's bounds in
892 : // SpanBounds. This would reduce work in the case where there's no span
893 : // covering the point and the keyspan iterator is non-empty.
894 :
895 : // NB: These truncations don't require setting `keyspanMarkerTruncated`:
896 : // That flag only applies to truncated span marker keys.
897 1 : if i.opts.LowerBound != nil && i.cmp(i.span.Start, i.opts.LowerBound) < 0 {
898 1 : i.truncated = true
899 1 : i.truncatedSpan = *i.span
900 1 : i.truncatedSpan.Start = i.opts.LowerBound
901 1 : }
902 1 : if i.opts.UpperBound != nil && i.cmp(i.opts.UpperBound, i.span.End) < 0 {
903 1 : if !i.truncated {
904 1 : i.truncated = true
905 1 : i.truncatedSpan = *i.span
906 1 : }
907 1 : i.truncatedSpan.End = i.opts.UpperBound
908 : }
909 : // If this is a part of a SeekPrefixGE call, we may also need to truncate to
910 : // the prefix's bounds.
911 1 : if i.prefix != nil {
912 1 : if !i.truncated {
913 1 : i.truncated = true
914 1 : i.truncatedSpan = *i.span
915 1 : }
916 1 : if i.cmp(i.prefix, i.truncatedSpan.Start) > 0 {
917 1 : i.truncatedSpan.Start = i.prefix
918 1 : }
919 1 : i.nextPrefixBuf = i.comparer.ImmediateSuccessor(i.nextPrefixBuf[:0], i.prefix)
920 1 : if i.truncated && i.cmp(i.nextPrefixBuf, i.truncatedSpan.End) < 0 {
921 1 : i.truncatedSpan.End = i.nextPrefixBuf
922 1 : }
923 : }
924 :
925 1 : if i.truncated && i.comparer.Equal(i.truncatedSpan.Start, i.truncatedSpan.End) {
926 1 : i.span = nil
927 1 : }
928 : }
929 :
930 1 : func (i *InterleavingIter) saveSpanBackward(span *Span, err error) {
931 1 : i.span = span
932 1 : i.err = firstError(i.err, err)
933 1 : i.truncated = false
934 1 : i.truncatedSpan = Span{}
935 1 : if i.span == nil {
936 1 : return
937 1 : }
938 :
939 : // Check the lower bound if we have one.
940 1 : if i.opts.LowerBound != nil && i.cmp(i.span.End, i.opts.LowerBound) <= 0 {
941 1 : i.span = nil
942 1 : return
943 1 : }
944 :
945 : // TODO(jackson): The key comparisons below truncate bounds whenever the
946 : // keyspan iterator is repositioned. We could perform this lazily, and do it
947 : // the first time the user actually asks for this span's bounds in
948 : // SpanBounds. This would reduce work in the case where there's no span
949 : // covering the point and the keyspan iterator is non-empty.
950 :
951 : // NB: These truncations don't require setting `keyspanMarkerTruncated`:
952 : // That flag only applies to truncated span marker keys.
953 1 : if i.opts.LowerBound != nil && i.cmp(i.span.Start, i.opts.LowerBound) < 0 {
954 1 : i.truncated = true
955 1 : i.truncatedSpan = *i.span
956 1 : i.truncatedSpan.Start = i.opts.LowerBound
957 1 : }
958 1 : if i.opts.UpperBound != nil && i.cmp(i.opts.UpperBound, i.span.End) < 0 {
959 1 : if !i.truncated {
960 1 : i.truncated = true
961 1 : i.truncatedSpan = *i.span
962 1 : }
963 1 : i.truncatedSpan.End = i.opts.UpperBound
964 : }
965 1 : if i.truncated && i.comparer.Equal(i.truncatedSpan.Start, i.truncatedSpan.End) {
966 1 : i.span = nil
967 1 : }
968 : }
969 :
970 1 : func (i *InterleavingIter) yieldNil() *base.InternalKV {
971 1 : i.withinSpan = false
972 1 : i.clearMask()
973 1 : return i.verify(nil)
974 1 : }
975 :
976 1 : func (i *InterleavingIter) yieldPointKey() *base.InternalKV {
977 1 : return i.verify(i.pointKV)
978 1 : }
979 :
980 1 : func (i *InterleavingIter) yieldSyntheticSpanStartMarker(lowerBound []byte) *base.InternalKV {
981 1 : i.spanMarker.K.UserKey = i.startKey()
982 1 : i.spanMarker.K.Trailer = base.MakeTrailer(base.InternalKeySeqNumMax, i.span.Keys[0].Kind())
983 1 :
984 1 : // Truncate the key we return to our lower bound if we have one. Note that
985 1 : // we use the lowerBound function parameter, not i.lower. The lowerBound
986 1 : // argument is guaranteed to be ≥ i.lower. It may be equal to the SetBounds
987 1 : // lower bound, or it could come from a SeekGE or SeekPrefixGE search key.
988 1 : if lowerBound != nil && i.cmp(lowerBound, i.startKey()) > 0 {
989 1 : // Truncating to the lower bound may violate the upper bound if
990 1 : // lowerBound == i.upper. For example, a SeekGE(k) uses k as a lower
991 1 : // bound for truncating a span. The span a-z will be truncated to [k,
992 1 : // z). If i.upper == k, we'd mistakenly try to return a span [k, k), an
993 1 : // invariant violation.
994 1 : if i.comparer.Equal(lowerBound, i.opts.UpperBound) {
995 1 : return i.yieldNil()
996 1 : }
997 :
998 : // If the lowerBound argument came from a SeekGE or SeekPrefixGE
999 : // call, and it may be backed by a user-provided byte slice that is not
1000 : // guaranteed to be stable.
1001 : //
1002 : // If the lowerBound argument is the lower bound set by SetBounds,
1003 : // Pebble owns the slice's memory. However, consider two successive
1004 : // calls to SetBounds(). The second may overwrite the lower bound.
1005 : // Although the external contract requires a seek after a SetBounds,
1006 : // Pebble's tests don't always. For this reason and to simplify
1007 : // reasoning around lifetimes, always copy the bound into keyBuf when
1008 : // truncating.
1009 1 : i.keyBuf = append(i.keyBuf[:0], lowerBound...)
1010 1 : i.spanMarker.K.UserKey = i.keyBuf
1011 1 : i.spanMarkerTruncated = true
1012 : }
1013 1 : i.maybeUpdateMask()
1014 1 : return i.verify(&i.spanMarker)
1015 : }
1016 :
1017 1 : func (i *InterleavingIter) yieldSyntheticSpanEndMarker() *base.InternalKV {
1018 1 : i.spanMarker.K.UserKey = i.endKey()
1019 1 : i.spanMarker.K.Trailer = base.MakeTrailer(base.InternalKeySeqNumMax, i.span.Keys[0].Kind())
1020 1 : return i.verify(&i.spanMarker)
1021 1 : }
1022 :
1023 1 : func (i *InterleavingIter) disablePrefixMode() {
1024 1 : if i.prefix != nil {
1025 1 : i.prefix = nil
1026 1 : // Clear the existing span. It may not hold the true end bound of the
1027 1 : // underlying span.
1028 1 : i.span = nil
1029 1 : }
1030 : }
1031 :
1032 1 : func (i *InterleavingIter) verify(kv *base.InternalKV) *base.InternalKV {
1033 1 : // Wrap the entire function body in the invariants build tag, so that
1034 1 : // production builds elide this entire function.
1035 1 : if invariants.Enabled {
1036 1 : switch {
1037 0 : case i.dir == -1 && i.spanMarkerTruncated:
1038 0 : panic("pebble: invariant violation: truncated span key in reverse iteration")
1039 : case kv != nil && i.opts.LowerBound != nil && !kv.K.IsExclusiveSentinel() &&
1040 0 : i.cmp(kv.K.UserKey, i.opts.LowerBound) < 0:
1041 0 : panic("pebble: invariant violation: key < lower bound")
1042 : case kv != nil && i.opts.UpperBound != nil && !kv.K.IsExclusiveSentinel() &&
1043 0 : !base.UserKeyExclusive(i.opts.UpperBound).IsUpperBoundForInternalKey(i.comparer.Compare, kv.K):
1044 0 : panic("pebble: invariant violation: key ≥ upper bound")
1045 0 : case i.err != nil && kv != nil:
1046 0 : panic("pebble: invariant violation: accumulated error swallowed")
1047 0 : case i.err == nil && i.pointIter.Error() != nil:
1048 0 : panic("pebble: invariant violation: pointIter swallowed")
1049 : }
1050 : }
1051 1 : return kv
1052 : }
1053 :
1054 1 : func (i *InterleavingIter) savedKeyspan() {
1055 1 : i.spanMarkerTruncated = false
1056 1 : i.maskSpanChangedCalled = false
1057 1 : }
1058 :
1059 : // updateMask updates the current mask, if a mask is configured and the mask
1060 : // hasn't been updated with the current keyspan yet.
1061 1 : func (i *InterleavingIter) maybeUpdateMask() {
1062 1 : switch {
1063 1 : case i.opts.Mask == nil, i.maskSpanChangedCalled:
1064 1 : return
1065 1 : case !i.withinSpan || i.span.Empty():
1066 1 : i.clearMask()
1067 1 : case i.truncated:
1068 1 : i.opts.Mask.SpanChanged(&i.truncatedSpan)
1069 1 : i.maskSpanChangedCalled = true
1070 1 : default:
1071 1 : i.opts.Mask.SpanChanged(i.span)
1072 1 : i.maskSpanChangedCalled = true
1073 : }
1074 : }
1075 :
1076 : // clearMask clears the current mask, if a mask is configured and no mask should
1077 : // be active.
1078 1 : func (i *InterleavingIter) clearMask() {
1079 1 : if i.opts.Mask != nil {
1080 1 : i.maskSpanChangedCalled = false
1081 1 : i.opts.Mask.SpanChanged(nil)
1082 1 : }
1083 : }
1084 :
1085 1 : func (i *InterleavingIter) startKey() []byte {
1086 1 : if i.truncated {
1087 1 : return i.truncatedSpan.Start
1088 1 : }
1089 1 : return i.span.Start
1090 : }
1091 :
1092 1 : func (i *InterleavingIter) endKey() []byte {
1093 1 : if i.truncated {
1094 1 : return i.truncatedSpan.End
1095 1 : }
1096 1 : return i.span.End
1097 : }
1098 :
1099 1 : func (i *InterleavingIter) savePoint(kv *base.InternalKV) {
1100 1 : i.pointKV = kv
1101 1 : if kv == nil {
1102 1 : i.err = firstError(i.err, i.pointIter.Error())
1103 1 : }
1104 1 : if invariants.Enabled {
1105 1 : if err := i.pointIter.Error(); kv != nil && err != nil {
1106 0 : panic(errors.WithSecondaryError(
1107 0 : base.AssertionFailedf("pebble: %T point iterator returned non-nil key %q while iter has error", i.pointIter, kv),
1108 0 : err))
1109 : }
1110 : }
1111 : }
1112 :
1113 : // Span returns the span covering the last key returned, if any. A span key is
1114 : // considered to 'cover' a key if the key falls within the span's user key
1115 : // bounds. The returned span is owned by the InterleavingIter. The caller is
1116 : // responsible for copying if stability is required.
1117 : //
1118 : // Span will never return an invalid or empty span.
1119 1 : func (i *InterleavingIter) Span() *Span {
1120 1 : if !i.withinSpan || len(i.span.Keys) == 0 {
1121 1 : return nil
1122 1 : } else if i.truncated {
1123 1 : return &i.truncatedSpan
1124 1 : }
1125 1 : return i.span
1126 : }
1127 :
1128 : // SetBounds implements (base.InternalIterator).SetBounds.
1129 1 : func (i *InterleavingIter) SetBounds(lower, upper []byte) {
1130 1 : i.opts.LowerBound, i.opts.UpperBound = lower, upper
1131 1 : i.pointIter.SetBounds(lower, upper)
1132 1 : i.Invalidate()
1133 1 : }
1134 :
1135 : // SetContext implements (base.InternalIterator).SetContext.
1136 0 : func (i *InterleavingIter) SetContext(ctx context.Context) {
1137 0 : i.pointIter.SetContext(ctx)
1138 0 : }
1139 :
1140 : // Invalidate invalidates the interleaving iterator's current position, clearing
1141 : // its state. This prevents optimizations such as reusing the current span on
1142 : // seek.
1143 1 : func (i *InterleavingIter) Invalidate() {
1144 1 : i.span = nil
1145 1 : i.pointKV = nil
1146 1 : }
1147 :
1148 : // Error implements (base.InternalIterator).Error.
1149 1 : func (i *InterleavingIter) Error() error {
1150 1 : return i.err
1151 1 : }
1152 :
1153 : // Close implements (base.InternalIterator).Close.
1154 1 : func (i *InterleavingIter) Close() error {
1155 1 : err := i.pointIter.Close()
1156 1 : i.keyspanIter.Close()
1157 1 : return err
1158 1 : }
1159 :
1160 : // String implements (base.InternalIterator).String.
1161 0 : func (i *InterleavingIter) String() string {
1162 0 : return fmt.Sprintf("keyspan-interleaving(%q)", i.pointIter.String())
1163 0 : }
1164 :
1165 1 : func firstError(err0, err1 error) error {
1166 1 : if err0 != nil {
1167 0 : return err0
1168 0 : }
1169 1 : return err1
1170 : }
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