Line data Source code
1 : // Copyright 2018 The LevelDB-Go and Pebble Authors. All rights reserved. Use
2 : // of this source code is governed by a BSD-style license that can be found in
3 : // the LICENSE file.
4 :
5 : package pebble
6 :
7 : import (
8 : "context"
9 : "fmt"
10 :
11 : "github.com/cockroachdb/pebble/internal/base"
12 : "github.com/cockroachdb/pebble/internal/keyspan"
13 : "github.com/cockroachdb/pebble/internal/manifest"
14 : "github.com/cockroachdb/pebble/sstable"
15 : )
16 :
17 : // getIter is an internal iterator used to perform gets. It iterates through
18 : // the values for a particular key, level by level. It is not a general purpose
19 : // internalIterator, but specialized for Get operations so that it loads data
20 : // lazily.
21 : type getIter struct {
22 : logger Logger
23 : comparer *Comparer
24 : newIters tableNewIters
25 : snapshot uint64
26 : key []byte
27 : iter internalIterator
28 : rangeDelIter keyspan.FragmentIterator
29 : tombstone *keyspan.Span
30 : levelIter levelIter
31 : level int
32 : batch *Batch
33 : mem flushableList
34 : l0 []manifest.LevelSlice
35 : version *version
36 : iterKey *InternalKey
37 : iterValue base.LazyValue
38 : err error
39 : }
40 :
41 : // TODO(sumeer): CockroachDB code doesn't use getIter, but, for completeness,
42 : // make this implement InternalIteratorWithStats.
43 :
44 : // getIter implements the base.InternalIterator interface.
45 : var _ base.InternalIterator = (*getIter)(nil)
46 :
47 0 : func (g *getIter) String() string {
48 0 : return fmt.Sprintf("len(l0)=%d, len(mem)=%d, level=%d", len(g.l0), len(g.mem), g.level)
49 0 : }
50 :
51 0 : func (g *getIter) SeekGE(key []byte, flags base.SeekGEFlags) (*InternalKey, base.LazyValue) {
52 0 : panic("pebble: SeekGE unimplemented")
53 : }
54 :
55 : func (g *getIter) SeekPrefixGE(
56 : prefix, key []byte, flags base.SeekGEFlags,
57 0 : ) (*base.InternalKey, base.LazyValue) {
58 0 : panic("pebble: SeekPrefixGE unimplemented")
59 : }
60 :
61 0 : func (g *getIter) SeekLT(key []byte, flags base.SeekLTFlags) (*InternalKey, base.LazyValue) {
62 0 : panic("pebble: SeekLT unimplemented")
63 : }
64 :
65 2 : func (g *getIter) First() (*InternalKey, base.LazyValue) {
66 2 : return g.Next()
67 2 : }
68 :
69 0 : func (g *getIter) Last() (*InternalKey, base.LazyValue) {
70 0 : panic("pebble: Last unimplemented")
71 : }
72 :
73 2 : func (g *getIter) Next() (*InternalKey, base.LazyValue) {
74 2 : if g.iter != nil {
75 2 : g.iterKey, g.iterValue = g.iter.Next()
76 2 : }
77 :
78 2 : for {
79 2 : if g.iter != nil {
80 2 : // We have to check rangeDelIter on each iteration because a single
81 2 : // user-key can be spread across multiple tables in a level. A range
82 2 : // tombstone will appear in the table corresponding to its start
83 2 : // key. Every call to levelIter.Next() potentially switches to a new
84 2 : // table and thus reinitializes rangeDelIter.
85 2 : if g.rangeDelIter != nil {
86 2 : g.tombstone = keyspan.Get(g.comparer.Compare, g.rangeDelIter, g.key)
87 2 : if g.err = g.rangeDelIter.Close(); g.err != nil {
88 0 : return nil, base.LazyValue{}
89 0 : }
90 2 : g.rangeDelIter = nil
91 : }
92 :
93 2 : if g.iterKey != nil {
94 2 : key := g.iterKey
95 2 : if g.tombstone != nil && g.tombstone.CoversAt(g.snapshot, key.SeqNum()) {
96 2 : // We have a range tombstone covering this key. Rather than return a
97 2 : // point or range deletion here, we return false and close our
98 2 : // internal iterator which will make Valid() return false,
99 2 : // effectively stopping iteration.
100 2 : g.err = g.iter.Close()
101 2 : g.iter = nil
102 2 : return nil, base.LazyValue{}
103 2 : }
104 2 : if g.comparer.Equal(g.key, key.UserKey) {
105 2 : if !key.Visible(g.snapshot, base.InternalKeySeqNumMax) {
106 2 : g.iterKey, g.iterValue = g.iter.Next()
107 2 : continue
108 : }
109 2 : return g.iterKey, g.iterValue
110 : }
111 : }
112 : // We've advanced the iterator passed the desired key. Move on to the
113 : // next memtable / level.
114 2 : g.err = g.iter.Close()
115 2 : g.iter = nil
116 2 : if g.err != nil {
117 1 : return nil, base.LazyValue{}
118 1 : }
119 : }
120 :
121 : // Create an iterator from the batch.
122 2 : if g.batch != nil {
123 2 : if g.batch.index == nil {
124 0 : g.err = ErrNotIndexed
125 0 : g.iterKey, g.iterValue = nil, base.LazyValue{}
126 0 : return nil, base.LazyValue{}
127 0 : }
128 2 : g.iter = g.batch.newInternalIter(nil)
129 2 : g.rangeDelIter = g.batch.newRangeDelIter(
130 2 : nil,
131 2 : // Get always reads the entirety of the batch's history, so no
132 2 : // batch keys should be filtered.
133 2 : base.InternalKeySeqNumMax,
134 2 : )
135 2 : g.iterKey, g.iterValue = g.iter.SeekGE(g.key, base.SeekGEFlagsNone)
136 2 : g.batch = nil
137 2 : continue
138 : }
139 :
140 : // If we have a tombstone from a previous level it is guaranteed to delete
141 : // keys in lower levels.
142 2 : if g.tombstone != nil && g.tombstone.VisibleAt(g.snapshot) {
143 2 : return nil, base.LazyValue{}
144 2 : }
145 :
146 : // Create iterators from memtables from newest to oldest.
147 2 : if n := len(g.mem); n > 0 {
148 2 : m := g.mem[n-1]
149 2 : g.iter = m.newIter(nil)
150 2 : g.rangeDelIter = m.newRangeDelIter(nil)
151 2 : g.mem = g.mem[:n-1]
152 2 : g.iterKey, g.iterValue = g.iter.SeekGE(g.key, base.SeekGEFlagsNone)
153 2 : continue
154 : }
155 :
156 2 : if g.level == 0 {
157 2 : // Create iterators from L0 from newest to oldest.
158 2 : if n := len(g.l0); n > 0 {
159 2 : files := g.l0[n-1].Iter()
160 2 : g.l0 = g.l0[:n-1]
161 2 : iterOpts := IterOptions{
162 2 : // TODO(sumeer): replace with a parameter provided by the caller.
163 2 : CategoryAndQoS: sstable.CategoryAndQoS{
164 2 : Category: "pebble-get",
165 2 : QoSLevel: sstable.LatencySensitiveQoSLevel,
166 2 : },
167 2 : logger: g.logger,
168 2 : snapshotForHideObsoletePoints: g.snapshot}
169 2 : g.levelIter.init(context.Background(), iterOpts, g.comparer, g.newIters,
170 2 : files, manifest.L0Sublevel(n), internalIterOpts{})
171 2 : g.levelIter.initRangeDel(&g.rangeDelIter)
172 2 : bc := levelIterBoundaryContext{}
173 2 : g.levelIter.initBoundaryContext(&bc)
174 2 : g.iter = &g.levelIter
175 2 :
176 2 : // Compute the key prefix for bloom filtering if split function is
177 2 : // specified, or use the user key as default.
178 2 : prefix := g.key
179 2 : if g.comparer.Split != nil {
180 2 : prefix = g.key[:g.comparer.Split(g.key)]
181 2 : }
182 2 : g.iterKey, g.iterValue = g.iter.SeekPrefixGE(prefix, g.key, base.SeekGEFlagsNone)
183 2 : if bc.isSyntheticIterBoundsKey || bc.isIgnorableBoundaryKey {
184 2 : g.iterKey = nil
185 2 : g.iterValue = base.LazyValue{}
186 2 : }
187 2 : continue
188 : }
189 2 : g.level++
190 : }
191 :
192 2 : if g.level >= numLevels {
193 2 : return nil, base.LazyValue{}
194 2 : }
195 2 : if g.version.Levels[g.level].Empty() {
196 2 : g.level++
197 2 : continue
198 : }
199 :
200 2 : iterOpts := IterOptions{
201 2 : // TODO(sumeer): replace with a parameter provided by the caller.
202 2 : CategoryAndQoS: sstable.CategoryAndQoS{
203 2 : Category: "pebble-get",
204 2 : QoSLevel: sstable.LatencySensitiveQoSLevel,
205 2 : }, logger: g.logger, snapshotForHideObsoletePoints: g.snapshot}
206 2 : g.levelIter.init(context.Background(), iterOpts, g.comparer, g.newIters,
207 2 : g.version.Levels[g.level].Iter(), manifest.Level(g.level), internalIterOpts{})
208 2 : g.levelIter.initRangeDel(&g.rangeDelIter)
209 2 : bc := levelIterBoundaryContext{}
210 2 : g.levelIter.initBoundaryContext(&bc)
211 2 : g.level++
212 2 : g.iter = &g.levelIter
213 2 :
214 2 : // Compute the key prefix for bloom filtering if split function is
215 2 : // specified, or use the user key as default.
216 2 : prefix := g.key
217 2 : if g.comparer.Split != nil {
218 2 : prefix = g.key[:g.comparer.Split(g.key)]
219 2 : }
220 2 : g.iterKey, g.iterValue = g.iter.SeekPrefixGE(prefix, g.key, base.SeekGEFlagsNone)
221 2 : if bc.isSyntheticIterBoundsKey || bc.isIgnorableBoundaryKey {
222 2 : g.iterKey = nil
223 2 : g.iterValue = base.LazyValue{}
224 2 : }
225 : }
226 : }
227 :
228 0 : func (g *getIter) Prev() (*InternalKey, base.LazyValue) {
229 0 : panic("pebble: Prev unimplemented")
230 : }
231 :
232 0 : func (g *getIter) NextPrefix([]byte) (*InternalKey, base.LazyValue) {
233 0 : panic("pebble: NextPrefix unimplemented")
234 : }
235 :
236 0 : func (g *getIter) Valid() bool {
237 0 : return g.iterKey != nil && g.err == nil
238 0 : }
239 :
240 1 : func (g *getIter) Error() error {
241 1 : return g.err
242 1 : }
243 :
244 2 : func (g *getIter) Close() error {
245 2 : if g.iter != nil {
246 2 : if err := g.iter.Close(); err != nil && g.err == nil {
247 0 : g.err = err
248 0 : }
249 2 : g.iter = nil
250 : }
251 2 : return g.err
252 : }
253 :
254 0 : func (g *getIter) SetBounds(lower, upper []byte) {
255 0 : panic("pebble: SetBounds unimplemented")
256 : }
257 :
258 0 : func (g *getIter) SetContext(_ context.Context) {}
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