Line data Source code
1 : // Copyright 2022 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 :
10 : "github.com/cockroachdb/errors"
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 : "github.com/cockroachdb/pebble/sstable/block"
16 : )
17 :
18 : // NewExternalIter takes an input 2d array of sstable files which may overlap
19 : // across subarrays but not within a subarray (at least as far as points are
20 : // concerned; range keys are allowed to overlap arbitrarily even within a
21 : // subarray), and returns an Iterator over the merged contents of the sstables.
22 : // Input sstables may contain point keys, range keys, range deletions, etc. The
23 : // input files slice must be sorted in reverse chronological ordering. A key in a
24 : // file at a lower index subarray will shadow a key with an identical user key
25 : // contained within a file at a higher index subarray. Each subarray must be
26 : // sorted in internal key order, where lower index files contain keys that sort
27 : // left of files with higher indexes.
28 : //
29 : // Input sstables must only contain keys with the zero sequence number.
30 : //
31 : // Iterators constructed through NewExternalIter do not support all iterator
32 : // options, including block-property and table filters. NewExternalIter errors
33 : // if an incompatible option is set.
34 : func NewExternalIter(
35 : o *Options, iterOpts *IterOptions, files [][]sstable.ReadableFile,
36 1 : ) (it *Iterator, err error) {
37 1 : return NewExternalIterWithContext(context.Background(), o, iterOpts, files)
38 1 : }
39 :
40 : // NewExternalIterWithContext is like NewExternalIter, and additionally
41 : // accepts a context for tracing.
42 : func NewExternalIterWithContext(
43 : ctx context.Context, o *Options, iterOpts *IterOptions, files [][]sstable.ReadableFile,
44 1 : ) (it *Iterator, err error) {
45 1 : if iterOpts != nil {
46 1 : if err := validateExternalIterOpts(iterOpts); err != nil {
47 0 : return nil, err
48 0 : }
49 : }
50 :
51 1 : var readers [][]*sstable.Reader
52 1 :
53 1 : seqNumOffset := 0
54 1 : for _, levelFiles := range files {
55 1 : seqNumOffset += len(levelFiles)
56 1 : }
57 1 : for _, levelFiles := range files {
58 1 : seqNumOffset -= len(levelFiles)
59 1 : subReaders, err := openExternalTables(ctx, o, levelFiles, seqNumOffset, o.MakeReaderOptions())
60 1 : readers = append(readers, subReaders)
61 1 : if err != nil {
62 0 : // Close all the opened readers.
63 0 : for i := range readers {
64 0 : for j := range readers[i] {
65 0 : _ = readers[i][j].Close()
66 0 : }
67 : }
68 0 : return nil, err
69 : }
70 : }
71 :
72 1 : buf := iterAllocPool.Get().(*iterAlloc)
73 1 : dbi := &buf.dbi
74 1 : *dbi = Iterator{
75 1 : ctx: ctx,
76 1 : alloc: buf,
77 1 : merge: o.Merger.Merge,
78 1 : comparer: *o.Comparer,
79 1 : readState: nil,
80 1 : keyBuf: buf.keyBuf,
81 1 : prefixOrFullSeekKey: buf.prefixOrFullSeekKey,
82 1 : boundsBuf: buf.boundsBuf,
83 1 : batch: nil,
84 1 : // Add the readers to the Iterator so that Close closes them, and
85 1 : // SetOptions can re-construct iterators from them.
86 1 : externalReaders: readers,
87 1 : newIters: func(context.Context, *manifest.FileMetadata, *IterOptions,
88 1 : internalIterOpts, iterKinds) (iterSet, error) {
89 0 : // NB: External iterators are currently constructed without any
90 0 : // `levelIters`. newIters should never be called. When we support
91 0 : // organizing multiple non-overlapping files into a single level
92 0 : // (see TODO below), we'll need to adjust this tableNewIters
93 0 : // implementation to open iterators by looking up f in a map
94 0 : // of readers indexed by *fileMetadata.
95 0 : panic("unreachable")
96 : },
97 : seqNum: base.SeqNumMax,
98 : }
99 1 : if iterOpts != nil {
100 1 : dbi.opts = *iterOpts
101 1 : dbi.processBounds(iterOpts.LowerBound, iterOpts.UpperBound)
102 1 : }
103 1 : if err := finishInitializingExternal(ctx, dbi); err != nil {
104 0 : dbi.Close()
105 0 : return nil, err
106 0 : }
107 1 : return dbi, nil
108 : }
109 :
110 1 : func validateExternalIterOpts(iterOpts *IterOptions) error {
111 1 : switch {
112 0 : case iterOpts.PointKeyFilters != nil:
113 0 : return errors.Errorf("pebble: external iterator: PointKeyFilters unsupported")
114 0 : case iterOpts.RangeKeyFilters != nil:
115 0 : return errors.Errorf("pebble: external iterator: RangeKeyFilters unsupported")
116 0 : case iterOpts.OnlyReadGuaranteedDurable:
117 0 : return errors.Errorf("pebble: external iterator: OnlyReadGuaranteedDurable unsupported")
118 0 : case iterOpts.UseL6Filters:
119 0 : return errors.Errorf("pebble: external iterator: UseL6Filters unsupported")
120 : }
121 1 : return nil
122 : }
123 :
124 1 : func createExternalPointIter(ctx context.Context, it *Iterator) (topLevelIterator, error) {
125 1 : // TODO(jackson): In some instances we could generate fewer levels by using
126 1 : // L0Sublevels code to organize nonoverlapping files into the same level.
127 1 : // This would allow us to use levelIters and keep a smaller set of data and
128 1 : // files in-memory. However, it would also require us to identify the bounds
129 1 : // of all the files upfront.
130 1 :
131 1 : if !it.opts.pointKeys() {
132 0 : return emptyIter, nil
133 1 : } else if it.pointIter != nil {
134 1 : return it.pointIter, nil
135 1 : }
136 1 : mlevels := it.alloc.mlevels[:0]
137 1 :
138 1 : // TODO(jackson): External iterators never provide categorized iterator
139 1 : // stats today because they exist outside the context of a *DB. If the
140 1 : // sstables being read are on the physical filesystem, we may still want to
141 1 : // thread a CategoryStatsCollector through so that we collect their stats.
142 1 :
143 1 : if len(it.externalReaders) > cap(mlevels) {
144 0 : mlevels = make([]mergingIterLevel, 0, len(it.externalReaders))
145 0 : }
146 : // We set a synthetic sequence number, with lower levels having higer numbers.
147 1 : seqNum := 0
148 1 : for _, readers := range it.externalReaders {
149 1 : seqNum += len(readers)
150 1 : }
151 1 : for _, readers := range it.externalReaders {
152 1 : for _, r := range readers {
153 1 : var (
154 1 : rangeDelIter keyspan.FragmentIterator
155 1 : pointIter internalIterator
156 1 : err error
157 1 : )
158 1 : // We could set hideObsoletePoints=true, since we are reading at
159 1 : // InternalKeySeqNumMax, but we don't bother since these sstables should
160 1 : // not have obsolete points (so the performance optimization is
161 1 : // unnecessary), and we don't want to bother constructing a
162 1 : // BlockPropertiesFilterer that includes obsoleteKeyBlockPropertyFilter.
163 1 : transforms := sstable.IterTransforms{SyntheticSeqNum: sstable.SyntheticSeqNum(seqNum)}
164 1 : seqNum--
165 1 : pointIter, err = r.NewPointIter(
166 1 : ctx, transforms, it.opts.LowerBound, it.opts.UpperBound, nil, /* BlockPropertiesFilterer */
167 1 : sstable.NeverUseFilterBlock,
168 1 : block.ReadEnv{Stats: &it.stats.InternalStats, IterStats: nil},
169 1 : sstable.MakeTrivialReaderProvider(r))
170 1 : if err != nil {
171 0 : return nil, err
172 0 : }
173 1 : rangeDelIter, err = r.NewRawRangeDelIter(ctx, sstable.FragmentIterTransforms{
174 1 : SyntheticSeqNum: sstable.SyntheticSeqNum(seqNum),
175 1 : }, block.ReadEnv{Stats: &it.stats.InternalStats, IterStats: nil})
176 1 : if err != nil {
177 0 : return nil, err
178 0 : }
179 1 : mlevels = append(mlevels, mergingIterLevel{
180 1 : iter: pointIter,
181 1 : rangeDelIter: rangeDelIter,
182 1 : })
183 : }
184 : }
185 :
186 1 : it.alloc.merging.init(&it.opts, &it.stats.InternalStats, it.comparer.Compare, it.comparer.Split, mlevels...)
187 1 : it.alloc.merging.snapshot = base.SeqNumMax
188 1 : if len(mlevels) <= cap(it.alloc.levelsPositioned) {
189 1 : it.alloc.merging.levelsPositioned = it.alloc.levelsPositioned[:len(mlevels)]
190 1 : }
191 1 : return &it.alloc.merging, nil
192 : }
193 :
194 1 : func finishInitializingExternal(ctx context.Context, it *Iterator) error {
195 1 : pointIter, err := createExternalPointIter(ctx, it)
196 1 : if err != nil {
197 0 : return err
198 0 : }
199 1 : it.pointIter = pointIter
200 1 : it.iter = it.pointIter
201 1 :
202 1 : if it.opts.rangeKeys() {
203 1 : it.rangeKeyMasking.init(it, &it.comparer)
204 1 : var rangeKeyIters []keyspan.FragmentIterator
205 1 : if it.rangeKey == nil {
206 1 : // We could take advantage of the lack of overlaps in range keys within
207 1 : // each slice in it.externalReaders, and generate keyspanimpl.LevelIters
208 1 : // out of those. However, since range keys are expected to be sparse to
209 1 : // begin with, the performance gain might not be significant enough to
210 1 : // warrant it.
211 1 : //
212 1 : // TODO(bilal): Explore adding a simpleRangeKeyLevelIter that does not
213 1 : // operate on FileMetadatas (similar to simpleLevelIter), and implements
214 1 : // this optimization.
215 1 : // We set a synthetic sequence number, with lower levels having higer numbers.
216 1 : seqNum := 0
217 1 : for _, readers := range it.externalReaders {
218 1 : seqNum += len(readers)
219 1 : }
220 1 : for _, readers := range it.externalReaders {
221 1 : for _, r := range readers {
222 1 : transforms := sstable.FragmentIterTransforms{SyntheticSeqNum: sstable.SyntheticSeqNum(seqNum)}
223 1 : seqNum--
224 1 : if rki, err := r.NewRawRangeKeyIter(ctx, transforms, block.ReadEnv{Stats: &it.stats.InternalStats, IterStats: nil}); err != nil {
225 0 : return err
226 1 : } else if rki != nil {
227 1 : rangeKeyIters = append(rangeKeyIters, rki)
228 1 : }
229 : }
230 : }
231 1 : if len(rangeKeyIters) > 0 {
232 1 : it.rangeKey = iterRangeKeyStateAllocPool.Get().(*iteratorRangeKeyState)
233 1 : it.rangeKey.init(it.comparer.Compare, it.comparer.Split, &it.opts)
234 1 : it.rangeKey.rangeKeyIter = it.rangeKey.iterConfig.Init(
235 1 : &it.comparer,
236 1 : base.SeqNumMax,
237 1 : it.opts.LowerBound, it.opts.UpperBound,
238 1 : &it.hasPrefix, &it.prefixOrFullSeekKey,
239 1 : false /* internalKeys */, &it.rangeKey.internal,
240 1 : )
241 1 : for i := range rangeKeyIters {
242 1 : it.rangeKey.iterConfig.AddLevel(rangeKeyIters[i])
243 1 : }
244 : }
245 : }
246 1 : if it.rangeKey != nil {
247 1 : it.rangeKey.iiter.Init(&it.comparer, it.iter, it.rangeKey.rangeKeyIter,
248 1 : keyspan.InterleavingIterOpts{
249 1 : Mask: &it.rangeKeyMasking,
250 1 : LowerBound: it.opts.LowerBound,
251 1 : UpperBound: it.opts.UpperBound,
252 1 : })
253 1 : it.iter = &it.rangeKey.iiter
254 1 : }
255 : }
256 1 : return nil
257 : }
258 :
259 : func openExternalTables(
260 : ctx context.Context,
261 : o *Options,
262 : files []sstable.ReadableFile,
263 : seqNumOffset int,
264 : readerOpts sstable.ReaderOptions,
265 1 : ) (readers []*sstable.Reader, err error) {
266 1 : readers = make([]*sstable.Reader, 0, len(files))
267 1 : for i := range files {
268 1 : readable, err := sstable.NewSimpleReadable(files[i])
269 1 : if err != nil {
270 0 : return readers, err
271 0 : }
272 1 : r, err := sstable.NewReader(ctx, readable, readerOpts)
273 1 : if err != nil {
274 0 : return readers, err
275 0 : }
276 1 : readers = append(readers, r)
277 : }
278 1 : return readers, err
279 : }
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