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Use same sorting for all level 0 files

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Summary:
We decided that one of the long term goals is to unify level and universal compaction.

As a small first step, I'm unifying level 0 sorting methods.

Previously, we used to sort level 0 files in level compaction by file number and in universal compaction by sequence number.

But it turns out that in level compaction, sorting by file number is exactly the same as sorting by sequence number.

Test Plan:
Ran make check with bunch of asserts to verify the sorting order is exactly the same.
Also, make check with this patch

Reviewers: haobo, yhchiang, ljin, dhruba, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19131
This commit is contained in:
Igor Canadi 2014-06-20 09:12:14 +02:00
parent 7a9dd5f214
commit 107e08baa7
1 changed files with 8 additions and 24 deletions
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32
db/version_set.cc
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@ -445,9 +445,6 @@ static bool SaveValue(void* arg, const ParsedInternalKey& parsed_key,
}
namespace {
bool NewestFirst(FileMetaData* a, FileMetaData* b) {
return a->fd.GetNumber() > b->fd.GetNumber();
}
bool NewestFirstBySeqNo(FileMetaData* a, FileMetaData* b) {
if (a->smallest_seqno != b->smallest_seqno) {
return a->smallest_seqno > b->smallest_seqno;
@ -456,7 +453,7 @@ bool NewestFirstBySeqNo(FileMetaData* a, FileMetaData* b) {
return a->largest_seqno > b->largest_seqno;
}
// Break ties by file number
return NewestFirst(a, b);
return a->fd.GetNumber() > b->fd.GetNumber();
}
bool BySmallestKey(FileMetaData* a, FileMetaData* b,
const InternalKeyComparator* cmp) {
@ -655,11 +652,7 @@ void Version::Get(const ReadOptions& options,
assert(comp_sign < 0);
} else {
// level == 0, the current file cannot be newer than the previous one.
if (cfd_->options()->compaction_style == kCompactionStyleUniversal) {
assert(!NewestFirstBySeqNo(f, prev_file));
} else {
assert(!NewestFirst(f, prev_file));
}
assert(!NewestFirstBySeqNo(f, prev_file));
}
}
prev_file = f;
@ -1318,22 +1311,18 @@ struct VersionSet::ManifestWriter {
class VersionSet::Builder {
private:
// Helper to sort v->files_
// kLevel0LevelCompaction -- NewestFirst (also used for FIFO compaction)
// kLevel0UniversalCompaction -- NewestFirstBySeqNo
// kLevel0 -- NewestFirstBySeqNo
// kLevelNon0 -- BySmallestKey
struct FileComparator {
enum SortMethod {
kLevel0LevelCompaction = 0,
kLevel0UniversalCompaction = 1,
kLevelNon0 = 2,
kLevel0 = 0,
kLevelNon0 = 1,
} sort_method;
const InternalKeyComparator* internal_comparator;
bool operator()(FileMetaData* f1, FileMetaData* f2) const {
switch (sort_method) {
case kLevel0LevelCompaction:
return NewestFirst(f1, f2);
case kLevel0UniversalCompaction:
case kLevel0:
return NewestFirstBySeqNo(f1, f2);
case kLevelNon0:
return BySmallestKey(f1, f2, internal_comparator);
@ -1359,10 +1348,7 @@ class VersionSet::Builder {
Builder(ColumnFamilyData* cfd) : cfd_(cfd), base_(cfd->current()) {
base_->Ref();
levels_ = new LevelState[base_->NumberLevels()];
level_zero_cmp_.sort_method =
(cfd_->options()->compaction_style == kCompactionStyleUniversal)
? FileComparator::kLevel0UniversalCompaction
: FileComparator::kLevel0LevelCompaction;
level_zero_cmp_.sort_method = FileComparator::kLevel0;
level_nonzero_cmp_.sort_method = FileComparator::kLevelNon0;
level_nonzero_cmp_.internal_comparator = &cfd->internal_comparator();
@ -1408,9 +1394,7 @@ class VersionSet::Builder {
auto f2 = v->files_[level][i];
if (level == 0) {
assert(level_zero_cmp_(f1, f2));
if (cfd_->options()->compaction_style == kCompactionStyleUniversal) {
assert(f1->largest_seqno > f2->largest_seqno);
}
assert(f1->largest_seqno > f2->largest_seqno);
} else {
assert(level_nonzero_cmp_(f1, f2));