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Merging iterator to disble reseek optimization in prefix seek (#5815)

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Summary:
We are seeing a bug of wrong results with merging iterator's reseek avoidence feature and prefix extractor. Disable this optimization for now.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5815

Test Plan: Validated the same MyRocks case was fixed; run all existing tests.

Differential Revision: D17430776

fbshipit-source-id: aef664277ba0ab8a2e68331ff0db6ae682535371
This commit is contained in:
sdong 2019-09-17 17:08:57 -07:00
parent d3f28558e7
commit 648b0141fa
2 changed files with 41 additions and 1 deletions
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40
db/db_test2.cc
View File

@ -3771,6 +3771,46 @@ TEST_F(DBTest2, CloseWithUnreleasedSnapshot) {
delete db_;
db_ = nullptr;
}
TEST_F(DBTest2, PrefixBloomReseek) {
Options options = CurrentOptions();
options.create_if_missing = true;
options.prefix_extractor.reset(NewCappedPrefixTransform(3));
BlockBasedTableOptions bbto;
bbto.filter_policy.reset(NewBloomFilterPolicy(10, false));
bbto.whole_key_filtering = false;
options.table_factory.reset(NewBlockBasedTableFactory(bbto));
DestroyAndReopen(options);
// Construct two L1 files with keys:
// f1:[aaa1 ccc1] f2:[ddd0]
ASSERT_OK(Put("aaa1", ""));
ASSERT_OK(Put("ccc1", ""));
ASSERT_OK(Flush());
ASSERT_OK(Put("ddd0", ""));
ASSERT_OK(Flush());
CompactRangeOptions cro;
cro.bottommost_level_compaction = BottommostLevelCompaction::kSkip;
ASSERT_OK(db_->CompactRange(cro, nullptr, nullptr));
ASSERT_OK(Put("bbb1", ""));
Iterator* iter = db_->NewIterator(ReadOptions());
// Seeking into f1, the iterator will check bloom filter which returns the
// file iterator ot be invalidate, and the cursor will put into f2, with
// the next key to be "ddd0".
iter->Seek("bbb1");
ASSERT_TRUE(iter->Valid());
ASSERT_EQ("bbb1", iter->key().ToString());
// Reseek ccc1, the L1 iterator needs to go back to f1 and reseek.
iter->Seek("ccc1");
ASSERT_TRUE(iter->Valid());
ASSERT_EQ("ccc1", iter->key().ToString());
delete iter;
}
} // namespace rocksdb
int main(int argc, char** argv) {

2
table/merging_iterator.cc
View File

@ -129,7 +129,7 @@ class MergingIterator : public InternalIterator {
void Seek(const Slice& target) override {
bool is_increasing_reseek = false;
if (current_ != nullptr && direction_ == kForward && status_.ok() &&
comparator_->Compare(target, key()) >= 0) {
!prefix_seek_mode_ && comparator_->Compare(target, key()) >= 0) {
is_increasing_reseek = true;
}
ClearHeaps();