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Add read/modify/write functionality to Put() api

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Summary: The application can set a callback function, which is applied on the previous value. And calculates the new value. This new value can be set, either inplace, if the previous value existed in memtable, and new value is smaller than previous value. Otherwise the new value is added normally.

Test Plan: fbmake. Added unit tests. All unit tests pass.

Reviewers: dhruba, haobo

Reviewed By: haobo

CC: sdong, kailiu, xinyaohu, sumeet, leveldb

Differential Revision: https://reviews.facebook.net/D14745
This commit is contained in:
Naman Gupta
2014-01-14 07:55:16 -08:00
parent aa0ef6602d
commit 8454cfe569
6 changed files with 309 additions and 70 deletions
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38
db/write_batch.cc
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@@ -115,7 +115,7 @@ Status WriteBatch::Iterate(Handler* handler) const {
return Status::Corruption("unknown WriteBatch tag");
}
}
if (found != WriteBatchInternal::Count(this)) {
if (found != WriteBatchInternal::Count(this)) {
return Status::Corruption("WriteBatch has wrong count");
} else {
return Status::OK();
@@ -194,14 +194,44 @@ class MemTableInserter : public WriteBatch::Handler {
}
virtual void Put(const Slice& key, const Slice& value) {
if (options_->inplace_update_support
&& mem_->Update(sequence_, kTypeValue, key, value)) {
if (!options_->inplace_update_support) {
mem_->Add(sequence_, kTypeValue, key, value);
} else if (options_->inplace_callback == nullptr) {
mem_->Update(sequence_, key, value);
RecordTick(options_->statistics.get(), NUMBER_KEYS_UPDATED);
} else {
mem_->Add(sequence_, kTypeValue, key, value);
if (mem_->UpdateCallback(sequence_, key, value, *options_)) {
RecordTick(options_->statistics.get(), NUMBER_KEYS_UPDATED);
} else {
// key not found in memtable. Do sst get/update/add
SnapshotImpl read_from_snapshot;
read_from_snapshot.number_ = sequence_;
ReadOptions ropts;
ropts.snapshot = &read_from_snapshot;
std::string prev_value;
std::string merged_value;
Status s = db_->Get(ropts, key, &prev_value);
char* prev_buffer = const_cast<char*>(prev_value.c_str());
size_t prev_size = prev_value.size();
if (options_->inplace_callback(s.ok() ? prev_buffer: nullptr,
s.ok() ? prev_size: 0,
value, &merged_value)) {
// prev_value is updated in-place with final value.
mem_->Add(sequence_, kTypeValue, key, Slice(prev_buffer, prev_size));
RecordTick(options_->statistics.get(), NUMBER_KEYS_WRITTEN);
} else {
// merged_value contains the final value. Only add if not empty.
if (!merged_value.empty()) {
mem_->Add(sequence_, kTypeValue, key, Slice(merged_value));
RecordTick(options_->statistics.get(), NUMBER_KEYS_WRITTEN);
}
}
}
}
sequence_++;
}
virtual void Merge(const Slice& key, const Slice& value) {
mem_->Add(sequence_, kTypeMerge, key, value);
sequence_++;