RocksDB 5.8

5.8 (09/28/2017)

Public API Change

• Users of Statistics::getHistogramString() will see fewer histogram buckets and different bucket endpoints.
• Slice::compare and BytewiseComparator Compare no longer accept Slices containing nullptr.
• Transaction::Get and Transaction::GetForUpdate variants with PinnableSlice added.

New Features

• Add Iterator::Refresh(), which allows users to update the iterator state so that they can avoid some initialization costs of recreating iterators.
• Replace dynamic_cast<> (except unit test) so people can choose to build with RTTI off. With make, release mode is by default built with -fno-rtti and debug mode is built without it. Users can override it by setting USE_RTTI=0 or 1.
• Universal compactions including the bottom level can be executed in a dedicated thread pool. This alleviates head-of-line blocking in the compaction queue, which cause write stalling, particularly in multi-instance use cases. Users can enable this feature via Env::SetBackgroundThreads(N, Env::Priority::BOTTOM), where N > 0.
• Allow merge operator to be called even with a single merge operand during compactions, by appropriately overriding MergeOperator::AllowSingleOperand.
• Add DB::VerifyChecksum(), which verifies the checksums in all SST files in a running DB.
  Block-based table support for disabling checksums by setting BlockBasedTableOptions::checksum = kNoChecksum.

Bug Fixes

• Fix wrong latencies in rocksdb.db.get.micros, rocksdb.db.write.micros, and rocksdb.sst.read.micros.
• Fix incorrect dropping of deletions during intra-L0 compaction.
• Fix transient reappearance of keys covered by range deletions when memtable prefix bloom filter is enabled.
• Fix potentially wrong file smallest key when range deletions separated by snapshot are written together.