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rocksdb/HISTORY.md
Igor Canadi 0b4ccf765c Flushes should always go to HIGH priority thread pool 
Summary:
This is not column-family related diff. It is in columnfamily branch because the change is significant and we want to push it with next major release (3.0).

It removes the leveldb notion of one thread pool and expands it to two thread pools by default (HIGH and LOW). Flush process is removed from compaction process and all flush threads are executed on HIGH thread pool, since we don't want long-running compactions to influence flush latency.

Test Plan: make check

Reviewers: dhruba, haobo, kailiu, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15987
2014-02-06 14:17:13 -08:00

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Rocksdb Change Log

Unreleased (will be released in 3.0)

  • By default, max_background_flushes is 1 and flush process is removed from background compaction process. Flush process is now always executed in high priority thread pool.

Unreleased (will be relased in 2.8)

  • By default, checksums are verified on every read from database

2.7.0 (01/28/2014)

Public API changes

  • Renamed StackableDB::GetRawDB() to StackableDB::GetBaseDB().
  • Renamed WriteBatch::Data() const std::string& Data() const.
  • Renamed class TableStats to TableProperties.
  • Deleted class PrefixHashRepFactory. Please use NewHashSkipListRepFactory() instead.
  • Supported multi-threaded EnableFileDeletions() and DisableFileDeletions().
  • Added DB::GetOptions().
  • Added DB::GetDbIdentity().

New Features

  • Added BackupableDB
  • Implemented TailingIterator, a special type of iterator that doesn't create a snapshot (can be used to read newly inserted data) and is optimized for doing sequential reads.
  • Added property block for table, which allows (1) a table to store its metadata and (2) end user to collect and store properties they are interested in.
  • Enabled caching index and filter block in block cache (turned off by default).
  • Supported error report when doing manual compaction.
  • Supported additional Linux platform flavors and Mac OS.
  • Put with SliceParts - Variant of Put() that gathers output like writev(2)
  • Bug fixes and code refactor for compatibility with upcoming Column Family feature.

Performance Improvements

  • Huge benchmark performance improvements by multiple efforts. For example, increase in readonly QPS from about 530k in 2.6 release to 1.1 million in 2.7 [1]
  • Speeding up a way RocksDB deleted obsolete files - no longer listing the whole directory under a lock -- decrease in p99
  • Use raw pointer instead of shared pointer for statistics: 5b825d -- huge increase in performance -- shared pointers are slow
  • Optimized locking for Get() -- 1fdb3f -- 1.5x QPS increase for some workloads
  • Cache speedup - e8d40c3
  • Implemented autovector, which allocates first N elements on stack. Most of vectors in RocksDB are small. Also, we never want to allocate heap objects while holding a mutex. -- c01676e4
  • Lots of efforts to move malloc, memcpy and IO outside of locks