release 5.9

Summary:
updated HISTORY.md and version.h for the release.
Closes https://github.com/facebook/rocksdb/pull/3110

Differential Revision: D6218645

Pulled By: ajkr

fbshipit-source-id: 99ab8473e9088b02d7596e92351cce7a60a99e93

HISTORY.md

@@ -1,6 +1,11 @@
 # Rocksdb Change Log
 ## Unreleased
 ### Public API Change
+### New Features
+### Bug Fixes
+
+## 5.9.0 (11/1/2017)
+### Public API Change
 * `BackupableDBOptions::max_valid_backups_to_open == 0` now means no backups will be opened during BackupEngine initialization. Previously this condition disabled limiting backups opened.
 * `DBOptions::preserve_deletes` is a new option that allows one to specify that DB should not drop tombstones for regular deletes if they have sequence number larger than what was set by the new API call `DB::SetPreserveDeletesSequenceNumber(SequenceNumber seqnum)`. Disabled by default.
 * API call `DB::SetPreserveDeletesSequenceNumber(SequenceNumber seqnum)` was added, users who wish to preserve deletes are expected to periodically call this function to advance the cutoff seqnum (all deletes made before this seqnum can be dropped by DB). It's user responsibility to figure out how to advance the seqnum in the way so the tombstones are kept for the desired period of time, yet are eventually processed in time and don't eat up too much space.

include/rocksdb/version.h

@@ -5,7 +5,7 @@
 #pragma once
 
 #define ROCKSDB_MAJOR 5
-#define ROCKSDB_MINOR 8
+#define ROCKSDB_MINOR 9
 #define ROCKSDB_PATCH 0
 
 // Do not use these. We made the mistake of declaring macros starting with