Summary:
Currently, when something badly happen in the DB::Write() while the write-queue
contains more than one element, the current design seems to forget to clean up
the queue as well as wake-up all the writers, this potentially makes rocksdb
hang on writes.

Test Plan: make all check

Reviewers: sdong, ljin, igor, haobo

Reviewed By: haobo

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19167

Summary: asan_crash_test is failing on segfault

Test Plan: running asan_crash_test

Reviewers: sdong, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19149

Summary:
We added multiple fields to FileMetaData recently and are planning to add more.
This refactoring separate the minimum information for accessing the file. This object is copyable (FileMetaData is not copyable since the ref counter). I hope this refactoring can enable further improvements:

(1) use it to design a more efficient data structure to speed up read queries.
(2) in the future, when we add information of storage level, we can easily do the encoding, instead of enlarge this structure, which might expand memory work set for file meta data.

The definition is same as current EncodedFileMetaData used in two level iterator, so now the logic in two level iterator is easier to understand.

Test Plan: make all check

Reviewers: haobo, igor, ljin

Reviewed By: ljin

Subscribers: leveldb, dhruba, yhchiang

Differential Revision: https://reviews.facebook.net/D18933

Summary: Provide an convenience option to create column families if they are missing from the DB. Task #4460490

Test Plan: added unit test. also, stress test for some time

Reviewers: sdong, haobo, dhruba, ljin, yhchiang

Reviewed By: yhchiang

Subscribers: yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D18951

Summary: We have a perf regression of Write() even with one column family. Make fast path for single column family to avoid the perf regression. See task #4455480

Test Plan: make check

Reviewers: sdong, ljin

Reviewed By: sdong, ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D18963

Summary: In universal compaction, MaxFileSizeForLevel is ULLONG_MAX. We've been preallocation files to UULONG_MAX size all these time :)

Test Plan: make check

Reviewers: dhruba, haobo, ljin, sdong, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D18915

Summary: https://phabricator.fb.com/P11372644

Test Plan: compiles

Reviewers: sdong, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D18873

Summary:
In this patch, try to allocate the whole iterator tree starting from DBIter from an arena
1. ArenaWrappedDBIter is created when serves as the entry point of an iterator tree, with an arena in it.
2. Add an option to create iterator from arena for following iterators: DBIter, MergingIterator, MemtableIterator, all mem table's iterators, all table reader's iterators and two level iterator.
3. MergeIteratorBuilder is created to incrementally build the tree of internal iterators. It is passed to mem table list and version set and add iterators to it.

Limitations:
(1) Only DB::NewIterator() without tailing uses the arena. Other cases, including readonly DB and compactions are still from malloc
(2) Two level iterator itself is allocated in arena, but not iterators inside it.

Test Plan: make all check

Reviewers: ljin, haobo

Reviewed By: haobo

Subscribers: leveldb, dhruba, yhchiang, igor

Differential Revision: https://reviews.facebook.net/D18513

Summary:
At the end of BackgroundCallCompaction(), we call SignalAll(), even though we don't need to. If compaction hasn't done anything and there's another compaction running, there is no need to signal on the condition variable. Doing so creates a tight feedback loop which results in log files like:

   wait for memtable flush
   compaction nothing to do
   wait for memtable flush
   compaction nothing to do

This change eliminates that

Test Plan:
make check
Also:

    icanadi@dev1440 ~ $ grep "nothing to do" /fast-rocksdb-tmp/rocksdb_test/column_family_test/LOG | wc -l
    7435
    icanadi@dev1440 ~ $ grep "nothing to do" /fast-rocksdb-tmp/rocksdb_test/column_family_test/LOG | wc -l
    372

First version is before the change, second version is after the change.

Reviewers: dhruba, ljin, haobo, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D18855

Summary:
We've seen some production issues where column family is detected as stale, although there is only one column family in the system. This is a quick fix that:
1) doesn't flush stale column families if there's only one of them
2) Use 4 as a coefficient instead of 2 for determening when a column family is stale. This will make flushing less aggressive, while still keep a nice dynamic flushing of very stale CFs.

Test Plan: make check

Reviewers: dhruba, haobo, ljin, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D18861

Summary:
Forward iterator puts everything together in a flat structure instead of
a hierarchy of nested iterators. this should simplify the code and
provide better performance. It also enables more optimization since all
information are accessiable in one place.
Init evaluation shows about 6% improvement

Test Plan: db_test and db_bench

Reviewers: dhruba, igor, tnovak, sdong, haobo

Reviewed By: haobo

Subscribers: sdong, leveldb

Differential Revision: https://reviews.facebook.net/D18795

Summary:
Introducing new compaction style -- FIFO.

FIFO compaction style has write amplification of 1 (+1 for WAL) and it deletes the oldest files when the total DB size exceeds pre-configured values.

FIFO compaction style is suited for storing high-frequency event logs.

Test Plan: Added a unit test

Reviewers: dhruba, haobo, sdong

Reviewed By: dhruba

Subscribers: alberts, leveldb

Differential Revision: https://reviews.facebook.net/D18765

Summary:
Fixed a file-not-found issue when a log file is moved to archive
by doing a missing retry.

Test Plan:
make db_test
export ROCKSDB_TEST=TransactionLogIteratorRace
./db_test

Reviewers: sdong, haobo

Reviewed By: sdong

CC: igor, leveldb

Differential Revision: https://reviews.facebook.net/D18669

Summary: One of our users reported current file corruption. The machine was rebooted during the time. This is the only think I can think of which could cause current file corruption. Just add this paranoid check.

Test Plan: make all check

Reviewers: haobo, igor

Reviewed By: haobo

CC: yhchiang, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D18495

Summary:
Added a new option `max_total_wal_size`. Once the total WAL size goes over that, we make an attempt to flush all column families that still have data in the earliest WAL file.

By default, I calculate `max_total_wal_size` dynamically, that should be good-enough for non-advanced customers.

Test Plan: Added a test

Reviewers: dhruba, haobo, sdong, ljin, yhchiang

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18345

Summary:
= Major Changes =
* Add a new mem-table representation, HashCuckooRep, which is based cuckoo hash.
  Cuckoo hash uses multiple hash functions.  This allows each key to have multiple
  possible locations in the mem-table.

  - Put: When insert a key, it will try to find whether one of its possible
    locations is vacant and store the key.  If none of its possible
    locations are available, then it will kick out a victim key and
    store at that location.  The kicked-out victim key will then be
    stored at a vacant space of its possible locations or kick-out
    another victim.  In this diff, the kick-out path (known as
    cuckoo-path) is found using BFS, which guarantees to be the shortest.

 - Get: Simply tries all possible locations of a key --- this guarantees
   worst-case constant time complexity.

 - Time complexity: O(1) for Get, and average O(1) for Put if the
   fullness of the mem-table is below 80%.

 - Default using two hash functions, the number of hash functions used
   by the cuckoo-hash may dynamically increase if it fails to find a
   short-enough kick-out path.

 - Currently, HashCuckooRep does not support iteration and snapshots,
   as our current main purpose of this is to optimize point access.

= Minor Changes =
* Add IsSnapshotSupported() to DB to indicate whether the current DB
  supports snapshots.  If it returns false, then DB::GetSnapshot() will
  always return nullptr.

Test Plan:
Run existing tests.  Will develop a test specifically for cuckoo hash in
the next diff.

Reviewers: sdong, haobo

Reviewed By: sdong

CC: leveldb, dhruba, igor

Differential Revision: https://reviews.facebook.net/D16155

Summary:
ReadFirstRecord() reads the actual log file from disk on every call. This diff introduces a cache layer on top of ReadFirstRecord(), which should significantly speed up repeated calls to GetUpdatesSince().

I also cleaned up some stuff, but the whole TransactionLogIterator could use some refactoring, especially if we see increased usage.

Test Plan: make check

Reviewers: haobo, sdong, dhruba

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18387

Summary:
also add an override option total_order_iteration if you want to use full
iterator with prefix_extractor

Test Plan: make all check

Reviewers: igor, haobo, sdong, yhchiang

Reviewed By: haobo

CC: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D17805

Summary: As summary. Add two autovectors that get filled up in MakeRoomForWrite and they get deleted outside of mutex

Test Plan: make check

Reviewers: dhruba, haobo, ljin, sdong

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18249

Summary:
Now that we have column families involved, we need to add extra context to every log message. They now start with "[column family name] log message"

Also added some logging that I think would be useful, like level summary after every flush (I often needed that when going through the logs).

Test Plan: make check + ran db_bench to confirm I'm happy with log output

Reviewers: dhruba, haobo, ljin, yhchiang, sdong

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18303

Summary:
One of our profilings shows that Version::Get() sometimes is slow when getting pointer of user comparators or other global objects. In this patch:
(1) we keep pointers of immutable objects in Version to avoid accesses them though option objects or cfd objects
(2) table_reader is directly cached in FileMetaData so that table cache don't have to go through handle first to fetch it
(3) If level 0 has less than 3 files, skip the filtering logic based on SST tables' key range. Smallest and largest key are stored in separated memory locations, which has potential cache misses

Test Plan: make all check

Reviewers: haobo, ljin

Reviewed By: haobo

CC: igor, yhchiang, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D17739

Summary: Current behavior of creating new DB is, if there is existing log files, we will go ahead and replay them on top of empty DB. This is a behavior that no user would expect. With this patch, we will fail the creation if a user creates a DB with existing log files.

Test Plan: make all check

Reviewers: haobo, igor, ljin

Reviewed By: haobo

CC: nkg-, yhchiang, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D17817

Summary:
Introducing RocksDBLite! Removes all the non-essential features and reduces the binary size. This effort should help our adoption on mobile.

Binary size when compiling for IOS (`TARGET_OS=IOS m static_lib`) is down to 9MB from 15MB (without stripping)

Test Plan: compiles :)

Reviewers: dhruba, haobo, ljin, sdong, yhchiang

Reviewed By: yhchiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17835

Summary:
With multiple column families, especially when manual Flush is executed, we might roll the log file, although the current log file is empty (no data has been written to the log).

After the diff, we won't create new log file if current is empty.

Next, I will write an algorithm that will flush column families that reference old log files (i.e., that weren't flushed in a while)

Test Plan: Added an unit test. Confirmed that unit test failes in master

Reviewers: dhruba, haobo, ljin, sdong

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17631

Summary:
replace the super version acquisision in tailing itrator with thread
local

Test Plan: will post results

Reviewers: igor, haobo, sdong, yhchiang, dhruba

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17757

Summary:
Similar to GetImp(), use SuperVersion from thread local instead of acquriing mutex.
I don't expect this change will make a dent on NewIterator() performance
because the bottleneck seems to be on the rest part of the API

Test Plan:
make asan_check
will post perf numbers

Reviewers: haobo, igor, sdong, dhruba, yhchiang

Reviewed By: sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17643

Summary: XCode for some reason injects `#define DEBUG 1` into our code, which makes compile fail because we use `DEBUG` keyword for other stuff. This diff fixes the issue by renaming `DEBUG` to `DEBUG_LEVEL`.

Test Plan: compiles

Reviewers: dhruba, haobo, sdong, yhchiang, ljin

Reviewed By: yhchiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17709

Summary:
1. Polish IterKey a little bit.
2. Turn to use it in local parameter of current_user_key in DBImpl::ProcessKeyValueCompaction(). Our profile showing that DBImpl::ProcessKeyValueCompaction() has about 14% costs in std::string (the base including reading and writing data but excluding compaction filtering), which is higher than it should be. There are two std::string used in DBImpl::ProcessKeyValueCompaction(), compaction_filter_value and current_user_key and it's hard to distinguish the two.

Test Plan: make all check

Reviewers: haobo, ljin

Reviewed By: haobo

CC: igor, yhchiang, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D17613

Summary: When opening DB in read-only mode, client can choose to only specify a subset of column families ("default" column family can't be omitted, though)

Test Plan: added a unit test in column_family_test

Reviewers: haobo, sdong, ljin, dhruba

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17565

Summary: env_ is not used. Compiling for iOS complains.

Test Plan: compiles now

Reviewers: ljin, haobo, sdong, dhruba

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17589

Summary: ToString() is expensive. Profiling shows that most compaction threads are stuck in jemalloc, allocating a new string. This will help out a litte.

Test Plan: make check

Reviewers: haobo, danguo

Reviewed By: danguo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17583

Summary: This will allow us to disable them completely for iOS or for better performance

Test Plan: will run make all check

Reviewers: igor, haobo, dhruba

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17511