Summary:
There is a new option called hybrid_mode which, when switched on,
causes HBase style compactions. Files from L0 are
compacted back into L0. This meat of this compaction algorithm
is in PickCompactionHybrid().
All files reside in L0. That means all files have overlapping
keys. Each file has a time-bound, i.e. each file contains a
range of keys that were inserted around the same time. The
start-seqno and the end-seqno refers to the timeframe when
these keys were inserted. Files that have contiguous seqno
are compacted together into a larger file. All files are
ordered from most recent to the oldest.
The current compaction algorithm starts to look for
candidate files starting from the most recent file. It continues to
add more files to the same compaction run as long as the
sum of the files chosen till now is smaller than the next
candidate file size. This logic needs to be debated
and validated.
The above logic should reduce write amplification to a
large extent... will publish numbers shortly.
Test Plan: dbstress runs for 6 hours with no data corruption (tested so far).
Differential Revision: https://reviews.facebook.net/D11289
Summary:
This diff simplifies EnvOptions by treating it as POD, similar to Options.
- virtual functions are removed and member fields are accessed directly.
- StorageOptions is removed.
- Options.allow_readahead and Options.allow_readahead_compactions are deprecated.
- Unused global variables are removed: useOsBuffer, useFsReadAhead, useMmapRead, useMmapWrite
Test Plan: make check; db_stress
Reviewers: dhruba
CC: leveldb
Differential Revision: https://reviews.facebook.net/D11175
Summary:
This patch allows an application to specify whether to use bufferedio,
reads-via-mmaps and writes-via-mmaps per database. Earlier, there
was a global static variable that was used to configure this functionality.
The default setting remains the same (and is backward compatible):
1. use bufferedio
2. do not use mmaps for reads
3. use mmap for writes
4. use readaheads for reads needed for compaction
I also added a parameter to db_bench to be able to explicitly specify
whether to do readaheads for compactions or not.
Test Plan: make check
Reviewers: sheki, heyongqiang, MarkCallaghan
Reviewed By: sheki
CC: leveldb
Differential Revision: https://reviews.facebook.net/D9429
Summary:
Rocks accumulates recent writes and deletes in the in-memory memtable.
When the memtable is full, it writes the contents on the memtable to
a file in L0.
This patch removes redundant records at the time of the flush. If there
are multiple versions of the same key in the memtable, then only the
most recent one is dumped into the output file. The purging of
redundant records occur only if the most recent snapshot is earlier
than the earliest record in the memtable.
Should we switch on this feature by default or should we keep this feature
turned off in the default settings?
Test Plan: Added test case to db_test.cc
Reviewers: sheki, vamsi, emayanke, heyongqiang
Reviewed By: sheki
CC: leveldb
Differential Revision: https://reviews.facebook.net/D8991
Summary:
Replace manual memory management with std::unique_ptr in a
number of places; not exhaustive, but this fixes a few leaks with file
handles as well as clarifies semantics of the ownership of file handles
with log classes.
Test Plan: db_stress, make check
Reviewers: dhruba
Reviewed By: dhruba
CC: zshao, leveldb, heyongqiang
Differential Revision: https://reviews.facebook.net/D8043
published in https://reviews.facebook.net/D5997.
Summary:
This patch allows compaction to occur in multiple background threads
concurrently.
If a manual compaction is issued, the system falls back to a
single-compaction-thread model. This is done to ensure correctess
and simplicity of code. When the manual compaction is finished,
the system resumes its concurrent-compaction mode automatically.
The updates to the manifest are done via group-commit approach.
Test Plan: run db_bench
In particular, we add a new FilterPolicy class. An instance
of this class can be supplied in Options when opening a
database. If supplied, the instance is used to generate
summaries of keys (e.g., a bloom filter) which are placed in
sstables. These summaries are consulted by DB::Get() so we
can avoid reading sstable blocks that are guaranteed to not
contain the key we are looking for.
This change provides one implementation of FilterPolicy
based on bloom filters.
Other changes:
- Updated version number to 1.4.
- Some build tweaks.
- C binding for CompactRange.
- A few more benchmarks: deleteseq, deleterandom, readmissing, seekrandom.
- Minor .gitignore update.
- Replace raw slice comparison with a call to user comparator.
Added test for custom comparators.
- Fix end of namespace comments.
- Fixed bug in picking inputs for a level-0 compaction.
When finding overlapping files, the covered range may expand
as files are added to the input set. We now correctly expand
the range when this happens instead of continuing to use the
old range. For example, suppose L0 contains files with the
following ranges:
F1: a .. d
F2: c .. g
F3: f .. j
and the initial compaction target is F3. We used to search
for range f..j which yielded {F2,F3}. However we now expand
the range as soon as another file is added. In this case,
when F2 is added, we expand the range to c..j and restart the
search. That picks up file F1 as well.
This change fixes a bug related to deleted keys showing up
incorrectly after a compaction as described in Issue 44.
(Sync with upstream @25072954)
- Removed one copy of an uncompressed block contents changing
the signature of Snappy_Uncompress() so it uncompresses into a
flat array instead of a std::string.
Speeds up readrandom ~10%.
- Instead of a combination of Env/WritableFile, we now have a
Logger interface that can be easily overridden applications
that want to supply their own logging.
- Separated out the gcc and Sun Studio parts of atomic_pointer.h
so we can use 'asm', 'volatile' keywords for Sun Studio.
git-svn-id: https://leveldb.googlecode.com/svn/trunk@39 62dab493-f737-651d-591e-8d6aee1b9529
- LevelDB patch for Sun Studio
Based on a patch submitted by Theo Schlossnagle - thanks!
This fixes Issue 17.
- Fix a couple of test related memory leaks.
git-svn-id: https://leveldb.googlecode.com/svn/trunk@38 62dab493-f737-651d-591e-8d6aee1b9529
- Implemented Get() directly instead of building on top of a full
merging iterator stack. This speeds up the "readrandom" benchmark
by up to 15-30%.
- Fixed an opensource compilation problem.
Added --db=<name> flag to control where the database is placed.
- Automatically compact a file when we have done enough
overlapping seeks to that file.
- Fixed a performance bug where we would read from at least one
file in a level even if none of the files overlapped the key
being read.
- Makefile fix for Mac OSX installations that have XCode 4 without XCode 3.
- Unified the two occurrences of binary search in a file-list
into one routine.
- Found and fixed a bug where we would unnecessarily search the
last file when looking for a key larger than all data in the
level.
- A fix to avoid the need for trivial move compactions and
therefore gets rid of two out of five syncs in "fillseq".
- Removed the MANIFEST file write when switching to a new
memtable/log-file for a 10-20% improvement on fill speed on ext4.
- Adding a SNAPPY setting in the Makefile for folks who have
Snappy installed. Snappy compresses values and speeds up writes.
git-svn-id: https://leveldb.googlecode.com/svn/trunk@32 62dab493-f737-651d-591e-8d6aee1b9529
* env_chromium.cc should not export symbols.
* Fix MSVC warnings.
* Removed large value support.
* Fix broken reference to documentation file
git-svn-id: https://leveldb.googlecode.com/svn/trunk@24 62dab493-f737-651d-591e-8d6aee1b9529
Dhruba Borthakur