Commit Graph

187 Commits

Author SHA1 Message Date
Jonah Cohen
a14b7873ee Enforce write buffer memory limit across column families
Summary:
Introduces a new class for managing write buffer memory across column
families.  We supplement ColumnFamilyOptions::write_buffer_size with
ColumnFamilyOptions::write_buffer, a shared pointer to a WriteBuffer
instance that enforces memory limits before flushing out to disk.

Test Plan: Added SharedWriteBuffer unit test to db_test.cc

Reviewers: sdong, rven, ljin, igor

Reviewed By: igor

Subscribers: tnovak, yhchiang, dhruba, xjin, MarkCallaghan, yoshinorim

Differential Revision: https://reviews.facebook.net/D22581
2014-12-02 12:09:20 -08:00
Yueh-Hsuan Chiang
4b63fcbff3 Add enable_thread_tracking to DBOptions
Summary:
Add enable_thread_tracking to DBOptions to allow
tracking thread status related to the DB.  Default is off.

Test Plan:
export ROCKSDB_TESTS=ThreadList
./db_test

Reviewers: ljin, sdong, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D29289
2014-11-20 21:13:18 -08:00
Igor Canadi
25f273027b Fix iOS compile with -Wshorten-64-to-32
Summary: So iOS size_t is 32-bit, so we need to static_cast<size_t> any uint64_t :(

Test Plan: TARGET_OS=IOS make static_lib

Reviewers: dhruba, ljin, yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D28743
2014-11-13 14:39:30 -05:00
Yueh-Hsuan Chiang
28c82ff1b3 CompactFiles, EventListener and GetDatabaseMetaData
Summary:
This diff adds three sets of APIs to RocksDB.

= GetColumnFamilyMetaData =
* This APIs allow users to obtain the current state of a RocksDB instance on one column family.
* See GetColumnFamilyMetaData in include/rocksdb/db.h

= EventListener =
* A virtual class that allows users to implement a set of
  call-back functions which will be called when specific
  events of a RocksDB instance happens.
* To register EventListener, simply insert an EventListener to ColumnFamilyOptions::listeners

= CompactFiles =
* CompactFiles API inputs a set of file numbers and an output level, and RocksDB
  will try to compact those files into the specified level.

= Example =
* Example code can be found in example/compact_files_example.cc, which implements
  a simple external compactor using EventListener, GetColumnFamilyMetaData, and
  CompactFiles API.

Test Plan:
listener_test
compactor_test
example/compact_files_example
export ROCKSDB_TESTS=CompactFiles
db_test
export ROCKSDB_TESTS=MetaData
db_test

Reviewers: ljin, igor, rven, sdong

Reviewed By: sdong

Subscribers: MarkCallaghan, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D24705
2014-11-07 14:45:18 -08:00
Lei Jin
f1841985e4 dynamic inplace_update options
Summary:
Make inplace_update_support and inplace_update_num_locks dynamic.
inplace_callback becomes immutable
We are almost free of references to cfd->options() in db_impl

Test Plan: unit test

Reviewers: igor, yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D25293
2014-10-27 12:10:13 -07:00
Lei Jin
5ec53f3edf make compaction related options changeable
Summary:
make compaction related options changeable. Most of changes are tedious,
following the same convention: grabs MutableCFOptions at the beginning
of compaction under mutex, then pass it throughout the job and register
it in SuperVersion at the end.

Test Plan: make all check

Reviewers: igor, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23349
2014-10-01 16:19:16 -07:00
Igor Canadi
21ddcf6e4f Remove allow_thread_local
Summary: See https://reviews.facebook.net/D19365

Test Plan: compiles

Reviewers: sdong, yhchiang, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23907
2014-09-24 13:12:16 -07:00
Lei Jin
0a29ce5393 re-enable BlockBasedTable::SetupForCompaction()
Summary:
It was commented out in D22545 by accident. Keep the option in
ImmutableOptions for now. I can make it dynamic in
https://reviews.facebook.net/D23349

Test Plan: make release

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23865
2014-09-23 14:18:57 -07:00
Lei Jin
57a32f147f change target_file_size_base to uint64_t
Summary: It contrains the file size to be 4G max with int

Test Plan:
tried to grep instance and made sure other related variables are also
uint64

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23697
2014-09-22 11:15:03 -07:00
Mark Callaghan
32f2532a0b Print compression_size_percent as a signed int
Summary:
compression_size_percent is an int but was printed as
an unsigned int. So the default of -1 is displayed as a big number.

Test Plan: make check

Reviewers: sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23679
2014-09-19 13:09:25 -07:00
Lei Jin
52311463e9 MemTableOptions
Summary: removed reference to options in WriteBatch and DBImpl::Get()

Test Plan: make all check

Reviewers: yhchiang, igor, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23049
2014-09-08 18:46:52 -07:00
Lei Jin
659d2d50c3 move compaction_filter to immutable_options
Summary:
all shared_ptrs are in immutable_options now. This will also make
options assignment a little cheaper

Test Plan: make release

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23001
2014-09-08 15:09:25 -07:00
Lei Jin
048560a642 reduce references to cfd->options() in DBImpl
Summary:
I found it is almost impossible to get rid of this function in a single
batch. I will take a step by step approach

Test Plan: make release

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D22995
2014-09-08 15:04:34 -07:00
liuhuahang
bb6ae0f80c fix more compile warnings
N/A

Change-Id: I5b6f9c70aea7d3f3489328834fed323d41106d9f
Signed-off-by: liuhuahang <liuhuahang@zerus.co>
2014-09-05 14:14:37 +08:00
Lei Jin
5665e5e285 introduce ImmutableOptions
Summary:
As a preparation to support updating some options dynamically, I'd like
to first introduce ImmutableOptions, which is a subset of Options that
cannot be changed during the course of a DB lifetime without restart.

ColumnFamily will keep both Options and ImmutableOptions. Any component
below ColumnFamily should only take ImmutableOptions in their
constructor. Other options should be taken from APIs, which will be
allowed to adjust dynamically.

I am yet to make changes to memtable and other related classes to take
ImmutableOptions in their ctor. That can be done in a seprate diff as
this one is already pretty big.

Test Plan: make all check

Reviewers: yhchiang, igor, sdong

Reviewed By: sdong

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D22545
2014-09-04 16:18:36 -07:00
Lei Jin
1755581f19 improve OptimizeForPointLookup()
Summary: also fix HISTORY.md

Test Plan: make all check

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D22437
2014-08-26 14:15:00 -07:00
Lei Jin
a98badff16 print table options
Summary: Add a virtual function in table factory that will print table options

Test Plan: make release

Reviewers: igor, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D22149
2014-08-25 14:24:09 -07:00
Lei Jin
384400128f move block based table related options BlockBasedTableOptions
Summary:
I will move compression related options in a separate diff since this
diff is already pretty lengthy.
I guess I will also need to change JNI accordingly :(

Test Plan: make all check

Reviewers: yhchiang, igor, sdong

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21915
2014-08-25 14:22:05 -07:00
Lei Jin
e91ebf1399 print compaction_filter name in Options.Dump
Summary:
Was looking at an issue. All options are the same except
compaction_filter was missed from a newer package. Our option dump does
not capture that

Test Plan: make release

Reviewers: sdong, igor, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21765
2014-08-13 15:58:31 -07:00
Lei Jin
5d0074c471 set bytes_per_sync to 1MB if rate limiter is enabled
Summary: as title

Test Plan: make all check

Reviewers: igor, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21201
2014-08-12 16:42:18 -07:00
Lei Jin
40fa8a4cd5 make statistics forward-able
Summary:
Make StatisticsImpl being able to forward stats to provided statistics
implementation. The main purpose is to allow us to collect internal
stats in the future even when user supplies custom statistics
implementation. It avoids intrumenting 2 sets of stats collection code.
One immediate use case is tuning advisor, which needs to collect some
internal stats, users may not be interested.

Test Plan:
ran db_bench and see stats show up at the end of run
Will run make all check since some tests rely on statistics

Reviewers: yhchiang, sdong, igor

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D20145
2014-07-28 12:05:36 -07:00
Igor Canadi
20c056306b Remove stats logger
Summary: Browsing through the code, looks like StatsLogger is not used at all!

Test Plan: compiles

Reviewers: ljin, sdong, yhchiang, dhruba

Reviewed By: dhruba

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D19827
2014-07-15 09:16:32 -04:00
Lei Jin
534357ca3a integrate rate limiter into rocksdb
Summary:
Add option and plugin rate limiter for PosixWritableFile. The rate
limiter only applies to flush and compaction. WAL and MANIFEST are
excluded from this enforcement.

Test Plan: db_test

Reviewers: igor, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19425
2014-07-08 12:31:49 -07:00
sdong
2459f7ec4e Support Multiple DB paths (without having an interface to expose to users)
Summary:
In this patch, we allow RocksDB to support multiple DB paths internally.
No user interface is supported yet so this patch is silent to users.

Test Plan: make all check

Reviewers: igor, haobo, ljin, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D18921
2014-07-02 21:14:44 -07:00
Yueh-Hsuan Chiang
81c5d98900 Fixed a comparison between signed and unsigned integers in options.cc
Summary:
Fixed the following warning:

util/options.cc: In constructor ‘rocksdb::ColumnFamilyOptions::ColumnFamilyOptions(const rocksdb::Options&)’:
util/options.cc:157:58: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
   if (max_bytes_for_level_multiplier_additional.size() < num_levels) {
                                                             ^

Test Plan: make all check

Reviewers: haobo, sdong, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19293
2014-06-25 15:31:30 -06:00
Yueh-Hsuan Chiang
55531fd089 Fixed heap-buffer-overflow issue when Options.num_levels > 7.
Summary:
Currently, when num_levels has been changed to > 7, internally
it will not resize max_bytes_for_level_multiplier_additional.
As a result, max_bytes_for_level_multiplier_additional.size() will
be smaller than num_levels, which causes heap-buffer-overflow.

Test Plan: make all check

Reviewers: haobo, sdong, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19275
2014-06-25 14:11:12 -06:00
Igor Canadi
d4a8423334 Remove seek compaction
Summary:
As discussed in our internal group, we don't get much use of seek compaction at the moment, while it's making code more complicated and slower in some cases.

This diff removes seek compaction and (hopefully) all code that was introduced to support seek compaction.

There is one test case that relied on didIO information. I'll try to find another way to implement it.

Test Plan: make check

Reviewers: sdong, haobo, yhchiang, ljin, dhruba

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19161
2014-06-20 10:23:02 +02:00
Igor Canadi
a0191c9dfe Create Missing Column Families
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
2014-06-06 18:04:56 -07:00
Igor Canadi
552c49f0f4 Remove upper bound for rate limiting unit test 2014-06-03 13:58:44 -07:00
Igor Canadi
6de6a06631 FIFO compaction style
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
2014-05-21 11:43:35 -07:00
Igor Canadi
26f5dd9a5a TablePropertiesCollectorFactory
Summary:
This diff addresses task #4296714 and rethinks how users provide us with TablePropertiesCollectors as part of Options.

Here's description of task #4296714:
       I'm debugging #4295529 and noticed that our count of user properties kDeletedKeys is wrong. We're sharing one single InternalKeyPropertiesCollector with all Table Builders. In LOG Files, we're outputting number of kDeletedKeys as connected with a single table, while it's actually the total count of deleted keys since creation of the DB.

       For example, this table has 3155 entries and 1391828 deleted keys.

The problem with current approach that we call methods on a single TablePropertiesCollector for all the tables we create. Even worse, we could do it from multiple threads at the same time and TablePropertiesCollector has no way of knowing which table we're calling it for.

Good part: Looks like nobody inside Facebook is using Options::table_properties_collectors. This means we should be able to painfully change the API.

In this change, I introduce TablePropertiesCollectorFactory. For every table we create, we call `CreateTablePropertiesCollector`, which creates a TablePropertiesCollector for a single table. We then use it sequentially from a single thread, which means it doesn't have to be thread-safe.

Test Plan:
Added a test in table_properties_collector_test that fails on master (build two tables, assert that kDeletedKeys count is correct for the second one).
Also, all other tests

Reviewers: sdong, dhruba, haobo, kailiu

Reviewed By: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18579
2014-05-13 12:30:55 -07:00
Igor Canadi
038a477b53 Make it easier to start using RocksDB
Summary:
This diff is addressing multiple things with a single goal -- to make RocksDB easier to use:
* Add some functions to Options that make RocksDB easier to tune.
* Add example code for both simple RocksDB and RocksDB with Column Families.
* Rewrite our README.md

Regarding Options, I took a stab at something we talked about for a long time:
* https://www.facebook.com/groups/rocksdb.dev/permalink/563169950448190/

I added functions:
* IncreaseParallelism() -- easy, increases the thread pool and max_background_compactions
* OptimizeLevelStyleCompaction(memtable_memory_budget) -- the easiest way to optimize rocksdb for less stalls with level style compaction. This is very likely not ideal configuration. Feel free to suggest improvements. I used some of Mark's suggestions from here: https://github.com/facebook/rocksdb/issues/54
* OptimizeUniversalStyleCompaction(memtable_memory_budget) -- optimize for universal compaction.

Test Plan: compiled rocksdb. ran examples.

Reviewers: dhruba, MarkCallaghan, haobo, sdong, yhchiang

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18621
2014-05-10 10:49:33 -07:00
sdong
4a7c747064 Revert "Revert "Allow allocating dynamic bloom, plain table indexes and hash linked list from huge page TLB""
And make the default 0 for hash linked list memtable

This reverts commit d69dc64be7.
2014-05-04 13:56:29 -07:00
Igor Canadi
d69dc64be7 Revert "Allow allocating dynamic bloom, plain table indexes and hash linked list from huge page TLB"
This reverts commit 7dafa3a1d7.
2014-05-04 08:37:09 -07:00
Igor Canadi
df70047669 Flush stale column families
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
2014-04-30 14:33:40 -04:00
sdong
7dafa3a1d7 Allow allocating dynamic bloom, plain table indexes and hash linked list from huge page TLB
Summary: Add an option to allocate a piece of memory from huge page TLB. Add options to trigger it in dynamic bloom, plain table indexes andhash linked list hash table.

Test Plan: make all check

Reviewers: haobo, ljin

Reviewed By: haobo

CC: nkg-, dhruba, leveldb, igor, yhchiang

Differential Revision: https://reviews.facebook.net/D18357
2014-04-30 11:02:26 -07:00
Igor Canadi
ddef6841b3 Renamed InfoLogLevel::DEBUG to InfoLogLevel::DEBUG_LEVEL
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
2014-04-10 15:27:42 -07:00
Igor Canadi
a4d73ddee0 Initialize Options::bloom_locality
Summary: I think this issue was caused by bad merge. We have to initialize bloom_locality, otherwise valgrind complains: "Use of uninitialised value of size 8"

Test Plan: Run valgrind ./prefix_test

Reviewers: ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17553
2014-04-07 16:33:03 -07:00
Igor Canadi
ddbd1ece88 Merge branch 'master' into columnfamilies
Conflicts:
	db/db_impl.cc
	db/db_test.cc
	db/internal_stats.cc
	db/internal_stats.h
	db/version_edit.cc
	db/version_edit.h
	db/version_set.cc
	include/rocksdb/options.h
	util/options.cc
2014-03-31 13:39:24 -07:00
sdong
43a593a6d9 Change default value of some Options
Summary: Since we are optimizing for server workloads, some default values are not optimized any more. We change some of those values that I feel it's less prone to regression bugs.

Test Plan: make all check

Reviewers: dhruba, haobo, ljin, igor, yhchiang

Reviewed By: igor

CC: leveldb, MarkCallaghan

Differential Revision: https://reviews.facebook.net/D16995
2014-03-28 17:09:28 -07:00
Lei Jin
0d755fff14 cache friendly blocked bloomfilter
Summary:
By constraining the probes within cache line(s), we can improve the
cache miss rate thus performance. This probably only makes sense for
in-memory workload so defaults the option to off.

Numbers and comparision can be found in wiki:
https://our.intern.facebook.com/intern/wiki/index.php/Ljin/rocksdb_perf/2014_03_17#Bloom_Filter_Study

Test Plan: benchmarked this change substantially. Will run make all check as well

Reviewers: haobo, igor, dhruba, sdong, yhchiang

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17133
2014-03-28 09:21:20 -07:00
Igor Canadi
b14c1f995b allow mmap writes 2014-03-27 12:00:38 -07:00
Igor Canadi
5826f9528f Make rate limiting unit test more robust 2014-03-27 11:53:05 -07:00
Igor Canadi
1c9f8f0884 Fix valgrind issues
Summary:
NewFixedPrefixTransform is leaked in default options. Broken by b47812fba6

Also included in the diff some code cleanup

Test Plan:
valgrind env_test
also make check

Reviewers: haobo, danguo, yhchiang

Reviewed By: danguo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17211
2014-03-27 08:22:59 -07:00
Igor Canadi
e8168382c4 Merge branch 'master' into columnfamilies
Conflicts:
	db/db_impl.cc
	include/rocksdb/options.h
	util/options.cc
2014-03-25 11:09:40 -07:00
Danny Guo
b47812fba6 [rocksdb] new CompactionFilterV2 API
Summary:
This diff adds a new CompactionFilterV2 API that roll up the
decisions of kv pairs during compactions. These kv pairs must share the
same key prefix. They are buffered inside the db.

    typedef std::vector<Slice> SliceVector;
    virtual std::vector<bool> Filter(int level,
                                 const SliceVector& keys,
                                 const SliceVector& existing_values,
                                 std::vector<std::string>* new_values,
                                 std::vector<bool>* values_changed
                                 ) const = 0;

Application can override the Filter() function to operate
on the buffered kv pairs. More details in the inline documentation.

Test Plan:
make check. Added unit tests to make sure Keep, Delete,
Change all works.

Reviewers: haobo

CCs: leveldb

Differential Revision: https://reviews.facebook.net/D15087
2014-03-24 20:47:53 -07:00
Yueh-Hsuan Chiang
cda4006e87 Enhance partial merge to support multiple arguments
Summary:
* PartialMerge api now takes a list of operands instead of two operands.
* Add min_pertial_merge_operands to Options, indicating the minimum
  number of operands to trigger partial merge.
* This diff is based on Schalk's previous diff (D14601), but it also
  includes necessary changes such as updating the pure C api for
  partial merge.

Test Plan:
* make check all
* develop tests for cases where partial merge takes more than two
  operands.

TODOs (from Schalk):
* Add test with min_partial_merge_operands > 2.
* Perform benchmarks to measure the performance improvements (can probably
  use results of task #2837810.)
* Add description of problem to doc/index.html.
* Change wiki pages to reflect the interface changes.

Reviewers: haobo, igor, vamsi

Reviewed By: haobo

CC: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D16815
2014-03-24 17:57:13 -07:00
Igor Canadi
9634ba42ac Merge branch 'master' into columnfamilies
Conflicts:
	db/compaction_picker.cc
	db/db_impl.cc
	db/db_impl.h
	db/tailing_iter.cc
	db/version_set.h
	include/rocksdb/options.h
	util/options.cc
2014-03-10 17:26:09 -07:00
Igor Canadi
04d2c26e17 Add option verify_checksums_in_compaction
Summary:
If verify_checksums_in_compaction is true, compaction will verify checksums. This is default.
If it's false, compaction doesn't verify checksums. This is useful for in-memory workloads.

Test Plan: corruption_test

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16695
2014-03-10 10:06:34 -07:00
Igor Canadi
80a207fc90 Merge branch 'master' into columnfamilies
Conflicts:
	db/compaction_picker.cc
	db/compaction_picker.h
	db/db_impl.cc
	db/version_set.cc
	db/version_set.h
	include/rocksdb/options.h
	util/options.cc
2014-03-05 16:59:22 -08:00