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@@ -16,7 +16,7 @@ Authors: Sanjay Ghemawat ([email protected]) and Jeff Dean ([email protected]) | |
* External activity (file system operations etc.) is relayed through a virtual interface so users can customize the operating system interactions. | ||
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# Documentation | ||
[LevelDB library documentation](https://rawgit.com/google/leveldb/master/doc/index.html) is online and bundled with the source code. | ||
[LevelDB library documentation](https://github.com/google/leveldb/blob/master/doc/index.md) is online and bundled with the source code. | ||
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# Limitations | ||
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@@ -113,29 +113,30 @@ by the one or two disk seeks needed to fetch the data from disk. | |
Write performance will be mostly unaffected by whether or not the | ||
working set fits in memory. | ||
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readrandom : 16.677 micros/op; (approximately 60,000 reads per second) | ||
readseq : 0.476 micros/op; 232.3 MB/s | ||
readreverse : 0.724 micros/op; 152.9 MB/s | ||
readrandom : 16.677 micros/op; (approximately 60,000 reads per second) | ||
readseq : 0.476 micros/op; 232.3 MB/s | ||
readreverse : 0.724 micros/op; 152.9 MB/s | ||
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LevelDB compacts its underlying storage data in the background to | ||
improve read performance. The results listed above were done | ||
immediately after a lot of random writes. The results after | ||
compactions (which are usually triggered automatically) are better. | ||
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readrandom : 11.602 micros/op; (approximately 85,000 reads per second) | ||
readseq : 0.423 micros/op; 261.8 MB/s | ||
readreverse : 0.663 micros/op; 166.9 MB/s | ||
readrandom : 11.602 micros/op; (approximately 85,000 reads per second) | ||
readseq : 0.423 micros/op; 261.8 MB/s | ||
readreverse : 0.663 micros/op; 166.9 MB/s | ||
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Some of the high cost of reads comes from repeated decompression of blocks | ||
read from disk. If we supply enough cache to the leveldb so it can hold the | ||
uncompressed blocks in memory, the read performance improves again: | ||
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readrandom : 9.775 micros/op; (approximately 100,000 reads per second before compaction) | ||
readrandom : 5.215 micros/op; (approximately 190,000 reads per second after compaction) | ||
readrandom : 9.775 micros/op; (approximately 100,000 reads per second before compaction) | ||
readrandom : 5.215 micros/op; (approximately 190,000 reads per second after compaction) | ||
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## Repository contents | ||
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See doc/index.html for more explanation. See doc/impl.html for a brief overview of the implementation. | ||
See [doc/index.md](doc/index.md) for more explanation. See | ||
[doc/impl.md](doc/impl.md) for a brief overview of the implementation. | ||
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The public interface is in include/*.h. Callers should not include or | ||
rely on the details of any other header files in this package. Those | ||
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* **include/options.h**: Control over the behavior of an entire database, | ||
and also control over the behavior of individual reads and writes. | ||
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* **include/comparator.h**: Abstraction for user-specified comparison function. | ||
* **include/comparator.h**: Abstraction for user-specified comparison function. | ||
If you want just bytewise comparison of keys, you can use the default | ||
comparator, but clients can write their own comparator implementations if they | ||
want custom ordering (e.g. to handle different character encodings, etc.) | ||
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@@ -165,7 +166,7 @@ length into some other byte array. | |
* **include/status.h**: Status is returned from many of the public interfaces | ||
and is used to report success and various kinds of errors. | ||
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* **include/env.h**: | ||
* **include/env.h**: | ||
Abstraction of the OS environment. A posix implementation of this interface is | ||
in util/env_posix.cc | ||
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