Revision 9d9d2965cb4df6163624a31d2b5dd7364813f27f authored by Yueh-Hsuan Chiang on 30 April 2014, 00:13:46 UTC, committed by Yueh-Hsuan Chiang on 30 April 2014, 00:13:46 UTC
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
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File | Mode | Size |
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auto_sanity_test.sh | -rwxr-xr-x | 2.1 KB |
blob_store_bench.cc | -rw-r--r-- | 7.5 KB |
db_crashtest.py | -rw-r--r-- | 4.8 KB |
db_crashtest2.py | -rw-r--r-- | 5.7 KB |
db_repl_stress.cc | -rw-r--r-- | 4.0 KB |
db_sanity_test.cc | -rw-r--r-- | 5.5 KB |
db_stress.cc | -rw-r--r-- | 58.0 KB |
ldb.cc | -rw-r--r-- | 424 bytes |
ldb_test.py | -rw-r--r-- | 17.0 KB |
reduce_levels_test.cc | -rw-r--r-- | 4.9 KB |
sst_dump.cc | -rw-r--r-- | 10.8 KB |
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