Dhruba Borthakur
3754f2f4ff
A major bug that was not considering the compaction score of the n-1 level.
Summary:
The method Finalize() recomputes the compaction score of each
level and then sorts these score from largest to smallest. The
idea is that the level with the largest compaction score will
be a better candidate for compaction. There are usually very
few levels, and a bubble sort code was used to sort these
compaction scores. There existed a bug in the sorting code that
skipped looking at the score for the n-1 level. This meant that
even if the compaction score of the n-1 level is large, it will
not be picked for compaction.
This patch fixes the bug and also introduces "asserts" in the
code to detect any possible inconsistencies caused by future bugs.
This bug existed in the very first code change that introduced
multi-threaded compaction to the leveldb code. That version of
code was committed on Oct 19th via
1ca0584345
Test Plan: make clean check OPT=-g
Reviewers: emayanke, sheki, MarkCallaghan
Reviewed By: sheki
CC: leveldb
Differential Revision: https://reviews.facebook.net/D6837
leveldb: A key-value store Authors: Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com) The code under this directory implements a system for maintaining a persistent key/value store. See doc/index.html for more explanation. See doc/impl.html for a brief overview of the implementation. 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 internal APIs may be changed without warning. Guide to header files: include/db.h Main interface to the DB: Start here include/options.h Control over the behavior of an entire database, and also control over the behavior of individual reads and writes. 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.) include/iterator.h Interface for iterating over data. You can get an iterator from a DB object. include/write_batch.h Interface for atomically applying multiple updates to a database. include/slice.h A simple module for maintaining a pointer and a 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. include/env.h Abstraction of the OS environment. A posix implementation of this interface is in util/env_posix.cc include/table.h include/table_builder.h Lower-level modules that most clients probably won't use directly
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