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由 Levi Tamasi 提交于
Summary: Currently, when the block cache is used for index blocks as well, it is not really the index block that is stored in the cache but an IndexReader object. Since this object is not pure data (it has, for instance, pointers that might dangle), it's not really sharable. To avoid the issues around this, the current code uses a dummy unique cache key for each TableReader to store the IndexReader, and erases the IndexReader entry when the TableReader is closed. Instead of doing this, the new code moves the IndexReader out of the cache altogether. In particular, instead of the TableReader owning, or caching/pinning the IndexReader based on the customer's settings, the TableReader unconditionally owns the IndexReader, which in turn owns/caches/pins the index block (which is itself sharable and thus can be safely put in the cache without any hacks). Note: the change has two side effects: 1) Partitions of partitioned indexes no longer affect the read amplification statistics. 2) Eviction statistics for index blocks are temporarily broken. We plan to fix this in a separate phase. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5298 Differential Revision: D15303203 Pulled By: ltamasi fbshipit-source-id: 935a69ba59d87d5e44f42e2310619b790c366e47
1e355842
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