Summary:
Somewhat confusingly, index and filter partition blocks are
never owned by table readers, even with
cache_index_and_filter_blocks=false. They still go into block cache
(possibly pinned by table reader) if there is a block cache. If no block
cache, they are only loaded transiently on demand.
This PR primarily clarifies the options APIs and some internal code
comments.
Also, this closes a hypothetical data corruption vulnerability where
some but not all index partitions are pinned. I haven't been able to
reproduce a case where it can happen (the failure seems to propagate
to abort table open) but it's worth patching nonetheless.
Fixes https://github.com/facebook/rocksdb/issues/8979
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9068
Test Plan:
existing tests :-/ I could cover the new code using sync
points, but then I'd have to very carefully relax my `assert(false)`
Reviewed By: ajkr
Differential Revision: D31898284
Pulled By: pdillinger
fbshipit-source-id: f2511a7d3a36bc04b627935d8e6cfea6422f98be
5bf9a7d5ee