Revision 843738d8dcbf666701db265c2479827040c8b1d3 authored by sdong on 12 June 2018, 23:59:46 UTC, committed by sdong on 18 June 2018, 16:50:10 UTC
Summary:
A recent change pushed down the upper bound checking to child iterators. However, this causes the logic of following sequence wrong:
  Seek(key);
  if (!Valid()) SeekToLast();
Because !Valid() may be caused by upper bounds, rather than the end of the iterator. In this case SeekToLast() points to totally wrong places. This can cause wrong results, infinite loops, or segfault in some cases.
This sequence is called when changing direction from forward to backward. And this by itself also implicitly happen during reseeking optimization in Prev().

Fix this bug by using SeekForPrev() rather than this sequence, as what is already done in prefix extrator case.
Closes https://github.com/facebook/rocksdb/pull/3989

Differential Revision: D8385422

Pulled By: siying

fbshipit-source-id: 429e869990cfd2dc389421e0836fc496bed67bb4
1 parent cc0a65f
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