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WritePrepared: relax assert in compaction iterator (#4969)

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Summary:
If IsInSnapshot(seq2, snapshot) determines that the snapshot is released, the future queries IsInSnapshot(seq1, snapshot) could still return a definitive answer of true if for example seq1 is too old that is determined visible in all snapshots. This violates a recently added assert statement to compaction iterator. The patch relaxes the assert.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4969

Differential Revision: D14030998

Pulled By: maysamyabandeh

fbshipit-source-id: 6db53db0e37d0a20e8997ef2c1004b8627614ab9
This commit is contained in:
Maysam Yabandeh 2019-02-11 14:56:50 -08:00 committed by Facebook Github Bot
parent 1218704b61
commit 576d2d6c60
1 changed files with 5 additions and 2 deletions
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7
db/compaction_iterator.cc
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@ -482,11 +482,14 @@ void CompactionIterator::NextFromInput() {
// this value, and findEarliestVisibleSnapshot returns the next snapshot
// as current_user_key_snapshot. In this case last value and current
// value are both in current_user_key_snapshot currently.
// Although last_snapshot is released we might still get a definitive
// response when key sequence number changes, e.g., when seq is determined
// too old and visible in all snapshots.
assert(last_snapshot == current_user_key_snapshot_ ||
(snapshot_checker_ != nullptr &&
snapshot_checker_->CheckInSnapshot(current_user_key_sequence_,
last_snapshot) ==
SnapshotCheckerResult::kSnapshotReleased));
last_snapshot) !=
SnapshotCheckerResult::kNotInSnapshot));
++iter_stats_.num_record_drop_hidden; // (A)
input_->Next();