backport-19.2: storage: fix stats inconsistency due to WriteTooOld optimization #42148
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This fixes a bug introduced in cockroachdb#22315 with the introduction of a "local retry" to avoid WriteTooOldError inside of 1PC transactions that were not carrying out any reads. Such a transaction can simply be re-evaluated at a higher timestamp, which can allow it to commit. The bug was that when such a re-evaluation was carried out, we were not discarding the MVCCStats accrued from the first attempt. In effect, the request would thus be double-counted in stats, which would set off the consistency checker. The fix is easy: discard the delta before re-evaluating. Fixes cockroachdb#31870. Release note (bug fix): remove a source of (benign) stats inconsistencies (i.e. the stats of a range not accurately reflecting its contents).
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irfansharif
approved these changes
Nov 4, 2019
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Reviewed 2 of 2 files at r1.
Reviewable status:complete! 1 of 0 LGTMs obtained
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Backport 1/1 commits from #41986.
/cc @cockroachdb/release
This fixes a bug introduced in #22315 with the introduction of a "local
retry" to avoid WriteTooOldError inside of 1PC transactions that were
not carrying out any reads. Such a transaction can simply be
re-evaluated at a higher timestamp, which can allow it to commit.
The bug was that when such a re-evaluation was carried out, we were
not discarding the MVCCStats accrued from the first attempt. In
effect, the request would thus be double-counted in stats, which
would set off the consistency checker.
The fix is easy: discard the delta before re-evaluating.
Fixes #31870.
Release note (bug fix): remove a source of (benign) stats
inconsistencies (i.e. the stats of a range not accurately reflecting its
contents).