release-22.2: storage: fix CheckSSTConflicts handling of MVCC range keys
#94115
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`CheckSSTConflicts` keeps an SST and engine iterator in sync while checking for conflicts. To avoid seek costs, it attempts to step the engine iterator in case the corresponding SST key is nearby. However, this stepping could step right past an MVCC range key overlapping the SST key, which would break conflict checks with MVCC range tombstones. This patch seeks the engine iterator back to the SST key if we step past it and the range key changed. Release note (bug fix): When experimental MVCC range tombstones are enabled (they're disabled by default), a bulk ingestion (e.g. an import) could in some situations fail to properly check for conflicts with existing MVCC range tombstones. This could cause the ingestion to write below a recently written MVCC range tombstone, in turn losing the ingested data. This could only happen in rare circumstances where a bulk ingestion was applied concurrently with an import cancellation.
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Backport 1/1 commits from #94045 on behalf of @erikgrinaker.
/cc @cockroachdb/release
CheckSSTConflictskeeps an SST and engine iterator in sync while checking for conflicts. To avoid seek costs, it attempts to step the engine iterator in case the corresponding SST key is nearby. However, this stepping could step right past an MVCC range key overlapping the SST key, which would break conflict checks with MVCC range tombstones.This patch seeks the engine iterator back to the SST key if we step past it and the range key changed.
Resolves #93968.
Release note (bug fix): When experimental MVCC range tombstones are enabled (they're disabled by default), a bulk ingestion (e.g. an import) could in some situations fail to properly check for conflicts with existing MVCC range tombstones. This could cause the ingestion to write below a recently written MVCC range tombstone, in turn losing the ingested data. This could only happen in rare circumstances where a bulk ingestion was applied concurrently with an import cancellation.
Release justification: fixes potential (but rare) data loss issue.