db: scan a readState during format major version upgrades #2186
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nicktrav
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Dec 20, 2022
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During a format major version, some version migrations must scan the LSM. These migrations require that the files they examine are not deleted before or while they're reading them. A previous attempt (cockroachdb#2020) at avoiding these unexpected deletions accidentally left an opening for the acquired versions' files to be deleted while waiting for file deletions to be disabled (sleeping on a condition variable). A different fix with less subtlety is applied here. The format major version upgrade path acquires a readState, which refs the versions it acquires, preventing deletion of the referenced files. This requires the format major version upgrade in Open to be moved later within the Open routine, after the current read state is initialized. Fix cockroachdb#2143.
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During a format major version, some version migrations must scan the LSM. These migrations require that the files they examine are not deleted before or while they're reading them. A previous attempt (#2020) at avoiding these unexpected deletions accidentally left an opening for the acquired versions' files to be deleted while waiting for file deletions to be disabled (sleeping on a condition variable).
A different fix with less subtlety is applied here. The format major version upgrade path acquires a readState, which refs the versions it acquires, preventing deletion of the referenced files. This requires the format major version upgrade in Open to be moved later within the Open routine, after the current read state is initialized.
Fix #2143.