flush_job: do not roll back memtable flush on CF drop and DB shutdown (#126) #127
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udi-speedb
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Aug 21, 2022
…#126) Rolling back in these cases is meaningless because the memtables will be freed shortly afterwards, so making them available for flush again is useless at best. Additionally, in atomic flush, memtables that were successfully flushed aren't rolled back if a CF is dropped or a DB shutdown was requested (the shutdown case is the more relevant one for the comparison here because it aborts the flush, whereas the in the CF drop case it's simply ignored at flush result installation time). In this regard this change simply matches the behaviour there. Lastly, this might be needed for the WriteBufferManager changes in #113, since we plan to use the information about memory that can be flushed in the future for triggering flushes based on immutable memory as well, and rolling back flushes causes the memtable memory to become ready for flush again for a brief period of time until it is dropped, which might wrongly affect the WBM decisions.
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Rolling back in these cases is meaningless because the memtables will be
freed shortly afterwards, so making them available for flush again is useless
at best.
Additionally, in atomic flush, memtables that were successfully flushed
aren't rolled back if a CF is dropped or a DB shutdown was requested (the
shutdown case is the more relevant one for the comparison here because it
aborts the flush, whereas the in the CF drop case it's simply ignored at
flush result installation time). In this regard this change simply matches
the behaviour there.
Lastly, this might be needed for the WriteBufferManager changes in #113,
since we plan to use the information about memory that can be flushed in
the future for triggering flushes based on immutable memory as well, and
rolling back flushes causes the memtable memory to become ready for flush
again for a brief period of time until it is dropped, which might wrongly
affect the WBM decisions.
Test plan: run
make checkas well asmake crash_test.