Fix range tombstone covering short-circuit logic #4698
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Summary: Since a range tombstone seen at one level will cover all keys in the range at lower levels, there was a short-circuiting check in Get that reported a key was not found at most one file after the range tombstone was discovered. However, this was incorrect for merge operands, since a deletion might only cover some merge operands, which implies that the key should be found. This PR fixes this logic in the Version portion of Get, and removes the logic from the MemTable portion of Get, since the perforamnce benefit provided there is minimal. Test Plan: TEST_TMPDIR=/dev/shm python tools/db_crashtest.py blackbox --simple --delrangepercent=1 --delpercent=4 --write_buffer_size=1048576 --max_bytes_for_level_base=4194304 --target_file_size_base=1048576 --value_size_mult=33 --max_background_compactions=12 --max_key=10000000 --interval=30
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can you update "HISTORY.md" bug fix section? We should backport this to 5.18 too after you land it. |
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@abhimadan is landing this pull request. If you are a Facebook employee, you can view this diff on Phabricator.
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Summary: Since a range tombstone seen at one level will cover all keys
in the range at lower levels, there was a short-circuiting check in Get
that reported a key was not found at most one file after the range
tombstone was discovered. However, this was incorrect for merge
operands, since a deletion might only cover some merge operands,
which implies that the key should be found. This PR fixes this logic in
the Version portion of Get, and removes the logic from the MemTable
portion of Get, since the perforamnce benefit provided there is minimal.
Test Plan: TEST_TMPDIR=/dev/shm python tools/db_crashtest.py
blackbox --simple --delrangepercent=1 --delpercent=4
--write_buffer_size=1048576 --max_bytes_for_level_base=4194304
--target_file_size_base=1048576 --value_size_mult=33
--max_background_compactions=12 --max_key=10000000 --interval=30