On Windows two tests fail that use MockTable:
flush_job_test and compaction_job_test with the following message:
compaction_job_test_je.exe : Assertion failed: result.size() == 4,
file c:\dev\rocksdb\rocksdb\table\mock_table.cc, line 110
Investigation reveals that this failure occurs when a 4 byte
ID written to a beginning of the physically open file (main
contents remains in a in-memory map) can not be read back.
The reason for the failure is that the ID is written directly
to a WritableFile bypassing WritableFileWriter. The side effect of that
is that pending_sync_ never becomes true so the file is never flushed,
however, the direct cause of the failure is that the filesize_ member
of the WritableFileWriter remains zero. At Close() the file is truncated
to that size and the file becomes empty so the ID can not be read back.
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