pgbench reports its progress of loading ("N tuples done.") or vacuuming
("vacuum...end"), but the messages are not printed on the moment on mingw.
The reason seems to be the buffering of stderr. This patch adds fflush()
just after each fprintf(stderr).
The buffered stderr might be a bug of mingw, but redundant fflush()
does not make mischief for platforms that have correct stderr.
Regards,
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ITAGAKI Takahiro
NTT Open Source Software Center