Re: sync()

Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Tatsuo Ishii wrote:
>> Can someone tell me why we need sync() here?

> As part of checkpoint, we discard some WAL files.  To do that, we must
> first be sure that all the dirty buffers we have written to the kernel
> are actually on the disk.  That is why the sync() is required.

What we really need is something better than sync(), viz flush all dirty
buffers to disk *and* wait till they're written.  But sync() and sleep
for awhile is the closest portable approximation.
        regards, tom lane