Re: sync()

Tatsuo Ishii wrote:
> I noticed sync() is used in PostgreSQL.
> 
> CHECKPOINT -> FlushBufferPool() -> smgrsync() -> mdsync() -> sync()
> 
> 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.

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