Re: SRA Win32 sync() code

Bruce Momjian wrote:
> Here is the SRA sync() code for Win32.  As you might know, fsync on
> Win32 is _commit, and sync() is _flushall.  However, _flushall only
> flushes only _open_ kernel buffers, not dirty buffers that have been
> closed.  Therefore, on Win32, during checkpoint, you have to open,
> fsync(_commit), close all file that have been modified since the
> previous checkpoint.

That is not quite correct.  flushall() flushes all open file streams,
not open file 'handles' i.e. array references to _osfile[] returned by
_open().  flushall() is an aggregate fflush() command().  Note that this
is as implemented by Microsoft C runtime, not necessarily MinGW.  So,
when compiled with the ms C libraries, _flushall is useless.

A _handle based flushall routine would have to loop over the _osfile
array and commit file handles, or track them externally as SRA did.

What about rewriting the close routine to call FlushFileBuffers before
closing the file?  Would this break anything?

> Not sure how we are going to do this in Win32, but somehow we will
have
> to record all open files between checkpoints in an area that the
> checkpoint process can read during a checkpoint.

Iff the file handles can be reliably commited on closure this would not
be necessary.  The C runtime already keeps track of open files.

Merlin