Re: [PATCH] Use access() to check file existence in GetNewRelFileNode(). - Mailing list pgsql-hackers

On Thu, May 17, 2018 at 04:09:27PM +0800, Paul Guo wrote:
> Previous code uses BasicOpenFile() + close().
>
> access() should be faster than BasicOpenFile()+close() and access()
> should be more correct since BasicOpenFile() could fail for various
> cases (e.g. due to file permission, etc) even the file exists.

Failing because of file permissions would be correct.  There have been
cases in the past, particularly on Windows, where anti-virus softwares
wildly scan files, causing EACCES on various points of the data folder.

> access() is supported on Linux/Unix. I do not have a Windows dev
> environment, but MSDN tells me that access() is supported on Windows also
> and there have been access() call in the workspace, so I assume there is no
> portability issue.

Yes, access() is spread already in the core code.

-    fd = BasicOpenFile(rpath, O_RDONLY | PG_BINARY);

-    if (fd >= 0)
+    if (access(rpath, F_OK) == 0)

What you are looking for here is R_OK, no?
--
Michael