Re: Performance patch for Win32

On Tue, May 29, 2012 at 03:54:59PM -0700, Mark Dilger wrote:
> I was imagining that this would be a trap for linux developers
> who saw nothing wrong with their code until it made it to the
> build/test farm.  That's pretty far down the development
> process.  Of course, it is also a trap in the other direction, for
> Windows developers who use the pattern but do not include
> anything equivalent for the non-Windows execution path.
> 
> On the whole, however, your argument in favor of tighter
> patterns might be more convincing than my argument in favor
> of catching bugs sooner.
> 
> I will start implementing your suggestion for patch v2.

Any progress on this?

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> From: Tom Lane <tgl@sss.pgh.pa.us>
> To: Mark Dilger <markdilger@yahoo.com>
> Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
> Sent: Tuesday, May 29, 2012 3:42 PM
> Subject: Re: [HACKERS] Performance patch for Win32
> 
> Mark Dilger <markdilger@yahoo.com> writes:
> > I am hesitant to write a function like AllocateDirWithFilePattern
> > if the pattern is simply ignored on non-Windows.  In my patch,
> > the pattern underspecified the files, and the ad-hoc matching code
> > applied to all the returned files tightened that up.  But a person
> > could just as well overspecify the pattern and then they would get
> > different behavior on Windows vs. non-Windows, with fewer
> > files returned by FindNextFile() than would have matched the
> > ad-hoc pattern.
> 
> Well, if you're imagining that we wouldn't need to test carefully on
> both Windows and non-Windows, I think that's a pipe dream.  As an
> example, your proposal of AllocateDirWithFilePrefix would only work
> consistently across platforms if the prefix didn't contain anything
> that Windows thought was a pattern metacharacter.  (This might never
> come up, but I'm not too sure what the metacharacters are on Windows.)
> 
> Having said that, I have nothing particularly against the idea of
> specifying a prefix rather than an arbitrary pattern.  I'm just
> saying it'll still need testing.  Also, I wonder how many of the
> potential stat-equivalent operations we'll be unable to optimize
> away with the more restricted definition.  Using a tighter pattern
> on Windows seems basically free (modulo testing) if we accept that
> it's Windows-only.
> 
>             regards, tom lane
> 
> 

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
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