Re: Performance patch for Win32

Mark Dilger <markdilger(at)yahoo(dot)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