Re: [HACKERS] Path-length follies

> Whilst cleaning up query-length dependencies, I noticed that our
> handling of maximum file pathname lengths is awfully messy.
> 
> Different parts of the system rely on no fewer than four different
> symbols that they import from several different system header
> files (any one of which might not exist on a particular platform):
>     MAXPATHLEN, _POSIX_PATH_MAX, MAX_PATH, PATH_MAX
> And on top of that, postgres.h defines MAXPGPATH which is used
> by yet other places.
> 
> On my system, _POSIX_PATH_MAX = 255, PATH_MAX = 1023, MAXPATHLEN = 1024
> (a nearby Linux box is almost but not quite the same) whereas MAXPGPATH
> is 128.  So there is absolutely no consistency to the pathname length
> limits being imposed in different parts of Postgres.
> 
> AFAIK, most or all flavors of Unix have kernel limits on the maximum
> length of a pathname that will be accepted by the kernel's file-access
> calls (it's 1024 on my box).  So I don't feel any need to remove
> hardwired limits on pathname lengths in favor of indefinitely-expansible
> buffers.  But it does seem that a little more consistency in the
> hardwired limits is called for.
> 
> >From the information I have, it seems that the various allegedly-
> standard #defines for max pathname length are not too standard,
> and I don't think that Postgres internal buffers ought to constrain
> path lengths to much less than the kernel limit (so using the
> seemingly "standard" _POSIX_PATH_MAX symbol would be a loser).
> So my inclination is to define MAXPGPATH as 1024 in config.h, and
> remove all uses of the other four symbols in favor of MAXPGPATH.
> That would at least provide a single point of tweaking for anyone
> who didn't like the value of 1024.
> 
> Does anyone have a better idea?  Is it worth trying to extract a
> system limit on pathlength during configure, rather than leaving
> MAXPGPATH as a manual configuration item --- and if so, exactly how
> should configure go about it?

I don't like the 128 or 256 numbers, but isn't there a predefined place
for this value in standard system headers?


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