[luatex] Can't open pipe in .tex doc

[Michael Talbot-Wilson]

On Tue, 14 Aug 2012, Michael Talbot-Wilson wrote:

> What I want is for my TeX document to read BLOBs (PDF images) and
> other stuff from a PostgreSQL database.  So "ls /" would become a psql
> (SQL) command.

Now I've noticed that the image_spec table requires a literal file
name, so that's the end of that idea.  You can't use an open file
descriptor so you can't use an open pipe descriptor.  The mapping's
key is explicitly "fllename", totally committed to it being restricted
to a name.

You can milk the named file with objnum but you can't refer to the
totality of it in a natural and flexible way.

I wonder what the reason is for that (to me) very serious restriction.
It seems totally unnecessary because lua does not need help to open a
file.

Am I missing something?  Is there a way around it?  ...named pipes?
...any other way?  Something in the registered callback department?
Anyone ever done such a basic thing?