Re: Selecting a constant question

> -----Original Message-----
> From: Martijn van Oosterhout [mailto:kleptog@svana.org]
> Sent: Monday, June 11, 2007 3:29 PM
> To: Dann Corbit
> Cc: Alvaro Herrera; Gregory Stark; pgsql-hackers@postgresql.org; Larry
> McGhaw
> Subject: Re: [HACKERS] Selecting a constant question
>
> On Mon, Jun 11, 2007 at 03:18:33PM -0700, Dann Corbit wrote:
> > Sure, but when I bind to a grid, I need to know a-priori how big the
> > biggest returned instance can be.  Reading the entire data set twice
to
> > learn the size of a constant seems rather conceptually odd to me.
>
> To be honest, the concept that a widget requires a constant that can't
> be changed later is also a bit odd.

Not when the data itself is a constant that cannot be changed.

> There are many times you won't know
> beforehand how big the data is, surely the framework should be smart
> enough to handle these cases?

If it were impossible to know the size of a string constant supplied in
the query, then I think I would agree with you here.  However, it seems
to me that the maximum possible size of such a known, constant-width
string is not hard to determine.

> Start the width at 100, if it turns out to be too small, make it
> bigger...

If that were a good idea, then why report data sizes at all?  Just let
it always be a surprise when it comes streaming down the pipe.

Honestly, I cannot fathom this answer.