Re: string_to_array has to be stable?

On Wed, 2010-07-28 at 20:25 -0400, Tom Lane wrote:
> string_to_array() seems fine to me: it's a predictable transformation
> from text to text. However, I think that there really is an issue with
> array_to_string(), because that takes an anyarray and invokes the array
> element's type output function.

Yes, I misread the problem because he used "current_date" rather than a
date literal.

> I can't remember offhand whether there are any volatile type output
> functions, but if there were we'd really need to mark array_to_string()
> as volatile. That would be unpleasant for performance though. I'd
> rather compromise on stable. Thoughts?

"Stable" seems reasonable to me.

A volatile type output function sounds like an edge case. Perhaps there
are even grounds to force a type output function to be stable, similar
to how we force the function for a functional index to be immutable.

Regards,
Jeff Davis