Richard Huxton <dev@archonet.com> writes:
> It's not entirely clear to me why this form is different from the other form
> though.
The code that checks for expressions containing unstable functions
doesn't look inside sub-selects. Arguably this is a bug, but people
were relying on that behavior way back before we had these nice
STABLE/IMMUTABLE tags for functions. I'm hesitant to change it for
fear of breaking people's apps.
regards, tom lane
