Re: BUG #17360: array_to_string should be immutable instead of stable

On Mon, Jan 10, 2022 at 7:54 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:

PG Bug reporting form <noreply@postgresql.org> writes:
> The array_to_string function should have a volatility of immutable,

Nope.  It invokes an arbitrary datatype I/O function,
which might only be stable.  As an example:

regression=# begin;
BEGIN
regression=*# select array_to_string(array[now()], ',');

That feels wrong.  It's not like we are passing the "now()" function to the function and invoking it later.  So far as array_to_string is concerned it is being given a literal value.