Tim Landscheidt <tim@tim-landscheidt.de> writes:
> It seems that XMLPARSE() is called for every row without
> PostgreSQL realizing that it is IMMUTABLE.
Indeed, the system doesn't consider it immutable. None of the examples
you show would benefit if it did, though.
I believe there are GUC-parameter dependencies that prevent us from
treating it as truly immutable, but if you want to ignore that
consideration and force constant-folding anyway, you could wrap it
in a SQL function that's marked as IMMUTABLE.
regards, tom lane