Re: Row pattern recognition

Hi jian,

> The comments in preprocess_expression says we shouldn't
> selectively skip constant folding for particular node fields

Agreed, and that convinces me my direction was wrong. I withdraw the
suggestion of running the pass over the argument with evaluation turned
off; nothing in eval_const_expressions() needs to change -- not a skip,
not an evaluation-off pass, not the case itself.

The reason I no longer think the case should just error is that v / 0
cannot fold on its own -- the parser requires a column reference of
every navigation argument, so int4div keeps a Var -- and it becomes
foldable only because pull_up_simple_values() has already replaced v
with Const 10, in pullup_replace_vars_callback(). So the question looks
like the substitution rather than the fold.

Best regards,
Henson