Re: ExecMakeTableFunctionResult vs. pre-evaluated functions

> Joe Conway <mail(at)joeconway(dot)com> writes:
>> If presented with a non-function-call expression tree, can we always evaluate
>> it to produce a scalar constant (if it isn't already)? If so, why not do that,
>> create a one row, one column tuplestore, and exit? It's really no different
>> than a function call that does the same, is it?

> Yeah, that's probably a reasonable approach to take. It would fail if
> we had an expression that returned a non-scalar value (viz. a set),
> but the constant-folder won't try to fold or inline anything that
> returns a set, so you shouldn't see any problem in practice.

Actually, it turns out to be easy to make ExecMakeTableFunctionResult
cope with expressions returning sets as well. It's the same as the
ValuePerCall protocol we defined for table functions (no surprise,
since that protocol was deliberately modeled on the existing
implementation of set-returning expressions). So it's done.

regards, tom lane