FOREACH key, val IN RECORD myrow LOOP IF pg_typeof(val) IN ('int4', 'double precision', 'numeric') THEN val := val + 1; -- these variables can be mutable -- or maybe in futore myrow[key] := val + 1; END IF; END LOOP;
What is important - "val" is automatic variable, and it can has different type in any step.
It is little bit strange, but impossible to solve, so we cannot to support row[var] as right value (without immutable casting). But we can do it with left value.
Actually, you can (theoretically) solve it for the right value as well with if val is an actual type and you have operators on that type that know to search for a specific operator given the actual types that are involved. So if val is int4, val + 1 becomes int4 + int4.
The problem I've run into with this is by the time you've added enough casts to make this workable you've probably created a situation where val + something is going to recurse back to itself. I've partially solved this in [1], and intend to finish it by calling back in via SPI to do the final resolution, the same way the RI triggers do.
What would be a lot better is if we had better control over function and operator resolution.
