SQL/JSON: Always coerce JsonExpr result at runtime
Instead of looking up casts at parse time for converting the result
of JsonPath* query functions to the specified or the default
RETURNING type, always perform the conversion at runtime using either
the target type's input function or the function
json_populate_type().
There are two motivations for this change:
1. json_populate_type() coerces to types with typmod such that any
string values that exceed length limit cause an error instead of
silent truncation, which is necessary to be standard-conforming.
2. It was possible to end up with a cast expression that doesn't
support soft handling of errors causing bugs in the of handling
ON ERROR clause.
JsonExpr.coercion_expr which would store the cast expression is no
longer necessary, so remove.
Bump catversion because stored rules change because of the above
removal.
Reported-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Jian He <jian.universality@gmail.com>
Discussion: Discussion: https://postgr.es/m/
202405271326.5a5rprki64aw%40alvherre.pgsql