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

1 files changed, 1 insertions, 0 deletions

diff --git a/src/include/executor/execExpr.h b/src/include/executor/execExpr.h
index 64698202a56..55337d49166 100644
--- a/src/include/executor/execExpr.h
+++ b/src/include/executor/execExpr.h
@@ -707,6 +707,7 @@ typedef struct ExprEvalStep
 		{
 			Oid			targettype;
 			int32		targettypmod;
+			bool		omit_quotes;
 			void	   *json_populate_type_cache;
 			ErrorSaveContext *escontext;
 		}			jsonexpr_coercion;