Add jsonpath support for double type

Author: Nikita Glukhov

src/backend/executor/execExprInterp.c

@@ -4350,6 +4350,11 @@ ExecPrepareJsonItemCoercion(JsonItem *item, bool is_jsonb,
 			res = JsonItemNumericDatum(item);
 			break;
 
+		case jsiDouble:
+			coercion = &coercions->dbl;
+			res = JsonItemDoubleDatum(item);
+			break;
+
 		case jbvBool:
 			coercion = &coercions->boolean;
 			res = JsonItemBool(item);

src/backend/parser/parse_expr.c

@@ -4754,6 +4754,7 @@ initJsonItemCoercions(ParseState *pstate, JsonItemCoercions *coercions,
 					{ &coercions->null, UNKNOWNOID },
 					{ &coercions->string, TEXTOID },
 					{ &coercions->numeric, NUMERICOID },
+					{ &coercions->dbl, FLOAT8OID },
 					{ &coercions->boolean, BOOLOID },
 					{ &coercions->date, DATEOID },
 					{ &coercions->time, TIMEOID },