SQL/JSON: Fix default ON ERROR behavior for JSON_TABLE

Use EMPTY ARRAY instead of EMPTY.

This change does not affect the runtime behavior of JSON_TABLE(),
which continues to return an empty relation ON ERROR. It only alters
whether the default ON ERROR behavior is shown in the deparsed output.

Reported-by: Jian He <jian.universality@gmail.com>
Discussion: https://postgr.es/m/CACJufxEo4sUjKCYtda0_qt9tazqqKPmF1cqhW9KBOUeJFqQd2g@mail.gmail.com
Backpatch-through: 17

Author: amitlan

src/backend/parser/parse_expr.c

@@ -4603,13 +4603,13 @@ transformJsonFuncExpr(ParseState *pstate, JsonFuncExpr *func)
 			}
 
 			/*
-			 * Assume EMPTY ON ERROR when ON ERROR is not specified.
+			 * Assume EMPTY ARRAY ON ERROR when ON ERROR is not specified.
 			 *
 			 * ON EMPTY cannot be specified at the top level but it can be for
 			 * the individual columns.
 			 */
 			jsexpr->on_error = transformJsonBehavior(pstate, func->on_error,
-													 JSON_BEHAVIOR_EMPTY,
+													 JSON_BEHAVIOR_EMPTY_ARRAY,
 													 jsexpr->returning);
 			break;
 

src/backend/utils/adt/ruleutils.c

@@ -11875,7 +11875,7 @@ get_json_table(TableFunc *tf, deparse_context *context, bool showimplicit)
 	get_json_table_columns(tf, castNode(JsonTablePathScan, tf->plan), context,
 						   showimplicit);
 
-	if (jexpr->on_error->btype != JSON_BEHAVIOR_EMPTY)
+	if (jexpr->on_error->btype != JSON_BEHAVIOR_EMPTY_ARRAY)
 		get_json_behavior(jexpr->on_error, context, "ERROR");
 
 	if (PRETTY_INDENT(context))

src/test/regress/expected/sqljson_jsontable.out

@@ -1155,3 +1155,25 @@ CREATE OR REPLACE VIEW public.json_table_view9 AS
             ) ERROR ON ERROR
         )
 DROP VIEW json_table_view8, json_table_view9;
+-- Test JSON_TABLE() deparsing -- don't emit default ON ERROR behavior
+CREATE VIEW json_table_view8 AS SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') EMPTY ON ERROR);
+\sv json_table_view8;
+CREATE OR REPLACE VIEW public.json_table_view8 AS
+ SELECT a
+   FROM JSON_TABLE(
+            '"a"'::text, '$' AS json_table_path_0
+            COLUMNS (
+                a text PATH '$'
+            )
+        )
+CREATE VIEW json_table_view9 AS SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') EMPTY ARRAY ON ERROR);
+\sv json_table_view9;
+CREATE OR REPLACE VIEW public.json_table_view9 AS
+ SELECT a
+   FROM JSON_TABLE(
+            '"a"'::text, '$' AS json_table_path_0
+            COLUMNS (
+                a text PATH '$'
+            )
+        )
+DROP VIEW json_table_view8, json_table_view9;

src/test/regress/sql/sqljson_jsontable.sql

@@ -552,3 +552,12 @@ CREATE VIEW json_table_view9 AS SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a t
 \sv json_table_view9;
 
 DROP VIEW json_table_view8, json_table_view9;
+
+-- Test JSON_TABLE() deparsing -- don't emit default ON ERROR behavior
+CREATE VIEW json_table_view8 AS SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') EMPTY ON ERROR);
+\sv json_table_view8;
+
+CREATE VIEW json_table_view9 AS SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') EMPTY ARRAY ON ERROR);
+\sv json_table_view9;
+
+DROP VIEW json_table_view8, json_table_view9;