SQL/JSON: Fix default ON ERROR behavior for JSON_TABLE

amitlan · amitlan · commit 565caaa79af9 · 2024-09-06T10:14:01.000+09:00
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
diff --git a/src/backend/parser/parse_expr.c b/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;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/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))
diff --git a/src/test/regress/expected/sqljson_jsontable.out b/src/test/regress/expected/sqljson_jsontable.out
@@ -1150,3 +1150,28 @@ EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') ER
    Table Function Call: JSON_TABLE('"a"'::jsonb, '$' AS json_table_path_0 COLUMNS (a text PATH '$') ERROR ON ERROR)
 (3 rows)
 
+-- Test JSON_TABLE() deparsing -- don't emit default ON ERROR behavior
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$'));
+                                             QUERY PLAN                                              
+-----------------------------------------------------------------------------------------------------
+ Table Function Scan on "json_table"  (cost=0.01..1.00 rows=100 width=32)
+   Output: a
+   Table Function Call: JSON_TABLE('"a"'::jsonb, '$' AS json_table_path_0 COLUMNS (a text PATH '$'))
+(3 rows)
+
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') EMPTY ON ERROR);
+                                             QUERY PLAN                                              
+-----------------------------------------------------------------------------------------------------
+ Table Function Scan on "json_table"  (cost=0.01..1.00 rows=100 width=32)
+   Output: a
+   Table Function Call: JSON_TABLE('"a"'::jsonb, '$' AS json_table_path_0 COLUMNS (a text PATH '$'))
+(3 rows)
+
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') EMPTY ARRAY ON ERROR);
+                                             QUERY PLAN                                              
+-----------------------------------------------------------------------------------------------------
+ Table Function Scan on "json_table"  (cost=0.01..1.00 rows=100 width=32)
+   Output: a
+   Table Function Call: JSON_TABLE('"a"'::jsonb, '$' AS json_table_path_0 COLUMNS (a text PATH '$'))
+(3 rows)
+
diff --git a/src/test/regress/sql/sqljson_jsontable.sql b/src/test/regress/sql/sqljson_jsontable.sql
@@ -547,3 +547,8 @@ SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int exists empty object on er
 -- behavior
 EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$'));
 EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') ERROR ON ERROR);
+
+-- Test JSON_TABLE() deparsing -- don't emit default ON ERROR behavior
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$'));
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') EMPTY ON ERROR);
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') EMPTY ARRAY ON ERROR);

Original file line number	Diff line number	Diff line change
`@@ -4603,13 +4603,13 @@ transformJsonFuncExpr(ParseState pstate, JsonFuncExpr func)`
`4603`	`4603`	`}`
`4604`	`4604`
`4605`	`4605`	`/*`
`4606`		`- * Assume EMPTY ON ERROR when ON ERROR is not specified.`
	`4606`	`+ * Assume EMPTY ARRAY ON ERROR when ON ERROR is not specified.`
`4607`	`4607`	`*`
`4608`	`4608`	`* ON EMPTY cannot be specified at the top level but it can be for`
`4609`	`4609`	`* the individual columns.`
`4610`	`4610`	`*/`
`4611`	`4611`	`jsexpr->on_error = transformJsonBehavior(pstate, func->on_error,`
`4612`		`- JSON_BEHAVIOR_EMPTY,`
	`4612`	`+ JSON_BEHAVIOR_EMPTY_ARRAY,`
`4613`	`4613`	`jsexpr->returning);`
`4614`	`4614`	`break;`
`4615`	`4615`