MDEV-23004 When using GROUP BY with JSON_ARRAYAGG with joint table, the

square brackets are not included.

Item_func_json_arrayagg::copy_or_same() should be implemented.

mysql-test/main/func_json.result

@@ -1366,5 +1366,21 @@ JSON_OBJECTAGG(a, e)
 DROP VIEW v;
 DROP TABLE t1;
 #
+# MDEV-23004 When using GROUP BY with JSON_ARRAYAGG with joint table, the square brackets are not included.
+#
+CREATE TABLE t1(id int primary key, name varchar(50));
+CREATE TABLE t2(id int, owner_id int);
+INSERT INTO t1 VALUES (1, "name1"), (2, "name2"), (3, "name3");
+INSERT INTO t2 VALUES (1, 1), (2, 1), (3, 2), (4, 3);
+SELECT t1.id, JSON_ARRAYAGG(JSON_OBJECT('id',t2.id)) as materials
+from t1 LEFT JOIN t2 on t1.id = t2.owner_id
+GROUP BY t1.id ORDER BY id;
+id	materials
+1	["{\"id\": 1}","{\"id\": 2}"]
+2	["{\"id\": 3}"]
+3	["{\"id\": 4}"]
+DROP TABLE t1;
+DROP TABLE t2;
+#
 # End of 10.5 tests
 #

mysql-test/main/func_json.test

@@ -856,6 +856,23 @@ SELECT * FROM v;
 DROP VIEW v;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-23004 When using GROUP BY with JSON_ARRAYAGG with joint table, the square brackets are not included.
+--echo #
+
+CREATE TABLE t1(id int primary key, name varchar(50));
+CREATE TABLE t2(id int, owner_id int);
+ 
+INSERT INTO t1 VALUES (1, "name1"), (2, "name2"), (3, "name3");
+INSERT INTO t2 VALUES (1, 1), (2, 1), (3, 2), (4, 3);
+ 
+SELECT t1.id, JSON_ARRAYAGG(JSON_OBJECT('id',t2.id)) as materials
+  from t1 LEFT JOIN t2 on t1.id = t2.owner_id
+  GROUP BY t1.id ORDER BY id;
+
+DROP TABLE t1;
+DROP TABLE t2;
+
 --echo #
 --echo # End of 10.5 tests
 --echo #

sql/item_jsonfunc.cc

@@ -3743,6 +3743,12 @@ void Item_func_json_arrayagg::cut_max_length(String *result,
 }
 
 
+Item *Item_func_json_arrayagg::copy_or_same(THD* thd)
+{
+   return new (thd->mem_root) Item_func_json_arrayagg(thd, this);
+}
+
+
 String* Item_func_json_arrayagg::val_str(String *str)
 {
   if ((str= Item_func_group_concat::val_str(str)))

sql/item_jsonfunc.h

@@ -560,15 +560,17 @@ public:
                              is_separator, limit_clause, row_limit, offset_limit)
   {
   }
-  Item_func_json_arrayagg(THD *thd, Item_func_json_arrayagg *item);
+  Item_func_json_arrayagg(THD *thd, Item_func_json_arrayagg *item) :
+    Item_func_group_concat(thd, item) {}
   bool is_json_type() { return true; }
 
   const char *func_name() const { return "json_arrayagg("; }
   enum Sumfunctype sum_func() const {return JSON_ARRAYAGG_FUNC;}
 
-  String* val_str(String *str);
+  String* val_str(String *str) override;
 
-  Item *get_copy(THD *thd)
+  Item *copy_or_same(THD* thd) override;
+  Item *get_copy(THD *thd) override
   { return get_item_copy<Item_func_json_arrayagg>(thd, this); }
 };