MDEV-21914 JSON_ARRAYAGG doesn't reject ORDER BY clause, but doesn't work either.

ORDER BY fixed for JSON_ARRAYAGG.

mysql-test/main/func_json.result

@@ -1240,6 +1240,9 @@ select * from v;
 JSON_DATA
 [{"type": "permPeriod", "id": "asd"}]
 drop view v;
+select json_arrayagg(a order by a asc) from (select 1 a union select 2 a) t;
+json_arrayagg(a order by a asc)
+[1,2]
 #
 # End of 10.5 tests
 #

mysql-test/main/func_json.test

@@ -759,6 +759,8 @@ create view v as (select json_arrayagg(json_object("type", "permPeriod", "id", "
 select * from v; 
 drop view v;
 
+select json_arrayagg(a order by a asc) from (select 1 a union select 2 a) t;
+
 --echo #
 --echo # End of 10.5 tests
 --echo #

sql/item_jsonfunc.cc

@@ -1452,6 +1452,52 @@ append_null:
 }
 
 
+static int append_json_value_from_field(String *str,
+  Item *i, Field *f, const uchar *key, size_t offset, String *tmp_val)
+{
+  if (i->type_handler()->is_bool_type())
+  {
+    longlong v_int= f->val_int(key + offset);
+    const char *t_f;
+    int t_f_len;
+
+    if (f->is_null(offset))
+      goto append_null;
+
+    if (v_int)
+    {
+      t_f= "true";
+      t_f_len= 4;
+    }
+    else
+    {
+      t_f= "false";
+      t_f_len= 5;
+    }
+
+    return str->append(t_f, t_f_len);
+  }
+  {
+    String *sv= f->val_str(tmp_val, key + offset);
+    if (f->is_null(offset))
+      goto append_null;
+    if (i->is_json_type())
+      return str->append(sv->ptr(), sv->length());
+
+    if (i->result_type() == STRING_RESULT)
+    {
+      return str->append("\"", 1) ||
+             st_append_escaped(str, sv) ||
+             str->append("\"", 1);
+    }
+    return st_append_escaped(str, sv);
+  }
+
+append_null:
+  return str->append("null", 4);
+}
+
+
 static int append_json_keyname(String *str, Item *item, String *tmp_val)
 {
   String *sv= item->val_str(tmp_val);
@@ -3621,15 +3667,28 @@ int Arg_comparator::compare_e_json_str_basic(Item *j, Item *s)
 }
 
 
-String* Item_func_json_arrayagg::convert_to_json(Item *item)
+String *Item_func_json_arrayagg::get_str_from_item(Item *i, String *tmp)
 {
-  String tmp;
   m_tmp_json.length(0);
-  append_json_value(&m_tmp_json, item, &tmp);
+  if (append_json_value(&m_tmp_json, i, tmp))
+    return NULL;
   return &m_tmp_json;
 }
 
 
+String *Item_func_json_arrayagg::get_str_from_field(Item *i,Field *f,
+    String *tmp, const uchar *key, size_t offset)
+{
+  m_tmp_json.length(0);
+
+  if (append_json_value_from_field(&m_tmp_json, i, f, key, offset, tmp))
+    return NULL;
+
+  return &m_tmp_json;
+
+}
+
+
 String* Item_func_json_arrayagg::val_str(String *str)
 {
   if ((str= Item_func_group_concat::val_str(str)))

sql/item_jsonfunc.h

@@ -542,10 +542,13 @@ protected:
     Overrides Item_func_group_concat::skip_nulls()
     NULL-s should be added to the result as JSON null value.
   */
-  virtual bool skip_nulls() const { return false; }
+  bool skip_nulls() const { return false; }
+  String *get_str_from_item(Item *i, String *tmp);
+  String *get_str_from_field(Item *i, Field *f, String *tmp,
+                             const uchar *key, size_t offset);
 
 public:
-  String m_tmp_json; /* Used in convert_to_json. */
+  String m_tmp_json; /* Used in get_str_from_*.. */
   Item_func_json_arrayagg(THD *thd, Name_resolution_context *context_arg,
                           bool is_distinct, List<Item> *is_select,
                           const SQL_I_List<ORDER> &is_order, String *is_separator,
@@ -560,7 +563,6 @@ public:
   const char *func_name() const { return "json_arrayagg("; }
   enum Sumfunctype sum_func() const {return JSON_ARRAYAGG_FUNC;}
 
-  String* convert_to_json(Item *item);
   String* val_str(String *str);
 
   Item *get_copy(THD *thd)

sql/item_sum.cc

@@ -3660,7 +3660,7 @@ int dump_leaf_key(void* key_arg, element_count count __attribute__((unused)),
       because it contains both order and arg list fields.
      */
     if ((*arg)->const_item())
-      res= (*arg)->val_str(&tmp);
+      res= item->get_str_from_item(*arg, &tmp);
     else
     {
       Field *field= (*arg)->get_tmp_table_field();
@@ -3669,19 +3669,10 @@ int dump_leaf_key(void* key_arg, element_count count __attribute__((unused)),
         uint offset= (field->offset(field->table->record[0]) -
                       table->s->null_bytes);
         DBUG_ASSERT(offset < table->s->reclength);
-        res= field->val_str(&tmp, key + offset);
+        res= item->get_str_from_field(*arg, field, &tmp, key, offset);
       }
       else
-        res= (*arg)->val_str(&tmp);
-    }
-    if (item->sum_func() == Item_sum::JSON_ARRAYAGG_FUNC)
-    {
-      /*
-        JSON_ARRAYAGG needs to convert the type into valid JSON before
-        appending it to the result
-      */
-      Item_func_json_arrayagg *arrayagg= (Item_func_json_arrayagg *) item_arg;
-      res= arrayagg->convert_to_json(*arg);
+        res= item->get_str_from_item(*arg, &tmp);
     }
 
     if (res)
@@ -3981,6 +3972,7 @@ bool Item_func_group_concat::repack_tree(THD *thd)
   return 0;
 }
 
+
 /*
   Repacking the tree is expensive. But it keeps the tree small, and
   inserting into an unnecessary large tree is also waste of time.

sql/item_sum.h

@@ -1924,6 +1924,11 @@ protected:
     Redefined in JSON_ARRAYAGG.
   */
   virtual bool skip_nulls() const { return true; }
+  virtual String *get_str_from_item(Item *i, String *tmp)
+    { return i->val_str(tmp); }
+  virtual String *get_str_from_field(Item *i, Field *f, String *tmp,
+                                     const uchar *key, size_t offset)
+    { return f->val_str(tmp, key + offset); }
 public:
   // Methods used by ColumnStore
   bool get_distinct() const { return distinct; }