在本文中，我们讨论 docs_id 选项，该选项提供了更简便的 CALL PQ 结果集操作方式。
让我们考虑以下 PQ 批量调用：
mysql> CALL PQ ('pq', ('{"title":"butter is good as", "id":3}',
'{"title":"was butter","id":4}',
'{"title":"sas was butter","id":5}',
'{"title":"bas was butter", "id":6}',
'{"title":"butter is good as","id":7}'),
1 as docs_json ,1 as docs,1 as query);
+------+-----------+------------+------+---------+
| UID | Documents | Query | Tags | Filters |
+------+-----------+------------+------+---------+
| 1 | 1,5 | butter is | | |
| 2 | 2,3,4 | butter was | | |
+------+-----------+------------+------+---------+
2 rows in set (0.00 sec)
这个输出有什么问题？
我们得到的是查询与输入数组中文档位置之间的配对列表，然而我们的文档具有一个标识符——id 属性。
如果我们希望将结果传递给下一个处理过程，就需要进行后处理工作，从输入数组中提取文档 id，使用这些位置信息。
为了避免这种后处理，在 2.7.0 版本中我们新增了一个名为 docs_id 的选项，该选项允许将文档位置替换为文档属性的值。
mysql> CALL PQ ('pq', ('{"title":"butter is good as", "id":3}',
'{"title":"was butter","id":4}',
'{"title":"sas was butter","id":5}',
'{"title":"bas was butter", "id":6}',
'{"title":"butter is good as","id":7}'),
1 as docs_json ,1 as docs,1 as query, 'id' as docs_id);
+------+-----------+------------+------+---------+
| UID | Documents | Query | Tags | Filters |
+------+-----------+------------+------+---------+
| 1 | 3,7 | butter is | | |
| 2 | 4,5,6 | butter was | | |
+------+-----------+------------+------+---------+
2 rows in set (0.01 sec)
现在我们在 PQ 结果集中获得了文档 id（或根据需要选择的其他标识符）。
所选的 docs_id 属性必须是整数属性。其值不需要唯一。例如，查询可能通过另一个整数属性进行逻辑分组。如果我们只想找出符合特定条件的组，可以使用该属性代替文档 id：
mysql> CALL PQ ('pq', ('{"title":"butter is good as", "id":3,"gid":10}',
'{"title":"was butter","id":4,"gid":20}',
'{"title":"sas was butter","id":5,"gid":10}',
'{"title":"bas was butter", "id":6,"gid":20}',
'{"title":"butter is good as","id":7,"gid":10}'),
1 as docs_json ,1 as docs,1 as query, 'gid' as docs_id);
+------+-----------+------------+------+---------+
| UID | Documents | Query | Tags | Filters |
+------+-----------+------------+------+---------+
| 1 | 10 | butter is | | |
| 2 | 10,20 | butter was | | |
+------+-----------+------------+------+---------+
2 rows in set (0.00 sec)