# Percolate Queries: docs_id option

In this article we discuss the `docs_id` option which provides an easier manipulation of `CALL PQ` result set.

Let's consider the following PQ batch call:


```sql
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)
```

What is wrong with this output?

We receive list of pairs between queries and positions of documents in the input array, however our documents have an identifier - the **id** attribute.

If we want to pass the result to a next process, we would need to do a post-processing work to extract the document ids from the input array using the positions.

To avoid this post-processing in 2.7.0 we added a new option called **docs\_id** which allows replacing the document positions with the value of a document attribute.


```sql
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)
```


Now we have the document ids (or other identified at choice) in the PQ result set.

The chosen `docs_id` attribute must be an integer attribute. It's values don't necessary need to be unique. For example the queries could have a logical grouping by another integer attribute. If we want to find out just the groups that match criteria we can use that attribute instead of the document id:


```sql
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)
```