Search by date in array of objects within PostgreSQL JSONB Column

Question

I have two tables in my PostgreSQL 9.6 instance.

users

+----+------------+-----------+-------------------+
| id | first_name | last_name | email             |
+----+------------+-----------+-------------------+
| 1  | John       | Doe       | [email protected] |
+----+------------+-----------+-------------------+
| 2  | Jane       | Doe       | [email protected] |
+----+------------+-----------+-------------------+
| 3  | Mike       | Doe       | [email protected] |
+----+------------+-----------+-------------------+


surveys
+----+---------+----------------------------------------------------------------------------------------------------+
| id | user_id | survey_data                                                                                        |
+----+---------+----------------------------------------------------------------------------------------------------+
| 1  | 1       | {'child_list': [{'gender': 1, 'birthday': '2015-10-01'}, {'gender': 2, 'birthday': '2017-05-01'}]} |
+----+---------+----------------------------------------------------------------------------------------------------+
| 2  | 2       | {'child_list': []}                                                                                 |
+----+---------+----------------------------------------------------------------------------------------------------+
| 3  | 3       | {'child_list': [{'gender': 2, 'birthday': '2008-01-01'}]}                                          |
+----+---------+----------------------------------------------------------------------------------------------------+

I would like be able to query these two tables to get the number of users who have children between certain age. The survey_data column in surveys table is a JSONB column.

So far I've tried using jsonb_populate_recordset with LATERAL joins. I was able to SELECT the child_list array as two columns but couldn't figure out how to use that with my JOIN between users and surveys tables. The query I used is as below:

SELECT DISTINCT u.email
FROM surveys
  CROSS  JOIN LATERAL (
   SELECT *
   FROM  jsonb_populate_recordset(null::json_type, (survey.survey_data->>'child_list')::jsonb) AS d
   ) d
INNER JOIN users u ON u.id = survey.user_id
WHERE d.birthday BETWEEN '2014-05-05' AND '2018-05-05';

This also uses a custom type which was created using this:

CREATE type json_type AS (gender int, birthday date)

My question is, is there an easier to read way to do this? I would like to use this query with many other JOINs and WHERE clauses and I was wondering if there is a better way of doing this.

Note: this is mainly going to be used by a reporting system which does not need to be super fast but of course any speed gains are welcome.

klin · Accepted Answer · 2018-10-10 18:46:29Z

Use the function jsonb_array_elements(), examples:

select email, (elem->>'gender')::int as gender, (elem->>'birthday')::date as birthday
from users u
left join surveys s on s.user_id = u.id
cross join jsonb_array_elements(survey_data->'child_list') as arr(elem)

       email       | gender |  birthday  
-------------------+--------+------------
 [email protected] |      1 | 2015-10-01
 [email protected] |      2 | 2017-05-01
 [email protected] |      2 | 2008-01-01
(3 rows)

or

select distinct email
from users u
left join surveys s on s.user_id = u.id
cross join jsonb_array_elements(survey_data->'child_list') as arr(elem)
where (elem->>'birthday')::date between '2014-05-05' and '2018-05-05';

       email       
-------------------
 [email protected]
(1 row)

You can make your life easier using a view:

create view users_children as
    select email, (elem->>'gender')::int as gender, (elem->>'birthday')::date as birthday
    from users u
    left join surveys s on s.user_id = u.id
    cross join jsonb_array_elements(survey_data->'child_list') as arr(elem);

select distinct email
from users_children
where birthday between '2014-05-05' and '2018-05-05';

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