Creating custom event schedules. Should I use "LIKE"? - sql

Question

I'm creating a campaign event scheduler that allows for frequencies such as "Every Monday", "May 6th through 10th", "Every day except Sunday", etc.
I've come up with a solution that I believe will work fine (not yet implemented), however, it uses "LIKE" in the queries, which I've never been too fond of. If anyone else has a suggestion that can achieve the same result with a cleaner method, please suggest it!
+----------------------+
| Campaign Table |
+----------------------+
| id:int |
| event_id:foreign_key |
| start_at:datetime |
| end_at:datetime |
+----------------------+
+-----------------------------+
| Event Table |
+-----------------------------+
| id:int |
| valid_days_of_week:string | < * = ALL. 345 = Tue, Wed, Thur. etc.
| valid_weeks_of_month:string | < * = ALL. 25 = 2nd and 5th weeks of a month.
| valid_day_numbers:string | < * = ALL. L = last. 2,7,17,29 = 2nd day, 7th, 17th, 29th,. etc.
+-----------------------------+
A sample event schedule would look like this:
valid_days_of_week = '1357' (Sun, Tue, Thu, Sat)
valid_weeks_of_month = '*' (All weeks)
valid_day_numbers = ',1,2,5,6,8,9,25,30,'
Using today's date (6/25/15) as an example, we have the following information to query with:
Day of week: 5 (Thursday)
Week of month: 4 (4th week in June)
Day number: 25
Therefore, to fetch all of the events for today, the query would look something like this:
SELECT c.*
FROM campaigns AS c,
LEFT JOIN events AS e
ON c.event_id = e.id
WHERE
( e.valid_days_of_week = '*' OR e.valid_days_of_week LIKE '%5%' )
AND ( e.valid_weeks_of_month = '*' OR e.valid_weeks_of_month LIKE '%4%' )
AND ( e.valid_day_numbers = '*' OR e.valid_day_numbers LIKE '%,25,%' )
That (untested) query would ideally return the example event above. The "LIKE" queries are what have me worried. I want these queries to be fast.
By the way, I'm using PostgreSQL
Looking forward to excellent replies!

Answer 1

Use arrays:
CREATE TABLE events (id INT NOT NULL, dow INT[], wom INT[], dn INT[]);
CREATE INDEX ix_events_dow ON events USING GIST(dow);
CREATE INDEX ix_events_wom ON events USING GIST(wom);
CREATE INDEX ix_events_dn ON events USING GIST(dn);
INSERT
INTO events
VALUES (1, '{1,3,5,7}', '{0}', '{1,2,5,6,8,9,25,30}'); -- 0 means any
, then query:
SELECT *
FROM events
WHERE dow && '{0, 5}'::INT[]
AND wom && '{0, 4}'::INT[]
AND dn && '{0, 26}'::INT[]
This will allow using the indexes to filter the data.