Select rows from a filtered portion of Table A where a column matches a relationship with a column from the row in Table B that matches by ID - sql

Question

I want to get all rows in a table where one column matches a relationship with the value of the column in the row in a different table that has the same value of another column.
Concretely, I have two tables, orders and product_info that I'm accessing through Amazon Redshift
Orders
| ID | Date | Amount | Region |
=====================================
| 1 | 2019/4/1 | $120 | A |
| 1 | 2019/4/4 | $100 | A |
| 2 | 2019/4/2 | $50 | A |
| 3 | 2019/4/6 | $70 | B |
The partition keys of order are region and date.
Product Information
| ID | Release Date | Region |
| ---- | ------------ | ------ |
| 1 | 2019/4/2 | A |
| 2 | 2019/4/3 | A |
| 3 | 2019/4/5 | B |
The primary key of product information is id, and the partition key is region.
I want to get all rows from Orders in region A where the date of the row is greater than the release date value in product information for that ID.
So in this case it should return just one row,
| 1 | 2019/4/4 | $100 | A |
I tried doing
select *
from orders
INNER JOIN product_info ON orders.date>product_info.release_date
AND orders.id=product_info.id
AND orders.region=A
AND product_info.region=A
limit 10
The problem is that this query was absurdly slow (cancelled it after 10 minutes). The tables are extremely large, and I have a feeling it was scanning the entire table without restricting it to region first (in reality I have other filters in addition to region that I want to apply to the list of IDs before I do the inner join, but I've limited it to only region for the sake of simplifying the question).
How can I efficiently write this type of query?

Answer 1

The best way to make an SQL query faster is to exclude rows as soon as possible.
So, rather than putting conditions like orders.region=A in the JOIN statement, you should move them to a WHERE statement. This will eliminate rows before they are joined.
Also, make the JOIN condition as simple as possible so that the database can optimize the comparison.
Try something like this:
SELECT *
FROM orders
INNER JOIN product_info ON orders.id = product_info.id
WHERE orders.region = 'A'
AND product_info.region = 'A'
AND orders.date > product_info.release_date
Any further optimization would require consideration of the DISTKEY and SORTKEY on the Redshift tables. (Preferably a DISTKEY of id and a SORTKEY of date).