ps_cart_rule_combination huge size problem

Here are the steps we worked on this issues for our customer.

1/. Backup the database

2/. import the database into Testing site, better not to touch production one.

3/. found out what kind of discount generated most of the combinat and delete them
SELECT description, count(description) as frequence FROM `ps_cart_rule` 
where cart_rule_restriction = 1 
group by description
order by frequence DESC

4/. delete from ps_cart_rule_combination where id_cart_rule_1 in (select id_cart_rule from ps_cart_rule where description like 'Birthday%');

- however, if you have a super huge like over 10G, better to Truncate All and disable the compatibility option.
update ps_cart_rule set cart_rule_restriction = 0

- most of the people misunderstood this feature(compatibility). It is no need to enable it if you assume your discount should work with any other discount. Only when you need a specific combination with two discounts.

example: You have 100 discount rules setup in the shop.

1/. customer birthday discount, 10% on specific category.

2/. Buy over $1000 with free shipping.

You still have 98 discount rules setup in the store. However, you just want customer birthday discount + Buy over$1000 free shipping can work together and nothing else.

In this situation, you will use "compatibility" to specifically declare this combination. Otherwise, it is no need to enable it.

3/. You can also disable all the expired discount rule or even delete them all. 

update ps_cart_rule set active = 0 where date_to < '2022-01-24'