PostgreSQL-随机顺序与不同

Question

I am trying to return products in random order (or descending order) and have a button that gets more random products that are NOT part of previous random products. Basically if I have 15 products total, I want 3 random products, and then click button and get 3 more random items and so on until there are no more items.

I have a pretty whack query going on to get data from my tables.

I'm using the ' DISTINCT on ' to get one product and show it's lowest price (without it, it will list the product for however many prices it has). I know that it is effecting the random ordering / descending ordering.

SELECT DISTINCT on (products.id) products.*, prices.price FROM products
INNER JOIN product_price_size ON products.id = product_price_size.productId
INNER JOIN prices ON prices.id = product_price_size.priceId
WHERE active = true AND (archived IS NULL OR archived = false)
ORDER BY products.id, prices.price LIMIT 3

The 'get more products' button is basically the same query with OFFSET being a variable after LIMIT 3

Hopefully this makes sense. Does anyone have an idea on how to achieve what I'm trying to get?

Thanks!

Answer 1

You can keep incrementing the offset of a stable ordering. One ordering might be based on a deterministic hash like md5 (change some_random_salt for a new ordering):

select id from tbl
order by md5(id || 'some_random_salt'), id
limit 3 offset ?

Or the modulo of prime number (change the prime number for a different ordering):

select id from tbl
order by id % 11, id
limit 3 offset ?

Then increment the offset:

[...]
limit 3 offset 3

[...]
limit 3 offset 6