Remove a member from multiple sets in Redis

Question

There are products and categories in my redis storage. I'm using categories sets to find products by specified category.

SADD category:1 product1 product2 product3 product4
SADD category:2 product2 product5
SADD category:5 product1 product7

Is there any way to remove a single product from all the categories except iterating over all of them? Eg some magic like this:

SREM category:* product2

Answer 1

There's no magic command.

What you could do is use (yet another) Set to track the category Sets for each product. For example, in your example you'd have to do:

SADD product2:categories category:1 category:2

And then for each of that Set's members (SMEMBERS or SSCAN to get them), do an SREM for the product from that category.

Note that while this appears to be a perfect candidate for a Lua script, it is in fact not. This is because you'd be modifying keys (the categories' Sets) without explicitly providing their names via the KEYS input construct, a shunned-upon practice that will render said script non-cluster-compatible.