SQL NOT IN [list of ids] (performance)

Question

I'm just wondering if the amount of id's in a list will influence query performance.

query example:

SELECT * FROM foos WHERE foos.ID NOT IN (2, 4, 5, 6, 7)

Where (2, 4, 5, 6, 7) is an indefinitely long list.

And how many is too many (in context of order)?

UPDATE: The reason why i'm asking it because i have two db. On of it (read-only) is the source of items and another one contain items that is processed by operator. Every time when operator asking for new item from read-only db I want to exclude item that is already processed.

Answer 1

Yes, the amount of IDs in the list will impact performance. A network packet is only so big, for example, and the database has to parse all that noise and turn it into a series of:

WHERE foo.ID <> 2
AND foo.ID <> 4
AND foo.ID <> 5
AND ...

You should consider other ways to let your query know about this set.