Use a sort+compact construct instead of doing it by hand with a hashmap. The
time complexity is now O(nlogn+n) instead of O(n), and space complexity around
O(logn) instead of O(n+uniq(n)), but it shouldn't matter anyway, since
removeDuplicates is only called to deduplicate tags.
Go 1.22 introduced a new [for-range](https://go.dev/ref/spec#For_range)
construct that looks a tad better than the usual `for i := 0; i < N; i++`
construct. I also tool the liberty of replacing some
`for i := 0; i < len(myitemsarray); i++ { … myitemsarray[i] …}`
with `for item := range myitemsarray` when `myitemsarray` contains only pointers.
- `NOT (hash=ANY(%4))` can be expressed as `hash NOT IN $4`
- There is no need for a subquery operating on the same table,
moving the conditions out is equivalent.
