[metrics-bugs] #23829 [Metrics/Onionoo]: Add support for search term negation

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#23829: Add support for search term negation
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 Reporter:  cypherpunks      |          Owner:  metrics-team
     Type:  enhancement      |         Status:  needs_review
 Priority:  Medium           |      Milestone:
Component:  Metrics/Onionoo  |        Version:
 Severity:  Normal           |     Resolution:
 Keywords:                   |  Actual Points:
Parent ID:                   |         Points:
 Reviewer:                   |        Sponsor:
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Comment (by karsten):

 Replying to [comment:4 nusenu]:
 > Replying to [comment:3 karsten]:
 > > Mind opening one if you think that would be a useful feature?
 >
 > #23914

 Thanks!

 > > Regarding the other parameters that you suggest that should support
 negation, that list sounds reasonable. What it does not mention is the
 "search" parameter itself, which means unqualified search terms for which
 you give use cases further down below.
 >
 > Since I realized that nickname and IP are mutually exclusive (nickname
 can not contain dots, IPs can not contain chars) it makes sense to add
 them as well even without specific IP: nickname: parameters.

 Ah! Well, you're right that nicknames and IPs are mutually exclusive. But
 other unqualified search terms are not. For example, `aaaa` could be the
 beginning of a hex-encoded fingerprint, any 4 hex character block in the
 middle of a space-separated fingerprint, the beginning of a base64-encoded
 fingerprint, the beginning of an IPv6 address, the beginning of a
 nickname, and maybe even something else I didn't think of right now. It
 would probably be very confusing to look at the results of `search=!aaaa`
 and guess which relays were excluded and why. Hmm.

 > > Before I go write more code, can you answer the following usability
 questions (numbered for easier reference, not to indicate priority)?
 > >  1. Is `!` the best character we can find to indicate negation? Or
 should we instead pick `-`? Or something else?
 >
 > `!` is IMHO the most intuitive and most common character for this use-
 case. This would be my first try before reading any documentation.

 Sounds good. I'll leave this question open here for a few more days to
 hear if somebody strongly disagrees. Otherwise it's going to be `!`.

 > >  2. We'll have to extend the various parameters to support `!` as part
 of the parameter value as in `search=flag:!exit`, and we'll have to allow
 unqualified search terms starting with `!` as in `search=!default`. But
 should we also allow qualified search terms starting with `!` as in
 `search=!flag:exit` which would be equivalent to `search=flag:!exit`? Note
 that if we do, `search=!flag:!exit` would be a valid parameter, as would
 `search=!flag:exit,guard` or `search=!flag:!exit,guard` if we extend the
 "flag" parameter as mentioned in my first paragraph. It would be up to the
 user to interpret what that might possibly mean. But maybe they're to
 blame if they write such a complex query rather than us for accepting it.
 ;)
 >
 > All use-cases can be formed with the `!` sign being used in the value
 part only, right?

 Yes.

 > `!flag:!guard,exit == flag:guard,!exit` ?

 Unfortunately, no:

 `NOT (NOT guard AND exit) == guard OR NOT exit != guard AND NOT exit`

 I'm inclined to take back the suggestion to negate search terms. If we
 limit negation to parameters like "flag", "as", and so on, that might be
 more intuitive. And we could always extend it to the "search" parameter
 later on in a backward-compatible if we change our minds. But I think we
 should start without the "search" parameter, except for values of
 qualified search terms, of course.

 Alright, I think I can work with this and write some more code. That won't
 happen today, but I'll try to do this next week.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23829#comment:5>
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