This tag filter selects questions which match the following wildcard tag pattern:

*mail* OR rfc* OR *smtp*

The filter is returning questions tagged , which does not match any of the wildcard expressions.

Perhaps it is an unintended side effect of tag synonyms interacting with the filter algorithm. In this case someone has created a tag synonym of named . It is correct for the expansion of the tag pattern to include . But it is wrong for the filter algorithm to return questions that are tagged with , which does not match the wildcard expressions in the pattern.

  • 1
    To be honest, that seems like a good candidate for purging the weird synonym. Normally synonyms should interact with tag filters this way. Oct 12, 2016 at 20:43
  • @NathanTuggy Is it weird? I think there are a lot of related tags tied together as "synonyms" when they are not synonymous. I figured that was accepted practice.
    – MetaEd
    Oct 13, 2016 at 16:20
  • It's pretty sketchy to synonymize some random bit of PHP with PHP itself; the only reason for that is the fecklessness of askers who think it's relevant to tag some random bit of PHP. So it's basically just tag filters interacting with a hack to remove a bad tag. Oct 13, 2016 at 18:19
  • @NathanTuggy I've considered it, and I am still convinced that a wildcard search should not return results that aren't expansions of the wildcard. The filter algorithm absolutely should not match *mail* to php. The very fact that the search results can be completely bollocksed by some site's bad tag synonym shows how wrong this approach is.
    – MetaEd
    Oct 13, 2016 at 20:23
  • Well, there's certainly something deeply wrong, but I'd argue that it's at least as much a result of the inferior tag moderation tools available. Tags are third-class citizens, and boy does it show. Oct 13, 2016 at 20:54

1 Answer 1


Filter returns questions which do not match any of the wildcard expressions

This is by-design: When filtering by tags, synonyms are taken into account. If is a synonym of you certainly want to get questions when asking for : they will all be retagged .

In this case someone has created a tag synonym of php named php-mail.

should not a synonym of , they do not mean the same thing. A synonym is a word or phrase that means exactly or nearly the same as another word or phrase in the same language.

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