Support 'not' in many-to-many relationship (post tags)

[ErisDS]

This is heavily related to #6158, but also different 😣

---

There is currently a limitation on using 'not' when trying to posts by specific tag slugs.

Get all posts which have a given tag works: {{#get "posts" filter="tag:quick-guide"}}
Get all posts which DON'T have a given tag does not work: {{#get "posts" filter="tag:-quick-guide"}}

This bug only occurs if the posts which have the offending tag have multiple tags, if there is only one tag-per-post then it all works fine.

The reason it will not work, is that we join all tags to their posts, and then look for rows which don't match. For posts with other tags, they still get counted because they have another tag which is not the tag in question.

The solution is to use a 'where not exists' clause.

Explanation in more detail here: http://stackoverflow.com/questions/14824168/selecting-with-not-in-and-many-to-many-relationship

It's going to be important to test the combo case mentioned here pretty carefully - that is doing a 'and not' query.

[ErisDS]

I'm closing all OAuth and most API issues temporarily with the later label.

RE: OAuth, for the next 2-3 months we'll be implementing an official Ghost OAuth login system, providing global access to all Ghost blogs with a single login. We'll be opening issues around this system soon, and I don't want to cause confusion with OAuth for the API.

JSON API Overhaul & OAuth access are currently scheduled next on the roadmap

[murilobd]

I know it's closed but this bug still persists! Example:

{{#get "posts" filter="tags:-someTag"}}

If the post has multiple tags, that includes the someTag, the post will return in the search query

[naz]

@murilobd we are aware of the issue but it has been closed due to migration in progress from GQL (where the bug is present) to NQL (where we aim to have the bug fixed). The progress can be tracked here

[kirrg001]

This bug was fixed in Ghost 2.8.0.