65dbd89e25
Fix the approver:, parent:, and pixiv: metatags not working correctly when negated:
* Fix -approver:<name> not including posts that don't have an approver (the approver_id is NULL)
* Fix -parent:<id> not including posts that don't have a parent (the parent_id is NULL)
* Fix -pixiv:<id> not including posts that aren't from Pixiv (the pixiv_id is NULL)
The problem lies how the equality operator is negated when the column contains NULL values;
`approver_id != 52664` doesn't match posts where the `approver_id` is NULL.
The search `approver:evazion` boils down to:
# Post.where(approver_id: 52664).to_sql
SELECT * FROM posts WHERE approver_id = 52664;
When that is negated with `-approver:evazion`, it becomes:
# Post.where(approver_id: 52664).invert_where.to_sql
SELECT * FROM posts WHERE approver_id != 52664;
But in SQL, `approver_id != 52664` doesn't match when the approver_id IS NULL, so the search doesn't
include posts without an approver.
We could use `a IS NOT DISTINCT FROM b` instead of `a = b`:
# Post.where(Post.arel_table[:approver_id].is_not_distinct_from(52664)).to_sql
SELECT * FROM posts WHERE approver_id IS NOT DISTINCT FROM 52664;
This way when it's inverted it becomes `IS DISTINCT FROM`:
# Post.where(Post.arel_table[:approver_id].is_not_distinct_from(52664)).invert_where.to_sql
SELECT * FROM posts WHERE approver_id IS NOT DISTINCT FROM 52664;
`approver_id IS DISTINCT FROM 52664` is like `approver_id != 52664`, except it matches when
approver_id is NULL [1].
This works correctly, however the problem is that `IS NOT DISTINCT FROM` can't use indexes because
of a long-standing Postgres limitation [2]. This makes searches too slow. So instead we do this:
# Post.where(approver_id: 52664).where.not(approver_id: nil).to_sql
SELECT * FROM posts WHERE approver_id = 52664 AND approver_id IS NOT NULL;
That way when negated it becomes:
# Post.where(approver_id: 52664).where.not(approver_id: nil).invert_where.to_sql
SELECT * FROM posts WHERE approver_id != 52664 OR approver_id IS NULL;
Which is the correct behavior.
[1] https://modern-sql.com/feature/is-distinct-from
[2] https://www.postgresql.org/message-id/6FC83909-5DB1-420F-9191-DBE533A3CEDE@excoventures.com
Logical
This directory contains library code used through Danbooru. This includes things like defining API clients, dealing with sources, parsing tag searches, storing and resizing images, and so on.
Many of the files here use the Service Object pattern. Instead of putting complex code in models or controllers, it goes here, in plain old Ruby objects (POROs). This keeps models and controllers simpler, and keeps domain logic isolated and independent from the database and the HTTP request cycle.