Merge the 100 favorite subtables into a single table.
Previously the favorites table was partitioned by user id into 100
subtables to try to make searching by user id faster. This wasn't really
necessary and probably slower than just making an index on
(favorites.user_id, favorites.id) to satisfy ordfav searches. BTree
indexes are logarithmic so dividing an index by 100 doesn't make it 100
times faster to search; instead it just removes a layer or two from the
tree.
This also adds a uniqueness index on (user_id, post_id) to prevent
duplicate favorites. Previously we had to check for duplicates at the
application layer, which required careful locking to do it correctly.
Finally, this adds an index on favorites.id, which was surprisingly
missing before. This made ordering and deleting favorites by id really
slow because it degraded to a sequential scan.
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.
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