f6abf39ebc
Try to optimize certain types of common slow searches: * Searches for mutually-exclusive tags (e.g. `1girl multiple_girls`, `touhou solo -1girl -1boy`) * Relatively large tags that are heavily skewed towards old posts (e.g. lucky_star, haruhi_suzumiya_no_yuuutsu, inazuma_eleven_(series), imageboard_desourced). * Mid-sized tags in the <30k post range that Postgres thinks are big enough for a post id index scan, but a tag index scan is faster. The general pattern is Postgres not using the tag index because it thinks scanning down the post id index would be faster, but it's actually much slower because it degrades to a full table scan. This usually happens when Postgres thinks a tag is larger or more common than it really is. Here we try to force Postgres into using the tag index when we know the search is small. One case that is still slow is `2girls -multiple_girls`. This returns no results, but we can't know that without searching all of `2girls`. The general case is searching for `A -B` where A is a subset of B and A and B are both large tags. Hopefully fixes #581, #654, #743, #1020, #1039, #1421, #2207, #4070, #4337, #4896, and various other issues raised over the years regarding slow searches.
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.